Author Topic: 220SE Compression values  (Read 3527 times)

hansr433

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220SE Compression values
« on: July 18, 2020, 17:40:03 »
Still having woes with my freshly restored 220SE Cabrio.  It still has its original engine Type M127.V which was supposedly rebuilt 4,000km ago and dyno tuned.  If you have followed my other posts, then you know that on a recent 1500km trip I had sudden 2-3L oil loss which possibly sprayed out from the dipstick tube.  I have not found any leaks and since an oil change from semi-synthetic to mineral oil the car has behaved very well.  Starts and drives without issues and has not lost/burned any oil.  Also no smoke, but a slight burning oil smell.  We washed the engine and underside with steam and are keeping an eye on everything.

I have the Autopress Workshop manual and it lists compression values at 10-11 kg/sq cm for a high compression engine and 7.5-8.5 kg/sq cm for a low compression engine.  My car is an original US delivery.  Does someone know what type of motor I have?  I am attaching photos of the spark plugs and the print-out of the recent compression test on a warm engine.  The Autopress Workshop manual says to do the test with throttle wide open, which I did not.  Would this change values?  Can someone who has a similar engine and who has done a compression test comment on my values?

Plug 1 was slightly wet on the outside.  Plugs 2-6 looked similar.

Neat trick BTW to remove/install spark plugs without burning yourself.  The mechanic stuck a piece of flexible fuel tube onto the plug to thread the plugs and then tightened with a plug wrench.
« Last Edit: July 18, 2020, 20:42:23 by hansr433 »
Hans
1963 220SE Cabrio (Exterior: Navy MB 332, Top: Haarz Navy, Interior: 482P Sahara Beige)
1963 BMW R69S

PeterPortugal

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Re: 220SE Compression values
« Reply #1 on: July 18, 2020, 20:32:15 »
Hi Hans,

I believe they say do the test with throttle wide open to just speed up the process of getting the air into the cylinder. It doesn't affect the value, it's just faster to reach it.

That's my story anyway !

When I did mine I know I needed about 140 to 150psi and I was very surprised to get about 145psi on all cylinders !

That is equivalent to 10-11kg/cm2

Regards

Peter



1963 220se Cabrio
1968 280se Coupe

hansr433

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Re: 220SE Compression values
« Reply #2 on: July 18, 2020, 20:44:25 »
Thanks Peter.  I just noticed that 2 of the photos had not uploaded, so I fixed that.  My compression is much lower as you can see, so that's a problem.  Do you think that the engine have to be removed to fix this?
Hans
1963 220SE Cabrio (Exterior: Navy MB 332, Top: Haarz Navy, Interior: 482P Sahara Beige)
1963 BMW R69S

PeterPortugal

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Re: 220SE Compression values
« Reply #3 on: July 18, 2020, 21:01:39 »
Hi Hans,

You really need to find out if it is a low compression engine as your first port of call.

I am looking through my service manual. The values given are the same as you have quoted for normal and low compression versions but i cannot find anything to tell you how to identify which engine type you have.

I will keep trying.

Peter
1963 220se Cabrio
1968 280se Coupe

PeterPortugal

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Re: 220SE Compression values
« Reply #4 on: July 18, 2020, 21:05:25 »
Hans,

One thing to note. The service manual states that if the Max / min values vary by more than 1.5 you should carry out a cylinder leakage test.

Yours exceed 1.5 so even if you have a low compression engine you would still need further investigation.

Regards

Peter
1963 220se Cabrio
1968 280se Coupe

PeterPortugal

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Re: 220SE Compression values
« Reply #5 on: July 19, 2020, 08:29:20 »
Hi Hans,

After some research I believe a low compression engine has bigger combustion chambers achieved by a thicker cylinder head. The block is identical. I suggest you see if you can see a part number on your cylinder head. This might be a quick way to identify whether yours is a standard or low version.

If it is low compression version then some of your values are fine. The low values might be a problem that can be resolved by taking the cylinder head off only.

If its is a normal compression version then all your values are sub standard and it might be more serious and require the engine out.

I am sure somebody will provide some good advice over the coming day.

Regards

Peter
1963 220se Cabrio
1968 280se Coupe

PeterPortugal

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Re: 220SE Compression values
« Reply #6 on: July 21, 2020, 14:20:33 »
This subject Hans is exactly why I get frustrated with people complaining about putting W111 posts in the other categories.

it's a generic question, equally applicable to W113 probably, but most people have already screened it out and not even opened it.

You are left with no feedback.
1963 220se Cabrio
1968 280se Coupe

Benz Dr.

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Re: 220SE Compression values
« Reply #7 on: July 21, 2020, 15:11:53 »
This subject Hans is exactly why I get frustrated with people complaining about putting W111 posts in the other categories.

it's a generic question, equally applicable to W113 probably, but most people have already screened it out and not even opened it.

You are left with no feedback.

That's because no one really knows and not because of cross-contamination between 111 and 113's. Aside from the 220SEb engine, the drive trains are esentually the same on 250 and 280SE/SL. 

Uneven compression like this is usually due to leaking valves. Cylinders generally wear at about the same rate.  I would pull the head off and do a valve job. Good oppertunityto inspect the cylinders for wear.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

hansr433

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Re: 220SE Compression values
« Reply #8 on: July 21, 2020, 19:15:26 »
Peter and Dan, thank you for your thoughts and replies.

Dan, would badly adjusted valves not make some noise?  Can you listen to the engine in this video, and advise if you hear something amiss?  The video was taken just after the oil change and the engine was warm, not hot.  The oil was cold.

thanks

Link to video is here: https://www.dropbox.com/s/3q47ezoerx3nos6/MB220SE%20idling%20cold.mov?dl=0

Hans
1963 220SE Cabrio (Exterior: Navy MB 332, Top: Haarz Navy, Interior: 482P Sahara Beige)
1963 BMW R69S

Benz Dr.

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Re: 220SE Compression values
« Reply #9 on: July 21, 2020, 19:28:13 »
You can't hear a tight valve.  Valve adjustment rarely changes compression readings and once they start to leak they generally continue to do so.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

PeterPortugal

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Re: 220SE Compression values
« Reply #10 on: July 21, 2020, 22:39:58 »
Hans,

What Dan suggests is effectively what the cylinder leakage test would lead to.

Whatever the problems the head is coming off.

Maybe run the compression  test again just to be sure if you have not noticed any other issues?

Peter
1963 220se Cabrio
1968 280se Coupe

austinado16

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Re: 220SE Compression values
« Reply #11 on: August 02, 2020, 14:55:50 »
Hi Hans,
Compression tests are done with a warm engine, wide open throttle, all spark plugs removed, coil wire grounded, and then crank the engine until the compression test gauge stops rising.  At that point, you have reached the maximum amount of air pressure that the engine will hold.

Converting your bar numbers to psi, you only have 117psi in Cylinder No.3.  You also have significant oil consumption (on your long trip).  I doubt very much that you lost 3L (3qts) of engine oil out the dipstick.  That much oil would have made a tremendous mess in the engine compartment, likely made it onto the exhaust pipes, smoked like crazy, and you certainly would have smelled it inside the car, and had it sprayed all over the underside of the car, and on the back of the trunk and tail light area.

My suggestion would be to purchase your own compression test gauge.  They are about $30US here in US.  Repeat the test and write down your numbers.  Any cylinder with less than 125psi/8.5bar should be retested, with what's called; a wet test.  During the wet test, you will squirt/pour a few ounces of engine oil into the cylinder.  Then immediately repeat your compression test......again, wide open throttle, all spark plugs removed, and crank until the gauge stops moving.  The purpose of the wet test is to prove if you have valves that are leaking, or compression rings (on the piston) that are leaking.  The engine oil will temporarily seal the piston's compression rings, but it cannot seal the valve seats.  So if the wet test gives you a higher reading than the dry test, you know the compression rings, and/or cylinder is the issue (worn out rings, broken rings, rings that are stuck to the piston via carbon deposits or damage, or a deep scratch in the cylinder wall, or a cylinder that is simply worn out at the top of the bore).  If your test result remains unchanged, you know you have a valve seat/valve sealing issue (valves not closing completely due to too tight of a valve adjustment, burned exhaust valve, valve seat damage/wear, bent valve stem).  Doing the wet and dry compression test, IMO, is all the testing you need to do.  Sure, you can do a leak down, but why?  If you have a valve issue, the head's coming off and getting rebuilt (unless you find a tight valve adjustment) and if you find a ring issue, the engine is coming apart.

Some additional info:  Oil consumption happens 2 ways;  1)  The valve stem seals fail, and the engine begins sucking oil down the valve stems, yes, both stems (actual suction on the intake valves, and a venturi type effect on the exhaust valve stems as the high speed exhaust gasses pass over the end of the valve guide).   An engine can consume  a lot of oil down the valve guides.  Common indicators of valve seal failure are blue smoking at initial start up, especially after sitting over night, or for a few days or weeks, smoking on acceleration from a long traffic light, and smoking upon initial acceleration after coming down a long hill.    2)  The oil control rings.  Remember, compression rings DO NOT control oil getting up up the cylinder and into the combustion chamber.  So you can have a good compression reading (a compression test ONLY tests the compression rings and valve seats and head gasket fire ring) and still have an engine that consumes oil.  So you can have oil rings that are broken, worn out, have lost their spring tension (so they don't push out against the cylinder wall firmly enough to scrape oil), or are stuck in the piston due to a build up of carbon and goopy oil.  Symptoms of failed oil control rings are an engine that smokes badly under acceleration, especially hard acceleration.

So if I was working on your car, I would redo the dry test, then do a wet test, and depending on what I found, make a decision as to what step I'd take next.  Good luck!

hansr433

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Re: 220SE Compression values
« Reply #12 on: August 02, 2020, 20:06:44 »
Hello Todd,  thank you for your comprehensive reply.  There is a lot of good information there.

I had checked oil levels prior to setting off from London, and all was well.  I was keeping up with traffic on French autoroutes  where the speed limit is 120km/h.  About 200km into the trip I noticed lots of oil dripping along the length of car during a gas stop.  The engine compartment was filthy with oil droplets, as was the undercarriage all the way to the rear bumper.  I re-filled the oil and continued the trip at a slower speed, checking every 30-40 minutes.  I did not lose or use any significant amount of oil for the rest of the trip.  Once I arrived here in Tuscany, I had the oil/filter changed and the engine compartment and undercarriage steam cleaned in order to find the source of the leak.  Of course, nothing is leaking now.

So, next step is to repeat the compression test as you have suggested and take it from there.  BTW, the car is currently immobile with a buggered front axle stub.  When it rains, it pours.
Hans
1963 220SE Cabrio (Exterior: Navy MB 332, Top: Haarz Navy, Interior: 482P Sahara Beige)
1963 BMW R69S

austinado16

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Re: 220SE Compression values
« Reply #13 on: August 02, 2020, 22:51:14 »
What you probably experienced is the blow by from cylinder's 2 and 3, which are both low in compression, and likely due to either failed compression rings (in some way), or, since you have 2 adjacent cylinders with low compression, you could have a failed head gasket fire ring, between the 2 cylinders.  So yes, repeat the compression test, both wet and dry, and then for this situation, I'd recommend a leak-down test on just those 2 cylinders, and while pressurizing one, listen and feel for air hissing out of the spark plug hole for the other (indicating a failed head gasket fire ring between the 2.  Remember when you do a leak down, you have to have the cylinder you're testing, at TDC for that cylinder, so that both valves are closed.  That will mean that the other cylinder will have a valves open.  But you still may be able to feel or hear air moving out of the other cylinder.  The way to get around having the valve(s) in the other cylinder open, would be to remove the valve cover, loosen the valve adjustment, and remove the rocker arm(s) for the other cylinder.

Also, make sure that your crankcase breather system is open from the valve cover, all the way to the throttle body.  A blockage in the breather system will cause the engine to blow oil out of the dipstick