Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: watson2 on December 08, 2014, 14:51:12
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Hi everybody.
My technician has just finished a complete overhaul of the engine 127.981 of my 230 SL. It was necessary for a problem with 2 crankshaft bearings.
The engine, even if broken, was silent up to 2500 rpm. Only over this speed you could hear the tipical crankshaft noise.
I have complete confidence in my tehnician; he has a great experience and he made hundreds of MB engines of every type, old or recent, and tens of engines of this type. He represents a point of reference in Milan for cars like mine. But I see him desperate because he doesn't understand.
We have a little click that is not present when the engine is cold. When the engine warms up, you can hear this noise but if we loosen a little the injector nr.6 it disappears.
Please, click the following Dropbox link to hear the noise:
https://dl.dropboxusercontent.com/u/46424947/IMG_2870.avi
https://dl.dropboxusercontent.com/u/46424947/IMG_2870.MOV (for Apple users)
It will request 10 or more seconds to be loaded
In this video we have the engine cold and the noise is 'off' but loosening the injector nr.6 it comes 'on'.
The words of the technician :"It's not possible.... I loosen just a little and the tick appears"
The noise appears if you accelerate but in video it's more difficult to distinguish it. At idle speed it's easier to appreciate it.
Have you ever heard a thing like this ?
I'll appreciate a lot your opinion.
P.S. I invite you to this link to see all the details of the overhaul:
http://freeforumzone.leonardo.it/d/10819589/Una-230-SL-a-3-posti/discussione.aspx/34
Please click on "Versione completa" (complete version) to see everything.
It's an amusing site of fans of MB's old cars. On page 34 and the previous ones you will see many images. If you want to translate the text I checked that copying and pasting the text into google translate you can understand at least the sense of the matter.
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In over 40 years of fixing cars I have never heard or seen anything like that.
The things that come to mind are a bad timing chain tensioner or the chain striking something? Maybe a loose cam or fuel pump shaft bolt?
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In over 40 years of fixing cars I have never heard or seen anything like that.
The things that come to mind are a bad timing chain tensioner or the chain striking something? Maybe a loose cam or fuel pump shaft bolt?
Thank you Shvegel for your reply. My technician says the same thing. He's becoming crazy.
The noise comes from the area of the cylinder Nr. 6 and the attention is now on its rocker arm and its pin.
These pieces are new like everything else but they are checking their fit.
We decided to change these pieces because the pins were worn after 150.000 km and they did not allow a reliable adjustment.
From Germany arrived these ones that you can see on the left. The contact surface with the cam is wider in comparison
with the old ones. They told that the new ones were Ok.
The injection pump is ok and it has been checked at least two times.
I'm sorry but maybe that in the video you cannot appreciate the frequecy of the noise.
The noise , live, seems to be similar to rocker arms' one.
I think in a few hours , maybe on monday , we will have news and I'll let you know
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Hi,
did you bleed the timing chain tensioner?
http://www.sl113.org/wiki/Engine/TimingChain
...WRe
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That certainly is strange.
It's difficult to tell from the video but am I right in saying that the noise disappears when the injector pipe is backed off?
If so then you are removed the combustion pressures from that cylinder and so unloading the piston/crank.
Did the rebuilder check the small ends?
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Hi,
did you bleed the timing chain tensioner?
http://www.sl113.org/wiki/Engine/TimingChain
...WRe
If you mean to lubricate it , I did not ask directly for this detail. So I'll do it , but I think that this operation has been made.
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That certainly is strange.
It's difficult to tell from the video but am I right in saying that the noise disappears when the injector pipe is backed off?
If so then you are removed the combustion pressures from that cylinder and so unloading the piston/crank.
Did the rebuilder check the small ends?
No, Stickandrudderman. I did not explain clearly. The noise is not present when the engine is cold ; in this case , as like as in the video, if you loosen the injector hose the noise appears.
But when the engine is warm the noise is present and loosening the injector hose it disappears. So the strangeness is that the same operation produces opposite effects depending on the engine temperature.
The details in the photo are part of the pieces we changed. I forgot: the chain and the timing gears are new.
The correction of the excessive backlashes in the cranckshaft 'shoulders' brought the values to the normal MB tolerances ( from 7 to 13 hundredths of a millimeter).
Before we could measure them with instruments used by bricklayers.
Please, look at this video to evaluate what i'm saying.
https://www.youtube.com/watch?v=HbMbpCNMq64
'Dopo Parma' means after the rectification made in Parma (a nice town in the land of engines, near Modena and famous for a delicious ham) where we took the engine after the failures of the rectification workshops in Milan.
The man we met there is a 70 years old technician that is not afraid to put his hands on the engine of a Ferrari 750 Monza or a 250 GTO.
He made a great job on the whole engine.
I invite you again to give a glance to the link of my first message (pages 33 and 34)
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I've never seen it on a petrol engine, but that test would be exactly what I would do to identify a failed injector on a Diesel engine; open the fuel line and noise disappears, close the fuel line and noise re-appears. Have you tried swapping the injector to another cylinder to see if the noise follows it?
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I've never seen it on a petrol engine, but that test would be exactly what I would do to identify a failed injector on a Diesel engine; open the fuel line and noise disappears, close the fuel line and noise re-appears. Have you tried swapping the injector to another cylinder to see if the noise follows it?
Yes, done . I think that my technician has swapped everything in the engine ;D ...
He is a wonderfull person. In any other workshop probably they had already kicked off the car ....
On the contrary he takes this like a challenge against this problem and I'm sure he will not give up until he will not have found the origin. Without charging anything to me!
He says that when the noise is 'off ' then engine sounds like a violin...
@Wre : the chain tensioner is near the cylinder nr.1 , while the noise is coming from the nr.6 , without any doubt.
The engine has been auscultated with 2 different types of stethoscope.
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I had the opportunity to go to the workshop to hear directly this noise. It's much 'deeper' than it looked in the video. It's not a tick tick ....
It seems the noise of parts of the engine like piston or gudgeon pin. It comes from cylinder nr.6 and it disappears cutting
the injection (loosening the hose of the injector nr.6 ) or the ignition (lifting the spark plug connector of the spark plug nr.6).
It's unbelievable. In the next week they will reopen the engine in search of the culprit.
I will let you know.
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I had the same exact problem. Couldn't locate barely audible soft "ticking" noise. Wasn't there when cold. Not in the newly rebuilt head. Sometimes I thought I was hearing things. But when auscultating I heard loud reverberating in some components--like the water pump--but not others and it seemed entirely random which part of the engine. Except when just listening with my ear, I kept returning to the back of the engine #5-6. Soft and deep. Removing a wire localized it to #6. I removed the oil pan and there I found "metallic paint" look to my oil, including cooper flakes, a sure sign it is a failed bearing. Unfortunately, I think you have the same issue.
Art
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By which I mean connecting rid bearing
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Rod
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Rod
Unfortunately, I have a similar suspicion, but I can't believe it.
The engine, after the overhaul has worked less than 90 minutes. How is it possible?
To undestand why I can't believe, please read again my msg #6 and visit this link
http://freeforumzone.leonardo.it/d/10819589/Una-230-SL-a-3-posti/discussione.aspx/34
The level of accuraracy was really great, but .....
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Things are evolving..... Two days ago the engine produced its noise just after the start and with a warm-up of about 1 minute the noise disappeared.
The engine was perfect for about 10 minutes. Nor idling neither over 2500 rpm the noise appeared.
After a short trip it produced again its noise, alternating moments in which it did at times when it did not .
A thing emerged: when the engine produces this noise it doesn't run 'round' , it seems to be a little 'rough'.
Now, if it was a connecting rod or a piston or a gudgeon pin this noise should be continous and not random. So we now will investigate the injection pump and the fuel . I submit that the tank has been overhauled and 'tankerized', the fuel lines (in rubber and metal) were completely replaced. In the bottom of the cup of the fuel filter we found a lot of fine grit probably coming from the rusty tank. Nevertheless it may be that there are still some 'mud' deposits in the circuit releasing fine sand that disturbs the injection. In less than 500 km we were compelled to change 2 injectors.
What do you think about these new aspects of the matter?
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Remove the oil filter and inspect between the paper to see if you have any copper metal flakes.
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No metal flakes into the filter.
An update: now the noise every day has a new way to appear. Cold engine : sometimes yes , sometimes nothing.
The same with warm engine. But now the noise can remain 'off' for a long time. Let's say that in 20 minutes of work the time
elapsed without any noise is much more then the time during which the noise is audible.
And when the noise is audible may be it's loud so as at the beginning of this arcane, but may be also that it's much lower in terms of intensity.
My technician was one of the first persons to make training on Bosch injection pumps many years ago , but anyway we asked a consultation
with other 2 Bosch experts. Many brains and many ears could obtain better results than one.
The matter is assuming worrying aspects, but it is intriguing....
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The "break-in period" just after major engine work is the most critical and most vulnerable period. Any mis-alignments, mis-torques, incorrect machining, incorrect parts, improper assembly, can cause failure. Dirt or contamination lurking in numerous hidden passages can dislodge and cause problems. Watson, I wonder if a valve guide or valve seat is randomly coming loose in the cylinder head. This would cause a noise which may come and go randomly. Either one of these problems could cause a rough running situation to occur when the noise appears. If so head removal may be a much easier fix than a bottom end problem. You may be able to take a bore scope into the cylinder and inspect the combustion chamber in the head for signs of a loose valve seat. You may also have some marks on the top of the piston.
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Thank you ja17. We will take a bore scope and I'll let you know as soon as possible. Meanwhile the technician is planning to reopen everything again, and see if there are signs
I take this opportunity to warn the member who sent me a private message that the system does not allow me to send my answer because strangely it tells me that cannot be found the userid with which the message was sent to me.
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I spoke to my technician and he said that the engine was already 'borescoped'.
With a device with a view to 90° it was easy to observe every interior detail of all the cylinders.
No visible defect
Meanwhille the noise is changing : loud , not audible, clicking, like a hammer . Depends on the moment.
Probably it is something that can move and can change position at any moment. The only pieces that can do this are the piston pins or their bushings.
If nothing changes in a few days the engine will be opened again....
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Valves rotate as well as oscillate. A rotating valve that is not seating properly might well give symptoms that come and go but it tends to be uniform in its pattern.
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Continuing with Stick's idea........................ A slightly bent valve stem could be causing the valve to stick open. Then the piston rises and slams it shut.
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Watson says the engine( I assume each cylinder) has been bore scoped, if so then any damage to the piston from a valve would have left a mark and have been seen by the operator.
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I had a car in that had a clicking noise that seemed to be louder at times than others but it was always there. Adjusting the valves really didn't change the noise. Eventually the engine swallowed a valve and smashed a piston. Turned out one of the valve keepers were worn just enough to be noisy but very hard to actually detect the problem. Common things are common but this isn't common in 230SL engines. I'm sure PJ will post a pic of the damaged piston.
In a different note, I have a 280SL in that's making no noise at all. Seems the timing chain broke. I've never seen this before in nearly 40 years of working on these cars. The chain was tight when we set the valves and it wasn't making any noise. Odd thing is that the thrust washer that sits behind the distributor drive gear broke into several pieces. This is a fairly heavy part made from good steel and I can't figure out what made it break. I'm pretty sure that a broken piece of this washer fell into the chain causing it to break but it's still unclear as I don't have it all apart yet.
The head isn't damaged and nothing hit the pistons so it won't be too bad as far as repairs go.
I have a hunch that the drive gear that runs the tach and oil pump was probably loose and somehow this caused things to fly apart because the gears were barely in mesh when I inspected them. Clearly, someone had the engine apart but didn't get the small details covered.
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Stick's comment triggered an old memory. I had a '72 250C (M130 carb engine) that had a similar noise. It would go from quiet to a barely audible tick, to a click, and then a clack, then back to quiet. I did some research (pre-internet) and learned that rotating valves had been a feature of Mercedes engines forever. I concluded that I had one valve/rocker that changed clearance as the valve rotated. I was never able to fix it.
Cheers,
CT
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Hi guys . Thank you for your help.
I hope this helps to understand why i define this noise curious…
https://www.dropbox.com/s/lj07ul6omk1qqdh/Engine_noise.m4v?dl=0
Please wait some seconds while loading.
Now it seems a bad, bad noise, when present.
Monday morning the engine will be opened again (sic)
I will let you know the results
P.S. ...but if you have any idea , please tell me…
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That's a tappet noise.
Do you get an associate misfire when that noise is present? If so then you have a sticking/bent valve or loose seat.
If no misfire then it's probably a fatigued anti-rattle spring (or incorrectly fitted) of less likely a worn tappet post.
Either way it doesn't sound as serious as first thought.
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Yes, most likely a valve train problem. Loose valve seat, or guide and/or bent valve. You may even notice one spring assembly sitting lower when you remove the valve cover.
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Going on what Chuck said, it could be a broken roto cap. It sticks in one spot and then lts go causing noise for a while until it locks p again. You could remove the rockers on that cylinder and tap the valve retainer which will make the valve spin. If it doesn't turn or it stops turning that could be the problem.
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That's a tappet noise.
Do you get an associate misfire when that noise is present? If so then you have a sticking/bent valve or loose seat.
If no misfire then it's probably a fatigued anti-rattle spring (or incorrectly fitted) of less likely a worn tappet post.
Either way it doesn't sound as serious as first thought.
Hi Stick .
I thank you for your post. No misfire at all. Someone told that the engine seemed rough when the noise is present, but I never heard directly this.
The valves have been buffed (I hope that this is the exact word in english) and , as you can see in the previous page in my message nr.3, the rockers arms , screws and balls are new.
The valve guides are new and verified
Using the attached image , please, can you indicate the number corresponding to the anti-rattle spring and to the tappet post ?
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Going on what Chuck said, it could be a broken roto cap. It sticks in one spot and then lts go causing noise for a while until it locks p again. You could remove the rockers on that cylinder and tap the valve retainer which will make the valve spin. If it doesn't turn or it stops turning that could be the problem.
Excuse me Benz Dr. , but my english , above all the technical one, isn't good enough to understand a lot of terms. Looking at my posted image , which number has the roto cap?
And the valve retainer is the nr.82 ?
Thank you for yo help
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Roto cap (essentially a bearing) is no 73 and valve retainers no. 82.
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The roto cap or rotator cap is a device that makes the valve spin as it moves up and own. I believe there are a number of ball bearings inside and a series of notches that the balls fit into that allows movement only in one direction. If you remove the oil fill cap on a running engine you can actually see the valve retainer slowly turning at idle speed which means the roto cap is working on that valve. I check them during a head rebuild by tapping on the retainer which should make the valve spin. I've seen them bind up and quit working possibly due to wear or rust from prolonged storage.
If you can locate which cylinder is causing the noise you may be able to do the test I suggested.
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Using the attached image , please, can you indicate the number corresponding to the anti-rattle spring and to the tappet post ?
I guess anti-rattle spring is no 94 and tappet post no 92.
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Cees wins!
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Any news on the engine noise?
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Hi guys. I was waiting for results.
The engine has been deeply inspected and the only thing that has been found is an augmented play of one of the valves of the cilinder nr.6 in its giude.
So the remedy put in place in an attempt to eliminate the noise has been a new set of 12 valve guides; as a matter of fact during the overhaul they changed the valve seats but not the guides. :o
Just tomorrow morning reassembly of the engine will be started. I will let you know when the key will be turned...
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An engine overhaul that didn't involve new valve guides? ???
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Double check the valve seats. Valve guides do not normally make noise when they go bad.
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An engine overhaul that didn't involve new valve guides? ???
When I knew this I was amazed as much as you.
Look at my msg....
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Hi guys. Here we are. The engine was finally started and , at this moment, has done about 400 Km. The sounds you heared are gone, but I can not say that it is perfectly silent. There remains a slight background noise that could depend by the play of the valves.
But I'm afraid that it could depend on the compression ratio.
Even if the piston have been reduced on their head for 5/10 of mm. the value of the compression remained high (about 10:1 in comparison with the original value of 9:3).
I examined the image of the head of another car (a 280 Sl, I suppose) and you can see it as the first one of the 3.
The second image belongs to my engine before any work.
The third one is always the head of my engine , but after grinding works. (correct term?)
What do you think about this last aspect of the matter?
Have to look for a new head? Do you think that gaskets with increased thickness could represent a good remedy?
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To my untrained eye it would seem too much of the head was removed (I believe the term is 'skimming'). The shape of the combustion chamber is quite different from before.
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I would concur with Cees. They seemed to have removed way too much metal form the head. If I see correctly, the exhaust valve is out of the combustion chamber.
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May just be an optical illusion. Measure the thickness of the head to be sure. The ends seem to get cut the most.
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The flame front propagates in every way 'cause the roof of the piston has been turned. In this way the path of the flame isn't certainly the one of the project. My consolation is that I see on the german site of SLS-hh that they use in their e-shop an image like mine to show the piece in question.
I asked to the technician and he said the the height of the head is within tollerance.
Anyway I'll begin to look for a new head....
The engine has an uncertain idle and we found the spark plugs in this situation.
The spark plugs are from 1 to 6 from left to right. Every cylinder is linked to the corresponding spark plug. The cylinder 1 has a dirty spark plug, but the piston head quite clean while other cylinders have the spark plugs clean but the heads of the pistons encrusted. What do you think? Have I to change injectors? They suggested to me to change all the injectors. To avoid to throw away money... sure all?
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You say your mechanic says the head is within tolerance, what cylinder head thickness is he using?
You could move the injectors into different cylinders to see if the pattern repeats itself, or get the injectors tested on the correct machine.
Also you could purchase a burette and see if all your combustion chambers are equal and with this information calculate your compression ratio.
I have the (standard) volume of the combustion chamber of the type of cylinder head that you have, if you decide to go down that route.
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Watson, how did you determine you now have a 10:1 compression ratio?
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I would say that you have a problem with injector #1, and that you are running a bit lean. I would go two clicks rich on the rack, and adjust the idle mix as needed.
Autohausaz.com has injectors for $103 apiece, and offers discounted international shipping.
Good luck.
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Hi guys. Excuse my absence.
@tel76 : my mechanic has a table with all standard measures of the parts of the engine. I refer what he said and I have to trust what he says.
We calculated a volume for the 230, in original conditions, of 41,2 cc. (about 2,5 cubic inches) . Is it correct?
@GGR : the mechanic showed to me a pink chart done with the usual little tool made to measure the ratio.
I think that the value is not too high, all things considered, for the 5/10 lowering of the pistons; with this value we regained 2,67 cc (0,162 cubic inches)
@ctaylor738 : I am in accordance with you and so we are waiting for new injectors (Bosch 437 004 002) . We found for 87,5€ incl.tax in Frankfurt at Partsrunner.
News as soon as possible.
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Hi guys.The injector nr.1 has been changed. This is the plug nr.1 . Now the engine runs much better, no bang, no uncertain idle. But it still remains noisy, especially accelerating during normal use . It's not the noise I heard on other 042 engines. I observe with suspicion the head....
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I would concur with Cees. They seemed to have removed way too much metal form the head. If I see correctly, the exhaust valve is out of the combustion chamber.
I see the exhaust valve on the left in the photo near the plug. So the valve out of combustion chamber is the inlet one, on the right. But the side is not relevant. The real problem is that the chamber is too little.
Do you think a thicker head gasket could work? Which are the problems of this type of gasket?
I calculated that we could increase the volume of 5,3 cubic centimeters (= 0,325 cubic inches) for each mm. of thickness.
@tel76 : could you kindly tell me if the calculations about the volume of the combustion chamber were right?
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Did anybody ever record the head thickness in various places?Are you below minimum thickness? Also certain areas of the combustion chamber can be "carved-out" to provide more volume. It is a common procedure when "blue-printing" engines. The volume of the combustion chambers can be adjusted, measured and matched exactly. Two head gaskets would be very risky on these engines since the space between cylinders is so minimal. I don't think they would hold up.
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These are not the quietest engines ever made.
When you say "noisy," on normal acceleration, what do you mean? Is it "pinging" aka pre-detonation, which is sort of a sharp rattle like rocks in a tin can? Or some other kind of noise?
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These are not the quietest engines ever made.
When you say "noisy," on normal acceleration, what do you mean? Is it "pinging" aka pre-detonation, which is sort of a sharp rattle like rocks in a tin can? Or some other kind of noise?
I knew a guy once who was about as sharp as '' rocks in a tin can. '' Does that count? ;D
Measuring a cylinder head seems simple enough but we often cut the top of the head to make it straight and level with the bottom of the head. This would leave the impression that the head is under the minimum 84.00 mm spec and yet it isn't. Most cylinder heads are also warped on the top surface as well as the bottom. You can straighten a cylinder head by heating it in an oven and pulling it straight. Done properly, only a minimal cut is required to make it level again. The top of the head should be checked and planed as well if needed.
I use .015'' cam bearing shims to compensate for removed material because the valve stems will sit higher after any material is removed from the top of the head. Since you need a minimum of .050mm intake valve recession, the valve seat sometimes needs to be cut deeper to adjust this measurement. This will also cause the intake valve stem to rise which can lead to rocker geometry problems. By raising the cam shaft with shims under the cam bearings, you can compensate for deeper valve seats and any removed material from the top of the cylinder head. A standard lash cap is 4.5mm and if you run out of ball stud adjustment using this part you can get ones that are only 2.5mm. I generally never use more than two cam shims per cam bearing (.030'' ) and if I still have adjustment problems then I use a thinner lash cap.
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Head thickness measurement is still a good gauge since material cut from the bottom of a head is cut at each end and most material cut from the top is central. So theoretically a head warped .020" will get .020" cut at the ends on the bottom. On the top it will get cut .020" in the center and you still end up with a flat head cut .020" overall. The bad thing is you get very high compression on the end cylinders. Dan, are those camtower shims something you can order or do you make your own? I've always had to make them, but would rather buy them.
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Joe,
Metric Motors sell them in different thicknesses, you do have to modify the rear one to allow the oil to drain back into the sump.
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Thanks Eric.
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Joe,
Metric Motors sell them in different thicknesses, you do have to modify the rear one to allow the oil to drain back into the sump.
This is news to me. Mike never mentioned it, which I expect he would have if it was important, and I've never done it myself. Odd that nothing has blown up yet. :) These shims are made in the same shape and dimension as the bottom of the bearing so I'm not sure how they could close off the drain hole for the oil return. Am I missing something here?
Shims come in different thicknesses up to .015'' which is what I use. They are stainless steel and well made. Less than 10 bucks each.
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I checked out the cam shims on the last bearing and yes, on some engines the valley below the bearing isn't that deep and it may cause a restriction of sorts. Any extra return oil would run down the chain case so I don't think it's a really big issue.
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It would be a very big problem, the front of the engine is higher than the rear so if the oil cannot get down the rear oil return hole a large pool will develop in the rear of the rocker cover, this could/would compromise the rocker cover seal resulting in an oil leak. The rocker cover seal is not intended to hold back a large quantity of oil.
I should also have mentioned that if the oil cannot drain at the rear of the engine and the pooling accurse then the rear cylinder valves springs and oil seal are fully immersed in oil, the seals cannot cope and oil will enter the cylinder or exhaust tract resulting in smoke.
MB were aware of this problem ( caused by the block drain hole being too small) and during this engines production run the rear oil drain in the block was enlarged.
At the time it was not unknown for some engines to be stripped down only to find that there was nothing wrong.
Perhaps Achim will have information on when this change happened.
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Maybe. I've never done this small mod and none of my rebuilds leak at the back of the engine. A lot has to do with the cylinder head casting and if this is such a big problem why have I never seen it before? And believe me, I check everything very closely before it leaves. If anything, not adding shims when you need them is a far bigger issue.
I will however, check this out in the future.
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These are not the quietest engines ever made.
When you say "noisy," on normal acceleration, what do you mean? Is it "pinging" aka pre-detonation, which is sort of a sharp rattle like rocks in a tin can? Or some other kind of noise?
It's difficult for me the description of this noise , expecially in a technical language that I don't know with richness of terms . So I will provide an audio record to allow you to listen the noise.
I asked to two engine experts an opinion about the noise. Both told that the noise is coming from the rocker arms ; in relation to the frequency of the noise they told that both have ventured that could come from one or two tappets, and the noise is anyway coming from the high part of the engine.
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Hello watson,
Sometimes after cylinder head repairs you can get a very hard-to-find, elusive noise from the valve train. During cylinder head repairs, the valves and their seats are ground and as a result, they sit higher in the cylinder head. As a consequence, the rocker arm may be contacting the upper spring retainer before actually hitting the valve shim. This happens at the arch of the rocker arm where it passes over the upper valve retainer. The contact causes a "tappet type noise". Look closely for any rocker arms which are suspicious and examine the "arch". You will see sings of contact if this is the case. Grind the arch slightly and your noise will disappear. Also any place where a thinner than standard "pressure piece" was used, is more likely to be the culprit.
There is a danger if this is the case and it is left un-fixed. The early contact to the upper spring retainer slightly loosens the valve keepers for an instance on every revolution. Eventually a valve, in the cylinder head, could be released and be sucked into the engine, causing catastrophic failure.
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Second what Joe said. I fixed a 230SL where the valve dropped into the cylinder because of this. It was a complete mess.
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Second what Joe said. I fixed a 230SL where the valve dropped into the cylinder because of this. It was a complete mess.
Me too. And it was a 230SL.............
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Hello watson,
Sometimes after cylinder head repairs you can get a very hard-to-find, elusive noise from the valve train. During cylinder head repairs, the valves and their seats are ground and as a result, they sit higher in the cylinder head. As a consequence, the rocker arm may be contacting the upper spring retainer before actually hitting the valve shim. This happens at the arch of the rocker arm where it passes over the upper valve retainer. The contact causes a "tappet type noise". Look closely for any rocker arms which are suspicious and examine the "arch". You will see sings of contact if this is the case. Grind the arch slightly and your noise will disappear. Also any place where a thinner than standard "pressure piece" was used, is more likely to be the culprit.
There is a danger if this is the case and it is left un-fixed. The early contact to the upper spring retainer slightly loosens the valve keepers for an instance on every revolution. Eventually a valve, in the cylinder head, could be released and be sucked into the engine, causing catastrophic failure.
When we changed the pins and the rocker arms this problem was detected 'on the table' and, I'm not sure, but they installed a piece that could be the nr.85 in the following picture. It was a little thicker to avoid the contact, it seems to me.
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Looks like your onto something. Go back and check the rest.
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If the rocker geometry is right it won't hit anywhere. How much thread do you have showing on the ball stud pin?
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If the rocker geometry is right it won't hit anywhere. How much thread do you have showing on the ball stud pin?
I have only this image showing the detail that you want to know (if I have understood your question).
No thread is visible, but the the right pin is a little taller.
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Those are very low - probably within less than a turn before they bottom out. I prefer to see a couple of threads on the ball stud showing above the base portion so that the rocker arm is sitting in the right plane. One or two cam shims would cure this problem and that's only if the valve guides aren't already damaged.
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Here it is the file that I prepared. No sophisticated devices, only an Iphone.
I captured this video with both side windows open and the phone near the left window. Walls around the car and a small climb to overcome to make a bit of effort to the engine are all expedients to increase the audibility of the noise .
When the engine is warm the noise doesn't change.
I inserted a detail of another problem I have on my 230 with automatic gearbox.. The video shows the taco increasing and decreasing the rpm for 500 units. When I push the brake the rpm increase , when I release the pedal the rpm return to normal. An information : the servo is not working properly. is it possible that the engine take air through a broken membrane ?
Excuse the quality.
The video will take some seconds to be loaded.
https://www.dropbox.com/s/8gn8wlrw3t7ef69/IMG_3252%20%281%29.mp4?dl=0
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Those are very low - probably within less than a turn before they bottom out. I prefer to see a couple of threads on the ball stud showing above the base portion so that the rocker arm is sitting in the right plane. One or two cam shims would cure this problem and that's only if the valve guides aren't already damaged.
This is due to the fact that the valves sit higher?
And also the thicker piece nr 85 I think has played the same role.
Tell me , please, where I could buy the 0,015" shims.
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This is due to the fact that the valves sit higher?
And also the thicker piece nr 85 I think has played the same role.
Tell me , please, where I could buy the 0,015" shims.
Yes. As the height of the valve stem increases the height of the rocker arm must decrease in order for you to obtain the desired clearances of .003 and .007'' Once you get the ball end of the rocker that low, it will deflect the valve stem sideways and take out the valve guide/s. The exhaust guides tend to wear at a faster and higher rate possibly due to the larger and thus heavier diameter of the stem. In other words, the valve stem won't bend and all that force has to go somewhere. Once I figured this out many years ago my rebuilds became much better. By raising the cam shaft you have to raise the valve adjuster with it and the ball end of the rocker arm moves up. This isn't a one to one ratio but it's likely more like a two to one figure. The rocker is actually a lever and it will do a proper job once it's set up properly.
I should have a few cam shims here or you can get them from Metrics.
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Thank you Benz Dr for the clear explanation, thank you indeed.
Two remarks: the difference between brake pedal Up and pedal down is so remarkable with cold engine. With warm engine the difference is of 100 rpm. A phone headset could be usefull to emphasize high frequency sounds
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Your brake booster could be starting to fail. I've changed a lot of them over the years.
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Your brake booster could be starting to fail. I've changed a lot of them over the years.
Yes , I think so.
Nobody has an opinion about the noise in my msg #70 ?
P.S. I'm a Ferrari fan since my childhood and I have a 246 gt since 1971. So, please, authorize an 'out of theme' : let me rejoice fot Sepang and Losail victories. It was time !
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Still think its an issue with the rocker arm double contacting (message #62).
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Flavio,
You can post a picture of your Ferarri in the “Other Cars” area of the forum. :o;D ;D
Garry
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Still think its an issue with the rocker arm double contacting (message #62).
Hi Joe. Your message #62 was read with great attention and it was object of discussion. My mechanic, as I told you some pages ago, knew the problem and avoided contacts with a thicker device nr.85 in the pevious drawing. But so this solution has brought the arm too low on the ball pin side, so as Benz Dr. has remarked. Just tomorrow (I'm tracking the package) I'll have 8 shims purchased by Metric. I hope that these tribulations have end ...
@Garry : thank you, Garry . I did .
P.S. you live in a beautifull country. I was there in September 2013 and I was fascinated with the nature, the the serious organization of your state apparatus , the people and their friendliness. Beautiful places, beautiful people .
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As long as the valve guides haven't been damaged the cam shims will probably do the trick.
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Measuring a cylinder head seems simple enough but we often cut the top of the head to make it straight and level with the bottom of the head. This would leave the impression that the head is under the minimum 84.00 mm spec and yet it isn't. Most cylinder heads are also warped on the top surface as well as the bottom. You can straighten a cylinder head by heating it in an oven and pulling it straight. Done properly, only a minimal cut is required to make it level again. The top of the head should be checked and planed as well if needed.
Your informations are absolutely priceless. But I would like to have some more information about the procedure to pull the heads straight. If you can say something more about the oven, the temperature to be reached, the physical way in which the head is straightened and if the workshop where this work is made is a grinding workshop or not. In short, as many details as you can.
Thank you.
P.S. The shims are here . 7 days from CA.
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I'm going by description here because I've never actually seen this done.
Basically, you strip the head of all parts, place it in an oven and put two steel blocks under each end of the head. This will leave the middle of the head unsupported which is what you want.
In the middle of the head, or where the warp is highest, you place another bar across the top of the head from side to side. This bar will have a hole on each end where threaded rods run from the floor of the oven, through the holes in the bar and are held in place by nuts and a washer. By tightening the nuts and heating the head you pull the head straight again. Anything over .010'' warp will probably take two heatings. I was told that it gets pullled a little bit past straight because it will pull back up due to elastic memory.
I'm not sure how hot they set the oven but 300 degrees F seems to stick in my head. This isn't like your oven at home - it's designed for this kind of work so don't even think about trying it yourself. The head is cleaned first and prepared properly. This is the only way to deal with a warped head. Once straighted it may only take a .005'' cut to smooth the surface. Cutting the head without straightening first will leave it milled heavily on each end ( number 1 and 6 cumbustion chambers ) and reduce the service life of the head. What could take several small cuts over many years would now be reduced to two or three if milled when warped.
What many places tend to miss is the fact that the top of the head may also be a mess and it will need to be planed as well. This is where cam shims become vital. Anything you remove from the top of the head or the valve seats has to be added back to base measurements. Planing the top of the head can save you the possibility of breaking a cam and destroying other nearby parts. After you have your cam tightened down ( full torque ) it should move freely by hand if everything is right. If it won't move freely the head is probably not straight so take it back off and start over again.
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Great Benz Dr. ! No, I'm not going to make this by myself. Simply when I'll meet my next ;) head , I will be able to explain to someone what could be done in case of warping. Thank you for your detailed explanation.
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Joe,
Metric Motors sell them in different thicknesses, you do have to modify the rear one to allow the oil to drain back into the sump.
I attach here an image of one of the shims with numbers in several areas. If you don't want to modify the image with your drawing, can you tell me , please , where and how we have to pay attention for the passage of the oil . When you say rear you mean the last one near to cylinder nr. 5 and 6?
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Yes, the rear of the engine near the bulkhead.
Place the shim into position(without the camshaft bearing) and you will see if there is an adequate space available for the oil to drain down the hole at the rear of the cylinder head into the cylinder block, it is very noticeable if the shim blocks the oil drain passageway, you just cut the shim to allow the oil to drain, Dan C did indicate that not all heads had this problem.
Is your engine in the car or out?
I had to obtain another cylinder head for my engine, with this replacement cylinder head i had to carry out the shim modification, I will look at the old cylinder head from the 1970 280sl tomorrow and determine if the modification would have been required.
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Thank you Eric. The engine in this moment is on the car. They will set the play of the tappets and will give again the correct torque to the head
The positioning of the shims will not require to pull out the engine.
By the way . I will not accept to have an head like mine, without a proper combustion chamber. If anyone has a head for the 230 please tell me.
I found one in good conditions. But it was of an egnine with carburators. I dont think that I'll find anyone that will make the holes and threads for injectors.
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Watson, the fuel injected head has a much wider chain gallery than the carbureted heads. A carbureted head cannot be used.
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you do have to modify the rear one to allow the oil to drain back into the sump.
I looked at the detail you mentioned on a 280 head and I found 'the hole'. If the 230 head has the same passage,
is it enough to cut , i.e., the 50% of the shim to allow the passage of the oil or is it necessary a cut in the whole width?
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Is it possible for you to fit the shim and post a picture ? or trim the shim to match the contours of the camshaft tower/bearing.
With the shim in position does it restrict the oil return hole?
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Is it possible for you to fit the shim and post a picture ? or trim the shim to match the contours of the camshaft tower/bearing.
With the shim in position does it restrict the oil return hole?
Excuse me Eric. Sorry for the late response
The car is 55 Km far away and so I cannot make the foto when the shims will be put in place. I can ask to the mechanic to make it for me, if he will remember to do it.
But I think that it will be necessary to cut a large part of the shim, if the hole in 127.981 engines is the same.
I will inform you about the installation.
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Well, the car is at home ...
The after 1500 Km the correct torque of the head has been renewed, the tappets have been verified and the shims got by Metric were installed (0,35 mm) .
The brake booster overhaul had a good result: when the brake pedal is pressed that 500 rpm augmentation is disappeared. No changes in rpm.
The engine is only a little less noisy. But there are many reasons to make me a little sad: the noise that the engine produces is different every day
and speaking about mechanics this is not a good sign. The engine doesn't idle smooth , it's a little rough and has a reduced sensibility to the air screw movement.
The car runs in a good way between 1500 and 4000 rpm, and when you stop the car, the engine can run at 800 rpm for minutes without problems.
But as the engine drops under 700 rpm it looses 1 or 2 cylinders. You can hear the tipical rattle of an engine without one or two cyl.
One of these times in which the engine is not running smooth I stopped the engine and I watched the plugs. and this was the look.
They are almost white. Non one is dirty. What is happenig?
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Ohhhhh.......... that's lean! :o
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Have you considered taking the car to a different specialized mechanic? It seems your current one has exhausted his knowledge but there are still some issues to be sorted out. Perhaps it's a few minor things that need the experienced eye to sort out. What we don't want is for something major to happen to the engine because of some relatively minor issue as described by Joe, Dan and others. Sorry I can't be more helpful but for peace of mind I would take it to someone else at this stage.
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Indeed, I would suggest you find someone endowed with significantly more competence than your current supplier of services.
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Yes Cees and yes Stick. You find me in complete accordance with you!!! The noise , other details , and after the matter of the valve guides I began to have a suspect. Now the things tell to me to do what you suggest. I already phoned to a specialist ( ;D) in Brescia that was named by my friends. In these days he is not in his workshop because he was called by someone in the Mille Miglia race. I have an appointment monday morning.
The workshop is 150 km from Milan but I hope it's worth to do some kilometers.
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He will probably tell you that you are running lean and suggest going a couple off clicks rich on the main rack adjustment. You could try that yourself and see if it helps.
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He will probably tell you that you are running lean and suggest going a couple off clicks rich on the main rack adjustment. You could try that yourself and see if it helps.
Done, Chuck. I gave 5 clicks clockwise and nothing changed. A friend of mine (old MB mechanic now retired) has a CO meter and he came to my house for a 'home visit' at the bedside.
I don't know if that machine was correctly working , but the display initially marked 0.4. After the 5 clicks the value was 0.9 .
When I kept the car on saturday the mechanic spoked about 2.5 . :'(
There is a low sensibility to the changes of the screw of the air on the intake manifold.
Now the engine is even worse. It sounds as if there was a valve opened.....
TO morrow I return for the last time to Milan. After this I will stop.
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I think maybe you might be turning the idle mixture knob on the back of the pump when it's a screw inside the back cover that's being referred to?
I've been using the barometric compensator for major mixture changes with pretty good sucess. It's a whole lot easier to get at and fairly easy to adjust once you figure out how it works - if in fact it really is.
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Agree with Dr. Dan. Adjusting the idle mixture is not going to solve your problem.
You are lean on the main rack setting, that's why you can't get the idle CO up to at least the 4% needed to idle well.
The main rack adjustment is done by removing a screw on the back of the pump and inserting a long, thin flat screwdriver in the hole. Once you find the adjusting screw, you push it in to engage the adjuster. It is the opposite of the other adjustments. Left is rich, right is lean. The procedure is described in the Technical Manual and the Haynes manual.
Dr. Dan's method of unscrewing the barometric compensator will achieve the same result, but I think the main rack adjustment is the proper way to go.
The main rack adjustment will richen the mixture under all conditions, so then you can adjust the idle mixture with the external thumbscrew.
I have observed that rebuilt pumps need 1-3 clicks rich to get the car to run right.
Cheers,
CT
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The compensator works the same way in that it affects all mixtures across the entire range. If you run out of adjustment on the idle mxture knob and your idle mixture is still too rich, then the rack will need to be moved to a leaner position. This adjustment will give you a lot more room on the mixture knob when you had none before.
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Also, make sure to never fiddle with the idle adjustment knob with the engine running, or you will damage the mechanism.
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Also, make sure to never fiddle with the idle adjustment knob with the engine running, or you will damage the mechanism.
Thank you GGr. Every time the engine must be stopped before touching the pump's knob.
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Excuse me if during the next discussion I'll use incorrect terms , but my technical english is even worse , if possible, than the not technical one.
Well guys. Against all odds , the behaviour of my mechanic has been very professional.
The car arrived to the workshop with a 5 cylinders idle. If I accelerated up to 2500 rpm the engine was running better, but just a few seconds later it returned to 5, if idling.
Manouvers and effects : removing the spark plug cap of the cylinders 6, 5, 4 the engine went with 4 cyl. The same with 1 and 2. But with the absence of the cap nr. 3 there were no changes. Always 5 cyl.
The spark plug was dirty, black and with a lot of charcoal deposits .
New spark plug into cylinder nr.3. Starting again the engine , just in a few seconds it was evident that nothing was changed : 5 cylinders again.
Then the wire nr.3 was tested and the spark of nr.3 was verified. If was strong. No problem with ignition system.
So the attention moved onto the injectors.
The injector nr.3 was exchanged with nr.6. No changes . The cylinder that produced the 5 cyl rithm was always the nr.3.
So the injectors are not guilty.
Probably there is something into the injection pump the doesn't work correctly : the valve that guides the fuel spot is not closing correctly. It could remain opened.
The fuel is too much. With idle rpm it quickly gets the plug dirty. With higher rpm the air/fuel ratio probably becomes less dramatically busted and the engine runs better.
We had a suspect : the fuel filter was changed 1 week ago. There was some dust in the bottom of the cup of the filter and the filter was grey.
Opening again today the filter, the thing was evident: a lot of powder in the bottom of the cup and the filter dirty.
Where is coming from all that powder? From the tank , of course. Infact we kept off the sender and we looked into the tank. The surface was covered by that dust.
All this despite a treatment with a layer on the internal surface of the tank.
The treatment did not involve the part of the surface under the cup that so remained rusty.
Before changing the injectors a Bardhal injectors cleaner was added in recent weeks and this has probably set in motion the rusty dust that was under the cup.
We have no other explanation considering that all metal and rubber hoses of the fuel lines are new.
Result: already ordered a new tank. I'm sick of this.
The pump will be cleaned and I hope to obtain , at last, an engine working fine.
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A Co meter is only partially useful. An analyser that measures CO and HC is much better. You can have perfect CO but high HC (anything above 500 is cause for concern but around 200 is great) will indicate poor combustion.
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A Co meter is only partially useful. An analyser that measures CO and HC is much better. You can have perfect CO but high HC (anything above 500 is cause for concern but around 200 is great) will indicate poor combustion.
Thank you Stick. I saw that this is a parameter present on the screen of the instrument used on my car.
But here we are to discuss again about fuel.
When you see , only one year ago , an environment like the one of the first picture, with a brillant and even elegant white :D, you can't imagine that only 12 months later all this can be transformed into a disaster like the one that you can see in the other pictures. Only when I saw the powder found in the filter's cup I surrended and I was compelled to think that all that nice white could have some problems. As a matter of fact ....
The coating is cracked and not adhering to the metal in many parts of the tank.
Probably the metal wasn't completely dry when the coating was positioned, because it seemed clean in the photographs that I saw one year ago.
The debris that you can see is only a fraction of the total and the last pic was made after a treatment with phosphoric acid just washed away a few minutes before.
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By the way: I ordered a new tank to MB and the delivery is scheduled for september 23 !!! (of this year :) ) . I suspended the order.
So I asked to Niemoeller and they will tell tomorrow a certain date of delivery (it will not be a date so close).
In the meantime we will treat the tank to get by while waiting.
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A few years ago I did have my tank dipped into an acid bath and I then used the Por-15 fuel tank sealing kit. So far so good!
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A few years ago I did have my tank dipped into an acid bath and I then used the Por-15 fuel tank sealing kit. So far so good!
Your tank met a serious person . My one , on the contrary , for 2 times, has met only stupid people.
Picture nr.1&2 = stupid nr.1 (Stones, sand and a perfect coating of the surface)
Picture nr.3 = stupid nr.2 (Fuel inlet of the 'tea pot' completely closed. The car worked only with 40 Lt. or more)
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When I needed to replace my fuel tank, the only dealer who was able to supply me with a new tank right away was Van Dijk:
http://www.classicsl.com/en/190sl-230sl-250sl-280sl-onderdelencatalogus/230sl-250sl-280sl-onderdelencatalogus/brandstof-onderdelen/
Give them a call if Niemoeller are unable to assist.
Good luck,
Mike
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Your tank met a serious person . My one , on the contrary , for 2 times, has met only stupid people.
Well, I kind of did it myself. I took the tank to people who dip stuff into acid. They kept it a few days. Then they usually coat everything in oil to avoid flash rust. In my case I requested them no to do that and call me immediately when the tank was out. I then just applied the POR-15 sealing as per instructions given in the kit. Quite easy and cheap to do. You should give it a try.
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You have to be very careful when having your tank adic dipped. I've seen where they came back spotless minus the flower pot. One of the pics above shows that very clearly, and, you can't replace it once it's gone. After the tank is acid dipped it has to be placed in a solution that will remove and neutralize all of that acid or you will have problems later down the road.
I won't coat fuel tanks. I've seen more ruined tanks than I've seen those that were helped. We boil them out in a mild caustic solution until they're clean. Junk ones get replaced with new or used tanks depending on what we have available.
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Would there be a demand for a replica tank in plastic(as used in modern cars)
Kind regards
John
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When I needed to replace my fuel tank, the only dealer who was able to supply me with a new tank right away was Van Dijk:
http://www.classicsl.com/en/190sl-230sl-250sl-280sl-onderdelencatalogus/230sl-250sl-280sl-onderdelencatalogus/brandstof-onderdelen/
Give them a call if Niemoeller are unable to assist.
Good luck,
Mike
Thank you , Mike.
Many, many thanks. I contacted them and they have the tank in stock.
Niemoller too was very precise and efficient, but they can deliver their tank in 3 weeks.
I'm in a hurry and so I ordered it in the Nederland.
I will let you know when it will arrive.
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Thank you , Mike.
Many, many thanks. I contacted them and they have the tank in stock.
Niemoller too was very precise and efficient, but they can deliver their tank in 3 weeks.
I'm in a hurry and so I ordered it in the Nederland.
I will let you know when it will arrive.
Excellent news Flavio! This was exactly my experience, Niemoeller were efficient but needed time & Van Dijk had the fuel tank in stock....
Best,
Mike
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Would there be a demand for a replica tank in plastic(as used in modern cars)
Kind regards
John
You might imagine that there could be, however, the mounting of the tank would need to be changed. Only three nuts hold the tank in place on our cars and somehow I can't imagine that working out very well with a plastic one. Some sort of reinforcement would be needed.
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You have to be very careful when having your tank adic dipped. I've seen where they came back spotless minus the flower pot. One of the pics above shows that very clearly, and, you can't replace it once it's gone. After the tank is acid dipped it has to be placed in a solution that will remove and neutralize all of that acid or you will have problems later down the road.
I won't coat fuel tanks. I've seen more ruined tanks than I've seen those that were helped. We boil them out in a mild caustic solution until they're clean. Junk ones get replaced with new or used tanks depending on what we have available.
Yes, Benz Dr. You are right. I have not yet posted the image of the pot. Here it is. One year ago it was not in bad conditions. Now it's destroyed. In that tank was poured only one can of Bardhal injector cleaner during the last year. I cannot believe that it can perform this effect . It's easyer to think to the effects of not neutralized acid . To neutralize the acid could be enough a simple solution of sodium bicarbonate (NaHCO3) with water.
By the way : I checked the photographs that the 'stupid nr.2' sent to me before performing the placement of the white cover. And curiosly the pattern of the detached cover that has been cut away in the 3381 pic here above, is similar to the one that you can see here (second pic ) .
Rust , acid , holes stopping : how many mistakes in a single tank....
A note: the new tank is arriving from NL , but if my one was the last pot available all over the world, it would have been possible to rebuild it ( with resin or , more easy, with inox 1 mm. thick). There is nothing that cannot be reproduced. And this is one of the simplest things to be reproduced.
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Hi guys. The new tank is still traveling... Nothing new to say about this...
But I wanted your opinion about this: we have seen in the previous messages that a plug ( the nr.3) goes quickly out of service with carbon deposits because the quantity of fuel in the cylinder nr.3 is too much.
I use this fantastic image of Joe Alexander ( thank you, Joe , for sharing, you are a great professor) to ask to you which could be the detail that remained open (it's probably dirty for the rusty powder of the tank).
Consider that the bracket moves freely and all the other plugs are remarkably lean.
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Hello Watson,
If just one cylinder is rich and fuel fowled, it could be the injector stuck open. Check the injector and try a new spark plug on #3.
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Hello Watson,
If just one cylinder is rich and fuel fowled, it could be the injector stuck open. Check the injector and try a new spark plug on #3.
Thank you, Joe, for your message. An honor . No, the problem does not come from the injector. As I told in the message#102 (I understand , it was a little long... ) the mechanic verified that the 5 cyl idle was coming from cyl #3; so a new sprark plug was tested on #3 and in a few seconds it became dirty. Then the injector 3 was swapped with the 6. The problem remained on the cylinder #3. It was not the injector. The problem comes from the pump that seems to deliver too much fuel.
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So guys , here we are ! The tank arrived from the Nederland and was installed. A little quantity of electric contact activator has been poured into the nr.3 exit of the injection pump ( into the part described as 'fitting' in the image of Joe Alexander, here above) .
The activator is enough to clean metal parts gently and it isn't too strong to damage metal parts.
A new fuel filter was installed and all the hoses of the circuit were washed with clean fuel (the old fuel had a strange grey shade; it will be good for my 11HP Simplicity to cut the grass).
With a 100 octane fuel (Shell V power is the only one here in Italy) the noise is now remarkably reduced. Some friends told me that this is the normal noise of the 230 and that if you want something a little quiter you must buy a 280.
The car has immediately changed behaviour. Now the engine has a good rithm, no uncertainties. Quite good.
The plastic of the 'tea pot' is white and quite different in comparison with the old one. The new tank seems to be treated with zinc and the fuel hose is in copper. The return hose seems to be in stainless steel. The choice of Zn + Cu is strange because these two metal could determine corrosion through a 'battery effect' (right word?).
Here some images of the details described above and the image of a strange jellow cream that is present on the exterior part of the pipe and seemed to be poured down into it.
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So I wanted to thank all the members that gave their opinion and helped me to solve the problem with all the messages that we exchanged.
The good thing of this discussion is that I have known a lot of nice people and I learned a lot of new things.
Thank you all again, guys, sincerely .
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Happy Motoring Watson!
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Good outcome.
It has been an interesting story watching it unfold and the twists and turns to finally work out the problem and have resolution. Have watched with interest.
Enjoy the ride.
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;D Hi guys. It's me again.
There is an appendix to my story and I want to share it with you , if something can be useful for someone else.
Well, my noisy engine was not exactly what I expected to have. If the mixture was lean, the noise was in some
way acceptable; but as it was necessary to enrich the mixture, the noise became stronger. So I found a friend
that was able to measure the compressione ratio with a reliable instrument.
The result is in the image that I attach : 11.75 was the value in two cylinders. we stop measuring. It was enough.
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Tired with my first technician I went to a new mechanic to 150 km away from my house.
He inspected the car and he listened to the whole story and looked at the pictures with great attention.
He was going to open the engine and then to tell me what could be done.
Some day after he called me and said that when he makes an engine he want to give warranty and to make this he was going to make again an overhaul, this time a complete one.
I don't show to you all the details with mistakes or defects he found.
I want to concentrate the attention to an aspect regarding the compression ratio.
We used a formula, universally accepted for the determination of the combustion chamber volume:
In normal conditions it's this :
volume of the chamber = single cylinder displacement/( compression ratio-1)
so VC = 384cc /(9,3-1) gives 46,26 cc of volume in a normal , untouched combustion chamber.
But we have seen that we had a compression ratio of 11,75 and so the volume is reduced to 35,7cc
About 10,5 cc missing ...
I didn't want to buy a new head from Mercedes or other sellers and so the solution was found with
special pistons built in Torino with proper excavations to obtain the missing volume.
I attach an image of the pistons.
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It sounds like you found the right mechanic. I am a mechanic by trade and that was a very strange problem to have. Happy motoring.
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Yess , Shvegel, it seems so . Thank you for the support.
I get to conclusion.
Before ordering the pistons we made a test to check if the reality was matching the theory ;).
The mechanic installed the valves with springs to obtain a good sealing.
Then he got some oil into a syringe and carefully filled what was remaining of the combustion chamber .
We were glad to verify that the quantity of cc was exactly 35.
This time the overhaul was really complete and the valve guides were the only details that were conserved .
They were new and in good conditions. Every other detail was changed.
The engine runs smooth and silent and when I look at the front of the car it seems to be smiling. :)
I hope all this can be useful .
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During this two years of troubles , I read , I investigate and so I found that , especially on cars coming from the United States,
very often were used these pistons. Probably the meaning of the particular shape is always the same.
We preferred the type of shape we used to have a good and uniform propagation of the flame front.
On the contrary the top of the two inclined surfaces seen in this picture could be an obstacle.
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Thanks for letting us know the final resolution, sorry you had to go through all that extra trouble (and no doubt expense). It reinforces the importance of selecting a rebuilder who truly has the expertise to do these engines properly.