Main.TrailIndexPage | Engine | Overhauling Ė things to know

Rebuilding and Overhauling

This section is part of the Engine section.

The following is the content from the old Yahoo documents on the site. It needs to be structured and edited in the correct sections of the entire document. After moving particular content to its correct place in the manual, please delete it here.

Engine Differences

There are a lot of variations between the 3 different engines. Early 230SL pistons used 4 rings and 24mm pins, intermediate used 3 rings and 24mm pins and 3rd version used 3 rings and 25mm pins. I think the early version used a drilled conecting rod similar to the 220SE of which the engine was designed from. The 230SL used 3 different pistons while the 250SL used a similar piston as the 3rd version 230SL but it didn't have the long skirt like a 230SL. Like most us, I prefer a short skirt...

The 230SL and 250SL have the same bore but the 250SL has a longer stroke. The piston is also a 3 ring type and has a 25mm pin. The heads and head gaskets are interchangable on the 230 and 250.

The 280SL uses a 3 ring piston with a 25mm pin. There were two engines made which are quite different in design and the head gaskets are totally different. You can't mix them up. The conecting rods in a 280SL are quite short and have a small hole drilled into the upper side of where the bearing fits. Every time the journal in the crankshaft passes this small hole a shot of oil sprays out which hits the bottom of the piston to help keep it cool and to oil the pin bushing.

The 280SL is the cutting edge of what the factory could do with this engine. Everything is stresed higher and further than ever before and even all the torque values are much higher. Angle of rotation is the norm rather than straight torque values and the use of stretch bolts is used. Conecting rod bolts are started at a set torque and then 90 degrees after that. You would think they would snap off but they never do. Same for the flywheel bolts. Overheating is a problem with some 280's and seems to be a bit worse with the late US model. This could have something to do with the distributor timing used but a lot of this problem relates to the size of the cylinders relative to the block dimensions. AC in these cars can really overheat the engine due to the confined engine bay space. This didn't seem to be as large of a problem in the sedans of the same era due to the extra room under the hood on those cars.

As for the 250 being a weak engine prone to self destruct, I think that's nonsense. I've seen good and bad examples in all 3 engines. Oddly, only the 280 seems to have suffered from heavy camshaft wear in the examples I've seen. I've seen more engines with death rattle pistons in the 230 and 250 line but I think they were from older and higher mileage engines. They are older so it stands to reason from that perspective.

The 280SL had several designs that made it somewhat better. External oil cooler, larger oil galleys, cooled pistons, visco fan clutch, better ignition system, two oil pressure relief valves and yet they still shared a number of parts from the 250 engine. The heaviest wear areas I see are cyinder walls and valve guides in all engines. If the cylinder walls are really worn then the crank bearings will be too. Heavy blow by into the oil pan usually dilutes the oil with gas and other contaminates and the bearings suffer from this. Proper maintenance is the only way to prevent or slow this from happening. Given the low miles these cars are now driven every year that should never be an issue any more. Dan Caron

Actually, I did some experimenting with this switch years ago. However the passages in the crankshaft, bearings and connecting rods are different. The cranshafts are different in other ways also. You would have to replace the crankshaft and the connecting rods as a unit using the correct bearings.

My experience has never shown me that there was a real weakness in the 250 enine. I do believe that when Mercedes designs a new engine, that they try to "improve" and incorporate latest design features in the newer engine. So as far as being "defective or weak", I probably do not agree. As far as latter engines being improved, possibly!

I know lots of high mileage 250SLs. The secret to longevity is good maintenance, and good storage. The earlier engines 230, 250 were a lot more foregiving as far as oveheating...more space between cylinders. However any of the engines can be ruined from severely overheating.

Joe Alexander


(On wanting to remove the engine to fix a broken timing chain). I have never had to do work like that and I hope I never do. Just to educate myself, why does the engine need to be removed from the car? Aren't you working down from the top? I guess if you think replacement of pistons and rods are in order, then engine removal would be necessary. If you're just doing top end work like valves and stuff can't you leave the engine in?

Will Samples says: Breaking the timing chain is another subject entirely. These cars are not known for breaking timing chains. In 20+ years of working on them yours may be only the 2nd or 3rd I have heard of. If you want any advice, give us more information on the situation.

Will, Thanks for the manifold separation information. I may not need to do it anymore. I pulled the head off today and was able to look at the lower timing chain sprockets. Not bad. I was also able to pull the timing chain out of the engine. It broke at the master link. I am now wondering if the link was installed properly. The cylinders look good and the one I checked for round and top versus bottom was within specs. I am thinking that I should do the valves, put on a new cam, and put it back together. The engine was running good before the chain broke. Are there other things I should check before going with this option.

Will says: I am still surprised to hear the chain broke at the master link. Never heard of this. After the chain broke I have to assume the engine momentum carried it thru a partial revolution. If this is the case a piston had to come in contact with a valve. Pull the head apart and have the valves checked for being bent. And naturally, do a valve job as needed. It will be interesting to see how you thread the new chain back in. Please tell me how you do it. Or maybe you have the engine in pieces. In that case, no problem. You mention changing the cam. What is its story? Broken, then replace. If not, then it can be salvaged if you wish. What else you do to the engine depends on how apart it is, your abilities and level of interest in rebuilding.

The camshaft and one of the camshaft bearings was broken when the timing chain broke. I know where there is a 1964 220 SE parts car. My question is, is the 220se camshaft the same as the camshaft in my 230 SL? I have been told that the blocks of the two cars are the same. The 230 is bored slightly larger. Is that true? I have the engine stripped down and ready to be removed from the car with the exception of the transmission. The factory manual advises removing the transmission with the car. My mechanic friend suggested I uncouple the transmission from the engine and remove only the engine. Has anybody removed an engine? What worked best for you?

I have just rebuilt a 1969 engine. The timing was all set while the engine was on the stand. So I'm sure that is correct. I'm getting a good spark. The fuel pump may have been stuck at first but now I get fuel all the way to the injectors. How can I check to se if the injectors are spraying? Another note is that the engine is trying to start. So I pulled the plugs. #4 has blck soot and #5 is a little tan. I think these two are where the "bump" comes from as you can tell the engine is trying to start.

This may be basic and stupid but are you sure the distrutor is not out 180 degrees. Happens a lot.

Will Samples says: Not only do the injectors have to spray a correct pattern they have to spray it at the correct pressure. The point at which they pop off. The only way I know to do it is to use a fuel injector tester. It is a hand pump that uses a fluid like mineral spirits, has a pressure gauge, and allows you to see the pattern and pressure as the injector sprays. Since most of us do not have this $600 tester you need to send the injectors to a shop to be tested. Most diesel pump rebuilders can do this. A quick test to see if the no-start is fuel related, is to spray a little starting fluid into the intake. Open the butterfly, give a quick spray, close the butterfly, crank the engine. If it sounds like it is hitting on all 6 then you have a fuel delivery problem. Remember, injection pump timing is critical, called "stabbing the pump", and is done as per shop manual. If #4 plug has soot, it may indicate an injector not spraying right.

My 1964 euro 230 SL was using oil. Blue smoke on morning start up, but no smoke thereafter. After start up and though a drive there would be no further smoke, even when you revved the engine. I put it in the shop and they determined that the valve seals and valve seats were shot. The valve guides were quite loose. The head was rebuilt, complete with new valve guides. It was started today and it is really blowing blue smoke, just rev the engine and it blows and blows. Any ideas as to the problem? A wet and dry compression check was done before the work and it was great. We pulled a spark plug-black soot. The intake manifold had one odd thing. On the passenger side on the intake manifold towards the front there is a rubber tube from the air cleaner to the intake manifold. The manifold fixture that the tube mounts on is supposed to have a screw in it with which to adjust the idle. The screw was missing and was probably missing for years. Without the screw there is a hole so before the rebuild the engine must have been able to suck air through the screw hole. We had installed a screw. We do not see how this could have any thing to do with the smoke, but I mention it because it was an odd deal and something that was changed.

Will Samples says: Sorry to hear after all the work the smoke problem. As you can imagine, long distance diagnosis is hard. But I will give you my best shot. The valve job brought the head back into spec so that the valves are now sealing properly. Prior to the work the valves were not working at full efficiency. The properly sealing valves have acted to increase the pressures inside the combustion chamber. The increased pressure is putting more pressure on weak piston rings. The weak piston rings (or worn out rings or worn cylinder walls) were a pre-existing conditon. A compression check would not necessarily point this out. A cylinder leakage check would have been a good idea. I cannot explain why, but you can have good compression with rings that allow oil to pass thru the engine. I had a 280 SL that was a great driver, engine started on first crank, ran very well, etc. But it smoked so badly that I had people yelling at me to get off the road. A quick solution is to use synthetic oil. It will not burn as visibly as regular oil. Long term solution is new rings. I am stunned that the car ran very well without the idle air adjusting screw. There should have been a loud rush of air at that point such as to alert one of a problem. I agree, it will not affect the smoke issue. Another remote possibility is on cars with automatic transmissions, the vacuum operated modulator on the trans will develop a leak and allow trans fluid to be pulled into the intake and burned. Again, giving a nice smoke cloud. The valve job could have accelerated the deterioration of the modulator. Again, it gets back to the increased efficiency of the engine with fresh valves. I do not believe it could be the brake booster or master cylinder, but it is easy to check by pulling the vacuum line to the booster and blocking the port at the rear of the intake, then running the engine.

Thanks for the help. She fired up tonight. The problem was the last place I looked. I had put the engine back together by the "book". Therefore I was pretty sure everything was correct. What I didn't do was check the other guys work. The shop that rebuilt the head did not set the valve clearances. After a long day and the purchase of a 17MM crowfoot wrench, I got them adjusted. She fired right up and purrs like a kitten.

Will says: good to hear you got the 280 SL running. The people doing the valve job should have pre-adjusted the valves for you. It is part of the valve job for overhead cam heads. Once the head is torqued in place on the block it is a good idea to recheck the valve adjustments. Now, after running it for a few miles or 1 hour or so, recheck torque and valve clearances and not a bad idea to change the oil as well.

Does anyone know what a fair price range is for a complete 280 SL engine rebuild (cylinders/crankshaft/valves). The fuel injection was recently rebuilt so it's fine. I'm awaiting a quote from my mechanic, and I'd like to be prepared beforehand, as I have no idea what is fair. I know it won't be cheap!

I just had mine done completely (including the injection pump) and it cost about $ 8,200. Be prepared for "little things" that are uncovered during the process. Make sure that a skilled 280 SL mechanic does the work. While you're at it, check/replace the clutch plate and thrust bearing (if they are old). Have them do a compression and leak-down test before the overhaul and repeat afterwards to compare the results.

Will: You will need some time for the rings to seat on the engine rebuild before you do the compression test and cylinder leakage test.

On short vs. long block: a "shortblock" is just the engine block itself, ie: no head. A "rebuilt engine" would be a complete unit, with at least a "head" on it. The long block includes the head and valves while the shortblock does not.

Dan says: an engine rebuild should have: block degreased and cleaned head cleaned block bored new pistons block decked (if needed) crank turned rods sized new rods bolts and nuts if needed new rod bushings main and rod bearings timing chain and rails new crank gear intermediate drive bushings (if needed) head planed R&R valve guides grind valve seats grind valves or new ones if needed new valve springs All valves hand lapped and vacuum tested all cylinders vacuum tested and then the whole system cylinder tested new rockers if needed valve stem seals all new gaskets new oil pump chain tensioner clean and test cold start valve clean and test fuel injectors grind flywheel if needed new pilot shaft bearing injection pump is a seperate issue Old books give about 45 hours to R&R the engine and rebuild it which really isn't enough time for cars this old. Around 7 to 8,000.00 CDN depending on what's needed.

The cost of having the crank reground is not that much and is a job you should have done while it is out. Main cost in doing these is disassembling the engine. It is especially critical to do this if you plan on using a set of new bearings. At a minimum the crank should be polished.

I agree about polishing the crank at a minimum. A couple other things to do at this time are to crack-check (Magnaflux or similar process) the crank and rods, and balance everything. These might be standard procedures at your shop, but best to make sure they do them. All the little things you should do while the engine is apart add up, but now is the time to do them, and you'll be glad you did it right.

I need some advice. I just had my 1969 280SL engine overhauled by a Mercedes professional. It runs great, but there's a problem. When cold, the engine exhibits no problems. When hot, it still runs perfectly, but cylinders 2 and 3 start burning oil. I thought it could be valve guides or seals, but both are new. My mechanic thinks it's a crack in the head. There is no blow-by and compression and leak down tests are well within the range of a new engine.

Chuck Gale: I agree with your mechanic. It's probably a cracked head or faulty head gasket. Jump on it now and fix it before it leads to other problems.

Joe Alexander though: Cracked Mercedes cylinder heads in these models are very, very rare. And even if so, it is almost impossible to cause the problem described. Cracks will usually cause some kind of cooling system or combustion chamber contamination problem other than what you have described. Compression pressure in the combustion chambers exceeds the engine oil pressure and will force oil away from the combustion chambers if their is a crack. So you would have excessive blowby or contamination in the oil or coolant(radiator). My thoughts are; if the intake ball stud bases are loose or not sealed oil can leak from inside the valve cover around the threads of the ball stud bases and into the intake ports of the head and get sucked into the combustion chamber thus oiling up those plugs. That's if your lucky. Just remove the ball stud adjuster bases on those cylinders reseal and torque back in place. A more likely possibility is something was overlooked, did not stay put or broke during rebuild or break-in. Here are the most likely causes for oil in the combustion chamber; defective or loose intake valve guides or valve seals in the cylinder head, defective or broken piston ring, or a piston or cylinder problem. If your engine is using oil and it is NOT ending up on the spark plugs (crusty deposit), then your exhaust valve seals or guides are loose or worn. The oil passes through the exhaust guides and into the exhaust port of the cylinder head and out the exhaust without ever entering the combustion chamber. Finally there is always the slim chance that something highly unusual may be the problem. My advice is start with the cheap things first; remove the valve cover and check to see if the intake valve seals and guides over those problem cylinders have stayed put. Check and re-seal the intake ball- stud bases over those cylinders. Review your rebuild invoice to see what parts were replaced in the head and the bottom end. This may shed more light on the problem.

I need new pistons for my 230SL, 1 mm oversized (that is, 82.5 mm). According to the data card, the car was first delivered on 3/11/65, and it still has the original engine. The only source I have heard of so far is Mercedes itself in Germany, for some $215 each. Any suggestions for a quicker or cheaper supplier? (I am in southern Calif.).

An option is Deves, and I think they have a website.

Will says: there are two styles, depending on motor number. Main dif is wrist pin diameter of either 24 or 25mm. Unless someone has the pistons just sitting on their shelf at home, you may be forced to use MB pistons. If they are complete with wrist pins and rings, then the price is not too bad. Current MB list for 250SL pistons is $8000.

I needed a set of 2nd oversize 230 sl pistons. After looking everwhere with no success, I went to the local MB dealer and was able to purchase them for $215 each ($Canadian) including pin and rings.

Group: I currently use Mobil 1 (10w 30). I have read that one should avoid synthetic oil during the break in period of a new engine to allow the valve seats to settle and to avoid "flat spots" on the cam. Don't know what that is, but it sounds bad. I did nothing to the valves (other than adjust the clearance), but can anyone confirm the proper oil to use during break in for the new cam and rockers?

I was told by Gernold (SL Tech) to avoid any synthetic (I believe there might be an exception for absolutely brand new engines) I was thinking about switching to it because my 2002 ML320 and E320 use it and thought it might be convienent to have just one type. Per his advice, I had my oil changed recently (had put on a whopping 500 miles) and stuck with standard 15-30. This does not really answer your question, but you might give Gernold a call and ask him for more detail.

I have marginally ok compression except in the cylinder with a valve guide that moves. The main symptom from the guide is smoke, most of the time, when at idle and startup. When the last valve adjust was done I have the smoking looked into and the problem was detected. The shop tried epoxing the guide in place which was warranted for lifetime or one revolution of the crank which ever comes first. It worked for about 1000 miles. 999 miles longer than I expected. So now I am considering the suggested valve job. How much more work =$ is it to fix the bad compression. Does compression problems come from rings or valve or both? Resleeving cylinders?

Dan Caron says: if you do the top end will the bearings fly out of the bottom? I'd pull the engine and look at the bearings. If they show signs of wear then I'd do the whole engine. 230SL's seem to have a habit of swallowing valve guides and snapping off front crankshaft ends. Some of them are nearly 40 years old now so I suppose it's not out of the range of possibilities.

Joe Alexander: if the head has to come off recondition the entire head and change the timing chain. The exhaust valve guides usually wear more quickly than the intake. When a guide comes loose in the head it no longer guides the valve into a nice tight seat. So compression is lost. Worse is the fact that by moving up and down in the head it slowly enlarges the hole it was once pressed into. Now an original standard size valve guide can not be used. An oversize guide must be ordered and the hole will need to be trued-up and the new oversized guide pressed in. The longer the guide is loose the more damage occurs to the head. Eventually the valve seat will be ruined and the entire valve may come loose and drop into the cylinder with catastrophic results. A complete valve job will usually solve compression and oil usage problems 95% of the time. I would usually not recommend going further unless obvious problems are apparent. First, if your car has factory AC the job will require four or five hours more labor. The AC bracket on these models is a major pain to remove. I have the factory published time guides for this model. To remove and replace the cylinder head the book shows 7.5 hours, add 4.1 for AC! Now add the machine work and any additional operations to be performed. As far as parts, recondition the entire cylinder head figure on one headgasket kit, six exhaust valve guides, six intake valve guides, a set of twelve valve seals, at least one valve, and hope that the rocker arms, adjusters and cam are ok. Your engine should be re-torqued and valves adjusted after warm up and again at 500 miles. Change the oil during the procedure also and change the timing chain if it is the original. So add time and parts here also. Most shops do not go by the book anymore on flat rate for these old cars. Too many unexpected surprises and unexperienced hands. In short depending on rate, skill and speed of the technician working on the car, the price will vary. In addition, machine shop prices for reconditioning the head will also vary widely. My advice, get some estimates and it may be worth traveling to get it done correctly and economically!

Dan Caron - oil will be pulled into the engine through the intake valve guides. I did an engine a few years back and it had a completely new bottom end. The head was used but everything was redone. This engine smoked right from the first time I started it. I've done many before and after and none of them smoked. What I found was pretty interesting. The valves and seats were heavily worn and so the valve springs weren't able to apply enough pressure on the sealing surface of the valve. This caused them to leak and also to pull oil down through the seals. The seals only prevent oil from running down the valve stems and can't stop it from being pulled through under vacuum. You can tell how much wear is at the valve and seat by using a depth micrometer and then subtracting the difference if the head has been planed. Anything more than .010'' and I use a piece of valve spring shim stock under the roto cap. I also use all new valve springs and valves if required. By using a new valve you can easily determine how deep the valve seat has been cut. The workshop manual has all the specs which should be followed pretty closely.

Naj: the BBB says to use some loctite product (sorry details not to hand) to re-install the crank balance weight after replacing the oil seal. What do the experts use??

Bernt Damm: As far as I know, you put the weight in place and pull it on with the bolt. At the same time, you have to make sure that the 2 key pins go where they should. This can be difficult. When the weight is on and the keys are in, you torque the bolt and that is it. The loctite solution is used only in cases where the actual weight is not a tight fit onto the crank anymore. It you can't push it on by hand and had to pull it off with a puller, then you don't need loctite or anything.

Dan Caron: I don't care what the BBB says ( what does that stand for anyway) if you break that screw off trying to remove it , you're screwed - and that's what will possibly happen if you do. This screw is torqued down to 130 ft lbs and it won't back out if it's installed properly. In fact I use a small amount of oil on the treads to help in the process. I don't use locktight on anything that old. Period.

Nathan Keith: Here is my 2Ę worth. I am probably going to raise some hackles here. I am just the opposite. If the shop did not use Loctite, then I pull the car from the shop and have someone else do the work. If you research as to the purpose of Loctite and other thread sealants; not only do they fill in the gaps between the threads thus producing a stronger mechanical bond, but they also prevent the metal to metal bonding that come with even slightly dissimilar metals making it easier to remove a screw, bolt or nut. I for one, do not put any threaded product back together without either Loctite or a copper thread seal. Others have scoffed at me over the last 40 years but I have never (and that is a long time) had a breakage or difficulty in disassembly on any parts I have put together with Loctite or thread seal. I would not even think of putting together the bottom end of an engine with out Loctite (I guess if I still had the wired castle nuts, like on my MG TD, I might not use sealant, but a wire would have to break for the crank and rods to come apart). If you don't want parts to vibrate apart, and you want to be able to take them apart with ease then use a thread seal.

Naj: BBB is the 'Big Blue Book', the repair manual written for American Dealers. The loctite is meant to go on the crank journal where the balance weight pushes onto. As Brent Damm suggested if the weight pushes on by hand then this treatment would be required. Luckily, mine had to be pulled out with a hydraulic puller so it will go back in - no loctite. The main bolt also had THREE large spring washers (also mentioned in the book). This was a mod done somewhere along the line - maybe to cure broken front stub on the crank?

Dan Caron again: Let me clear this up a bit. I had two engines come in for rebuilding. Both at the same time. One was just your garden variety wornout '64 model. The other a bit more fresh. The '64 had never been apart from what I could tell. The somewhat newer engine had been. So, the old one came apart with only a few small oil pan screws breaking - about what's expected. The newer one was an absolute bear to get apart. Crank pulley bolt was broken by PO and that was why it came in. Crank had to be pulled and several screws had to be drilled out at the machine shop including 3 head bolt screws. These had to be carefully ground off at the top of two of them and the third one broke off in the block - also by PO. This was the only way to get the head off. Anyone care to take a guess as to why all this happened? I use nickel anti-seize and copper silicone sealer - once in a while Teflon in a tube. Head bolts should be lightly oiled. BBB doesn't say much about this really.

And Joe Alexander: The front crankshaft area is an area of extreme stress. You have the crankshaft chain sprocket, the main belt pulley, and the vibration dampner with counterweight all working on the end of the crankshaft. Loads from all the engine accessories such as the alternator, waterpump, power steering and air conditioning concentrate force on this area. Some early engines experienced failures at the front crankshaft/vibration dampner connection. The early 113 engines had three bolts holding the vibration dampner and pulleys in place along with the large main center bolt. Later engines used six bolts and the new high-tech "Stretch Bolt" to hold everything together. If the assembly worked its way loose, the movement and resulting wear could ruin a very expensive crankshaft assembly. Some VERY minor wear or looseness on the crankshaft end can be dealt with by using something like Locktite Stud and Bearing Mount during re-assembly. The crankshaft woodruff key which holds the timing chain sprocket in place should also be checked for wear or looseness during major repairs. The crankshaft chain sprocket itself should be automatically replaced during major engine repairs or after timing chain failure. Correct torque on the front crankshaft bolt is critical to prevent loosening and possible damage. The later engines using the stretch bolt used a torque setting along with a 90 to 100 degree angle of rotation after the intitial torque setting was met. Now some technicians will use a sealer between the crankshaft end and metal seal ring to prevent any oil from sneaking around the front main seal. As far as locktite and thread sealer: if the bolt end terminates in a coolant or oil gallery I use sealer to prevent leaks. As far as thread locking compounds, pay careful attention during dissassembly to see where the factory used such compounds. My 190-SL factory shop manual suggested using graphite oil as a thread lubricant for head bolt threads and bearing surfaces during assembly. Whatever works for you. There are probably many good solutions. Some very tough-to-remove bolts can be pre-loosened by smacking them with a hammer first, (impact will loosen rust or thread locking compounds). As mentioned heat is always an option.

Dan Caron again: now we are getting to something. The early cranks are as you describe them but the crank bolt is a stretch screw I believe. It doesn't have the heavy cupped washers behind it though - just this thick washer. I still think it's not a really good idea to use thread locker in this area. If it's loose or worn the damage is already there and may need to be built up or replacement parts needed. Good idea about the new crank gear and other related parts. Crank gears take a pounding and receive more wear than almost any other part in the chain system. I've had more bad luck than good with impact wrenches. I remove everything by hand or use heat especially on screws stuck in aluminum housings. My approach is more in making sure that whatever I put together will come back apart in the future but not break in that process. If a screw comes loose it usually damages the thread. How much damage will determine the repair or replacement. 230SL's are prone to crank-end problems as I've stated in earlier posts, so I'm fully aware of this and agree that they pose a special challenge to the rebuilder. One reason I recommend staying away from AC on these cars.

Sanding off the bearing journal on a mercedes to make the clearance less Ė Ouch!

Dan Caron: I do it all the time. But not on the separating surface. In this case I'm talking about the main bearing that is used to locate the end play. It's accepted practice that you carefully file the bearing shell on each side until it fits rather than grind a perfect crankshaft to a wider size. I've never had a failure doing this. Of course I'd rather have shells that fit but a re ground crank won't always fit this one bearing. I would never under any circumstances file the shell itself. That would be a very bad idea.

Joe Alexander: Yes, I agree Dan. At times, I also finish the thrust surface on the thrust bearing instead of cutting the crank. Some of the early engine manuals describe this process. I use wet/dry sandpaper on a perfectly flat glass plate instead of a file. The end results are the same, to control fore and aft movement of the crankshaft to approx .004".

I took out my 280Sl yesterday and after about a mile or so I noticed a rattling sound from the engine. I played around a little just to check it out and noticed that it got a little louder as revs increased. I suspected the beginning of a bearing failure and so I checked the oil pressure gauge which was hidden behind the dash opening for some paint work on the dash. The oil pressure showed zero! I carefully drove back home and drained the oil. I had been one quart exactly below the minimum mark. That's two quarts below maximum level. In my opinion and experience that is not enough to do damage to the engine so I am looking for another possible cause. The oil appears to be clean. There was one pin head sized metal chunk in the drain plug. It looked like aluminum or worse lead? No brass or copper. The filter appears good too. Is there any other possible cause for zero oil pressure reading, like an obstruction (either at the gage, or possibly in the oil circuit) or is there some part that can suddenly fail or come off in the pump without a sound or any other indication? I'm hoping there is! I also checked the picture on page 18-3/1 of the BBB. It appears as though I have none of the seals part no. 6 surrounding the holding screw 1. There are no remnants of seals either so I'm assuming they haven't been there for a long time. They are not parts of the oil filter kit either, nor is part no. 10 which seems like a hard metal seal or no. 13. Have the designs of these seals or filters ever changed or should all these parts be replaced regularly? I still do not feel that this find brings me any closer to my solution seeing as this is a condition that has been existing for a long time and my oil pressure went from a very healthy engine to zero from one day to the next.

You could have a pressure relief valve stuck open. That's just one of several choices, but a good place to start.

You said you had the oil pressure gauge behind the dash, was the oil line to the gauge tight, I'd check for oil in the interior, Also remove and inspect the oil filter for junk.

I disconnected the gauge to check and there is actually no oil volume coming out of the fitting. It should come pouring out. I also disassembled the pressure relief valve and found no meaningful obstructions. Due to the total lack of oil pressure I'm beginning to suspect a complete failure or disconnect to the oil pump. Could that happen without hearing any noises or other indications. Do the Engine experts (Joe, Dan) have any ideas?). I'm thinking now that the complete lack of oil pressure may be due to a problem with the oil pump. Since the pump is driven by the timing chain I don't think that's the problem because the camshaft turns. Is it possible that maybe the pickup for he oil pump could fall off. Does anyone know what might fail on the oil pump before I take off the oil pan.

The oil pump is driven by the same shaft that runs the tachometer. Does the tach cable turn? While it is rare, the skew gear that runs this shaft can wear out.

Is there an easy way to check if my oil pump is delivering oil, such as unscrewing the relief valve located, I believe at the front of the engine. Or can I simply unbolt a plug, valve or line at the oil filter housing so that I know whether it is time to remove the pump or not?

Dan Caron: If you see oil coming out what will that prove? That it pumps oil? That's not all that conclusive and it may not be any good. If you have serious concerns about your oil pump you should replace it.Engines don't just loose oil pressure all at once unless something big happens. Maybe the helical drive gear let go or something like that. If it shows little or no oil pressure at the gauge that's not good. Driving a car that short distance home or to the gas station can be ruinous. It may be too late to avoid a rebuild I'm afraid. Hope it turns out OK. Also, I once saw an oil pump screen filled with pieces of timing chain - the black hard rubber stuff. Completely shut off the oil flow. Can you see if any chain rails are damaged? I'd pull the pan and see what's going on. Could also be a failed oil pressure relief valve on the bottom of the pump.

Joe Alexander: hello Tom, Dan has a good point. Check to see if the tachometer is still working. There is an aluminum/bronze bushing which holds the timing gear in place that drives the oil pump and tachometer. Your tachometer attaches to the cap on this bushing. If this bushing wears enough the timing gear can move upward and dis-engage the oil pump! The engine will continue to run but the oil pump will not. The tach, may or may not continue to function. The drive gear and bushing removal is a little tricky. You may want to remove the steel oil sub pan to look at the situation at the oil pump first. You will need as 5mm allen wrench. A long 5mm allen/socket or a 5mm "T" handle allen will work nicely. The sub pan can be removed fairly easily and the oil pum can be inspected. If the pump looks ok I would check the drive gear and bushing next. I have one of these engines on a stand 30 feet from this computer.

Hi Joe - you were, of course right. Do you have a spare oil pump drive shaft for a late 280Sl engine? Mine was completely bent apart where the fork should clasp the top of the oil pump drive. For that matter does anyone have the spare part?

It looks like I may have to take off the cylinder head because the bushing that holds the shaft for the oil pump and the tachometer drive just barely interferes with the head. Somebody please tell me that I don't have to open a (hopefully still) sound engine in order to remove this shaft. No, MB wouldn't do that, would they? Can anybody please tell me that I'm wrong?

Joe Alexander: as I recall, the bushing will clear the head, even though it looks like it will not. Remove the tachometer fitting first, (on the top), then removethe 10mm bolt which pins the bushing in place (side). I use a homemade tool to pop the bushing out. You may be able to grab the tach drive and pull upward bringing along the bushing. Be sure to remove that 10mm bolt which pins the bushing before trying to yank the bushing out. Inspect the bushing, the verticle and horizontal worm gears for wear. Make sure the oil pump turns freely also.

Thanks, I'll try taking out the drive today. The actual shaft was severely damaged (bent apart) where the top of the oil pump engages into a groove or slot (fork) in the bottom of the tachometer drive shaft. So far I can't tell whether the bushing that locates the shaft is damaged too or whether "normal" wear and tear forced the shaft end apart. The oil pump appears to be intact. I just hope the bearings are too. I'm going to take a few bearing caps off today as well, just to inspect and to measure the bearing clearance with Plastigage. Please let me know if anyone is willing to part with their tach-shaft (not out of your own car). Otherwise I'll try to repair mine or go out and order a new one.

According to SLS (parts vendor in Germany) this shaft is sold as a set with the one perpendicular to it (the one that is driven by the timing chain) and you are looking at close to $500. You might be better off with one out of an old block, i.e. a used one from a source that sells used parts?

I wanted to make sure I'm doing this right. I was just barely able to squeeze the aluminum housing and brass bushing that you mentioned past the cylinder head so that I don't have to worry about taking off the head at this point. However, the shaft stayed in. I believe it should just come out to the top as well. if that is the case then mine can't because the fork that interlocks with the oil pump drive shaft at the bottom end is spread (bent) so far apart that it prevents it from moving up. (I know, I always experience all the problems that no one else ever does). Also, there is some slight scoring of the brass bushing inside the aluminum housing so that I will replace that too if it's available separately. It's not enough damage to have been the cause of the problem, I believe. Finally, if I can't easily locate a spare shaft, will a non-tach drive assembly fit together with my auxiliary shaft as a temporary solution?

Well, I finally, had some time and not only made some serious progress on replacing the vertical oil pump drive with a non-tachometer, sedan unit for now. I also found the reason for the fairly violent destruction of the tangs on my old vertical shaft and the damage to the top of the shaft of the oil pump as well. A circlip had popped out of the oil pressure relief valve located in the oil pump. Unfortunately it had no where to go but jam up the gears of the oil pump which halted the pump instantaneously. Since the engine kept on running something had to give, namely the two shafts. This whole procedure obviously didn't make a lot of noise which is not too surprising, but there still remains the question of whether the lack of oil pressure did any damage to the engine bearings. Well, so far I removed the two lower connecting rod bearings that I could access. They appear to have a wear pattern that I would consider normal on a strong original engine that I presume had never been rebuilt. There is some very slight pitting and very limited and minor scoring , but never through the first layer of the 3 layer babbits (I never quite understood how dirt large enough to score the bearing halves could get in there, maybe at assembly?) The clearance as measured with Plastigage is about 0.045mm but so far I haven't found any specs in the BBB to tell me whether that is within normal tolerances. I haven't had time to check the crankshaft bearings yet. One more thing, I replaced the damaged shaft in the pump together with the matching gear from a used pump (I wanted to keep my old 130 part number housing). Is there a torque figure for the pump bolts? When I torque them down too tight I get a slight drag on the pump gears which I'd like to avoid for comfort's sake. Are these gears so precisely matched to each oil pump housing? Finally Joe, the used vertical sedan assembly also has some slight scoring on the top bushing. I'm sure it would work as is, but I may shim it up as you said. I don't have a lathe though and I was wondering what you do. Do you flatten the face of the bushing? What do you use for shimming it back up? How do I know how many shims (or mm) to use, as it would be hard to see exactly at what point the aluminum housing's upper flange comes to rest on the engine block when I insert it?

Joe Alexander: Hello Tom, Sounds like your on track. The factory spec. for permissable bearing clearance for the connecting rod bearings is 0.045 to 0.065 mm. for the main bearings the clearance is 0.035 to 0.055mm. It sounds like you may have lucked out. If you do not have a lathe, you can finish the bushing using some 400 grit wet dry sandpaper on a flat glass plate. Use a soapy water or oil to keep the paper clear. Rinse parts thoroughly when finished. As far as shim washers, many possibilities. Just something to take up the space. The bronze bushing will do most of the work. Machined shim washers work best (available in .001" thicknesses), but almost any solid bronze, steel, copper, or aluminum seal ring will work. You can adjust the thickness by working it down on the glass plate and paper. Insert the gear, bushing and pin, grab the top of the vertical gear top with some needle nose vice grips or such and check the up and down movement. Choose a shim or shims to match the movement. Repeat and adjust as needed. Try to get it so the pin locks down the bushing with little or no up and down play in the gear. The oil pump will get tight if its housing is tightened down too much. A little drag should be ok, it will work itself out. The torque specs on the engine bottom end, uses torque then angle of rotation. The bolts are stretch bolts. If you are not familiar with the process let me know. Also any W111 220-SE, 250-SE 280-SE chassis COUPE will also have the tach drive style gear you need.

Dan Caron: I believe that the 230SL uses a different oil pump than the later cars. I've seen oil pumps with an external oil pressure relief valve on the bottom of the pump. Any engines with a ribbed oil pan use this type with a short rubber tube on the strainer bottom. If it were me , I'd be inclined to install a new oil pump after having something get stuck in it. There's no real way of knowing if any unseen damage was done. A new pump producing maximum pressure may actually save you if there really is some other damage. Not worth the chance.

Tom: Please indulge me when I tell the following experience I just had this evening at 9 o'clock as I'm trying to do some work in the rare rain in L.A. If I sound a little proud during this, I'll admit, it was a fairly satisfying repair. Well, I was just going to install the shaft from the sedan when I noticed something like a screw head sticking out of the "junk yard" part I had just gotten. Sure enough the top had a 5mm Allen, but the screw wouldn't budge. I was wondering if I had possibly stumbled onto something that you maybe weren't aware of (or had just forgotten). Maybe the extra portion of the vertical shaft, that's used to drive the tachometer was simply screwed on to the otherwise identical sedan vertical shaft. I tried to use a torch and the screw still wouldn't budge and the Allen head was starting to wear out. So I considered the direction in which the shaft would be rotating (I figured that out from looking at the way in which the damaged oil pump shaft had been torqued. So I realized that the screw would have to have a left hand thread in order to prevent accidental loosening. With some more heat it came out and so I went to work to unscrew the important undamaged section of my original shaft in the same way. Well, it kept turning and turning, but didn't unscrew. It was a press fit with splines on the male end. So I drilled out the threads on the junk yard shaft, put some loctite in and created my own press fit to create my own brand new 30 year old shaft for under $10. (The new one lists for over $500 in case anyone was curious.) Anyway, it really feels even better to resurrect these cars with parts off cars that were ready to go to the crusher. Don't get me wrong, if I felt I was taking a big risk of damaging the engine I would have gone with the new parts, but I feel that the worst that can happen is that the shaft may eventually wear conventionally (I think the chances of another catastrophic failure are very minimal) and then I would have the oil pressure gage there to warn me. Joe, I couldn't find any injector rings to shim up the bronze or Brass bushing, but I found that the shims from the barometric compensator have the right size you described. Anyway, how's that for an exotic failure and a very fun repair aided immensely by Joe Alexander's very quick and clear directions. If it doesn't rain here tomorrow (normally a good chance in L.A.), I could know by afternoon whether the whole ordeal cost me any real damage to the engine.

Well, I got excited a little too early with the bearings. The big end bearings seem okay, but the main bearings are outside the wear limits. These seems odd to me. Why would the main bearings wear more the oscillating connecting rods? Anyway, the play is about 0.08 for two of the mains with moderate scoring in the first layer of the shell. The main bearing closest to the timing chain has a play of about 0.1!mm. It has two fairly deep score marks that go all the way through to the next (copper) layer. I'd say none of the wear that I'm seeing is due to the recent failure of the oil pump, but rather regular wear over the course of 30 years. My question is the following. I'm more of a practical, I'll take my chances kind of person despite having my masters in engineering (I know the engineers may sneer at me for my careless attitude. So, I'm not going to remove and rebuild the engine at this point, maybe two or three years down the road. My oil pressure before the incident was great and there were no sounds coming from the bearings to indicate that the main bearings were about to disintegrate. I am just wondering what harm can be done by just replacing the one known bad main bearing half that I have access to. I know this is completely unorthodox and I would never do it on anybody else's car, but I feel that if anything this can only give the crankshaft a little extra support that it wouldn't have otherwise. I know it would be uneven because I'd be replacing only the bottom, but does anyone have a very good reason not to do it? I also can't figure out how the small little rubber seal ring inside the bottom of the oil filter cartridge housing is removed and installed. How about the big one that goes at the bottom, just around that other smaller one?

Tom Hanson: Would it be all that big of a job to pull the engine, clean up the crank and put bearings in it? Somehow this seems like you may end up spending more in the long run. I could be wrong. I haven't patched an engine back together in about 33 years. Food for thought.

Cees: there were a couple of posts on how to replace the bottom oil filter seal not too long ago I believe. Anyway, it is best to leave the small seal underneath the cap in place if you don't have a leakage problem because, in order to replace it, you have to push/pry off the metal cover it sits underneath, and you could damage the metal. It is quite tightly fitted. The seals apparently almost never go bad. The larger one you can take out by pushing it outward from under the metal cap, with a pointed object like a nail (you will discard the old one anyway) and, once you have experience how to take out the old one, you will easily work out how to put in the new one. I used a wide screwdriver the last time I did this, to work the new seal under the ridge of the metal cap.

Joe Alexander: the problem with opening up a high mileage engine is that when you get inside you will find a lot of marginally worn parts and there may be no place to stop. Once you get going hold onto your wallet. Pistons, bearings, oil pump, gaskets and seal kit, timing chain, waterpump, should do the head work also, some valves, guides, sprockets, chain rails, not to mention the machine work and head work. Then hope there are no surprises like cam or other valve train parts. You may as well replace all the oil and coolant hoses, would hate to see that new engine go up in smoke. The other thing is if you are a little new at this, do you really want to risk making a mistake during the process? You also must consider the investment in tools and equipment you'll need for the task. The good thing is there are a lot of us out here that can help and advise. Yes I must agree that if you can afford the big expense and the downtime on the car now would be the time to do the work. However make sure of your findings are correct, if in doubt about the condition of the engine. At this point a few hours of work will get it running and the oil pressure will tell the story. If the engine is hurt and deteriorating it should not be used. Otherwise if the engine and oil pressure is as before it should be safe to use until you are ready to do a thorough job.

Tom: Once again, your answers are right on the money. I did feel that the main bearing wear appeared to be from normal use. I have no delamination, galling or scoring on the crankshaft and the crush is still there. I wish I could send you a picture, but I'll try to describe the wear pattern of the lower half shell closest to the timing chain. I the center there are two grooves that look as if they had been machined there, exactly like a double yellow line equally dividing a road. One groove is about 0.5mm, the other about 0.8mm wide and both are about 0.2mm deep. If they were not there when the shell was new, they were formed maybe if the top shell has a corresponding groove in it as the imprint of the ends of the lower half seem to indicate. I guess foreign matter running through the top groove may have eventually cut the somewhat irregular grooves into the bottom half although that may seem a little far-fetched? For about 2 to 3mm left and right of the grooves there is copper showing through, virtually on the whole (half) circumference. A very similar ring of copper barely shows through towards the edge of the shell as well. Pitting and foreign matter embedded in the shell is not that bad. As you said, one may still consider this normal wear if it weren't for the clearance of 0.1mm. Now, I was only able to put Plastiguage into the lower shell at two points each about 10mm from the lowest point of the cap, but this is the same procedure I used on the big end caps (even one strip only) to get a play of 0.045 on those bearings. I torqued the main caps to 8mkp in stages. The big ends at 4mkp, then 1mkp more, then 90 degrees more. Is this correct? Also where in the BBB do I find the allowable tolerances if they are in there? Also wouldn't the fact that copper is showing substantiate this kind of "outside the tolerances" but not terrible wear? The upside is that the shell appears quite normal on about 1/3 of its surface area and the wear is distributed evenly around he circumference. I have the feeling you will tell me that the shell is not that bad, which I like. Either way, it doesn't change much, just my level of confidence in the engine over the next few years. By the way, what an intricate oil filter system. That metal ring is not numbered in the parts illustration which is why I was thinking it didn't come off. I damage it when I tapped it back in, but it shouldn't affect the performance. The bolt seals snugly now. Is the cap available for the next time around? I also would like to know how many of our members are missing the same seals that I was for who knows how many years, thereby continuously letting unfiltered oil past the filter. Please check them all on your next filter change. Joe, thanks very much for all those valuable details. I know I'll make that trip to Blacklick, Ohio one of these days to say hi. P.S. I just crawled back under the car to look at the crankshaft. It is completely smooth with no grooves and the top shell of course does have that groove that I suspected might cause the grooving of the lower shell. (Is that right?).

Best is to replace the mains. If you can get at them all, by loosening all of them together (don't take them all off at the same time) the crank should drop just a fraction (all you need is a 1/64th of a inch and you should be able to punch out the top half of the shell (watch the direction of rotation as the shell has a notch on one side to hold it in) and insert a new one. Check the journal and if it has any spots that caused the scouring use some crocus cloth around the crank at that spot. When you put it all together have some shim stock of various thickness on hand. If you have too much clearance put fine emery cloth on a piece of glass and hone the ends of the bearing and put piece of shim stock behind the bearing (at least 0.001" less than the gap you want to make up) and check the clearance. Go back and fourth until it is right. This can take hours of time, not a Saturday afternoon job, especially the first time. The other way is to just do part two, i.e. hone the ends of the bearings and shim the caps. Doing this you must also pay close attention to having everything very very clean. Double solvent bath, etc. don't forget to pre lube the bearings when you put them together the last time. Start the motor up, bring it up to temperature, then change the oil filter to reduce the risk of a clogged filter running on bypass later. If the filter has done it's job, it takes about 90% of the particulates out with each flow through, but since the flow is not linear, i.e. oil splashes and moves so some old oil is always in the pan, it takes many passes to get the oil "clean".

You're much better off in the long run to do this right. These cars are just too nice to try to take what amounts to be a real short cut. Even if the crank feels smooth, it probably isn't. The other thing you need to be wary of is that the crank may have some ovality to it and once you've taken the shells out, chances are they won't set exactly the same as they did before you removed them. Consequently they'll go thru a slight re-bedding with more wear on the shell and crank.

There is always option 3, find a good running 280-SE sedan engine for about $500. And enjoy driving your 113 until you have the time and money to do a complete rebuild on the original engine. You can take your time and still be using the 113. When the original engine is finished and back in the SL, you will have a lot of valuable spares from the sedan engine. Anyone installing a sedan engine in a 113 must remember to switch the aluminum engine supports. The sedan supports are different and if left on, the engine will set too high in the SL engine compartment. The first time you hit a bump while driving your engine will dent the hood!

I went out and found a pair of standard main bearings today from a guy who rebuilds these engines. He looked at my old one and confirmed that it was quite worn, he could not say from what. Anyway, the new bearing was about 1.3-1.5mm wider which worried me a little. It had a 180 parts number which I don't recognize, compared to the 130 original bearing. Both were Glykol. The guy said not to worry and I thought, if it goes in, it would actually provide more support than the old bearing. The top half of the old bearing didn't look as bad as the bottom and the new ones slid in fine. By the way, the thickness of the new shells measured the same as the number 2 mains that came up as "worn" with the plastigauge, so I only replaced the number 1 set. Maybe the main bearings can't take the one sided measurement the way the big ends can? I put everything back together again and after checking for oil pressure it fired right back up again and ran as before the pressure loss. I'm quite confidant at this point that this repair can last me quite some time and that I may have eliminated the one weak link in the bearings. I poured in regular 20W 50 oil to flush the engine. How soon should I change again to make sure that it had time to filter out the "assembly dirt"? My home-made tach drive shaft seems to work fine too, so I can finally move back on to painting my dash which I was on my way to do when the pump jammed.

Looking for a set of new or clean used stock bore pistons for my 1970 280 SL. The engine number is 130.983-12-010550 I could take 4 pistons if they are the 4 ring version. I am trying to put this thing back together without boring the block as the bores are good and I would like to save 1rst and 2nd oversize for another day. Stock bore pistons will have 86.50 stamped on the crown(could be 86.47 up to 86.53).

Joe Alexander: be careful here Pat, cylinders do not wear round. Just re-ringing and engine puts new round rings in oval shaped cylinders! Check the Mercedes specs for allowable cylinder wear (.005")? I believe that allows a ridge of just a bit more than .002" on each side of the cylinder! OEM Mercedes rings are extremely expensive. Aftermarket rings may give bad results. My experience with putting new rings in used cylinders is oil usage of 500 miles per quart of oil or less. Bored cylinders can always be re-sleeved back to standard if you run out of room. I am not saying it may not work, but just sharing some information. In addition a correctly rebuilt engine may last the rest of your life. How is it that you are in need of pistons? Broken or worn ring grooves?

I need new pistons due to 21 years of storage. The really interesting thing is the pistons corroded to the cylinder walls and the cylinders show no rust. I guess the pistons must have reacted with the decomposing oil in the pan. I have run a bore gauge down the cylinders and they show less than .002" total wear. Those cylinder walls look pretty close together and I thought the additional meat of stock bore would help to keep it all stable.

Dan Caron: I use Deves piston rings for such jobs. If I use new pistons then I use the rings that come with them. I've found that Deves rings give the best results in partial rebuilds. Not everyone can spring 900 to 1200 bucks for a new set of pistons when they can re - ring the pistons. There's no way I'd use Mahle or other OEM rings - they just don't work well unless you rebore the cylinder. In that case they work very well.

Thanks for the tip. I used to work for a man who was fanatical about Deves rings but he would never say why, he would just mumble something about Swedish Steel(since he was a sweede I didn't pay him to much heed). I have found Mahle oversize pistons for $350 and I have a very clean used set but was still hoping to get the stock bore if I could.

I was assembling my engine this evening and was lashing the valves when I inadvertantly turned the engine in the wrong direction. I was quite suprised when I heard the timing chain slip on the crank pulley causing the engine to go out of time. Assuming I bled the tensioner correctly which I am pretty sure I did and that the tensioner was assembled correctly which I verified with a manual and double checked, Is this normal? It seems one of two things is happening here. Either the chain has stretched more than I though(engine only has 60K on it) or the tensioner is just a dumb design and hopefully there is an updated version. Any help here would be greatly appreciated.

I am currently putting my engine back together, it had sat for 21 years in a heated garage. Unfortunatly the pistons had corroded so badly that they were stuck in the bores(no real rust to the bores so not a moisture issue). I have never seen this sort of seizure before and I assume that it has something to do with the metalurgy of these pistons. The bad news is nothing I tried worked and I ended up smashing the pistons to get them out then rebuilding the engine using a set of used pistons that I bought from a fellow board member. In playing with my pistons after the fact I think they would have responded better to laquer thinner. The only thing is that the corrosion was pretty pervasive and almost looked like varnish on the cylinders and many of the rings were stuck so I honestly don't know if I would run it without teardown.

Joe Alexander: These tensioners are spring and hydraulically actuated. Pour some motor oil in the pocket in the head where the tensioner actuates the chain tensioning sprocket. Pump the tensioner up by moving the chain adjusting sprocket up and down until firm. Normally a new chain will not jump time under the conditions you described. A stretched chain, and unprimed chain tensioner along with turning the engine backwards will cause the chain to jump.

I did prime the tensioner with oil. I guess I will put a new chain in it for safety's sake and take a hard look at making some sort of hybrid tensioner. There have been alot of advances in the past 30 years.

Bernt Damm: Question is, does your tensioner actually work? In fact, it is an automatic tensioner which adjusts itself to whatever slack the chain produces (within limits but if your chain is streched too much, you won't be able to get the valve timing right either). It has a one way valve inside it and a spring. The spring pushes the tensioner against the chain to take up the slack. In doing so, oil enters through the one way valve, filling the volume created by the forward movement of the spring and piston. This oil can't escape back out and therefore it locks the tensioner in the position the spring put it. Initially, the tensioner needs to be primed and bled by repeatedly pushing it back and forth with a screwdriver until it becomes impossible to move it at all. The design of this tensioner is not a problem and MB used it right up to the 80s or even 90s. When you primed it and bled it by pumping the tensioning gear left, it should have become a solid resistance. If it did, then there is another problem and if it did not, either there is no oil or the ball inside it is missing or something else went wrong with it.

Joe Alexander: your error was turning the engine backwards. That's a no no especially with a used chain. The tensioner will deflate eventually if you apply a constant steady force and the chain will jump. These tensioners are very reliable and seldome fail. There are no soft parts to wear out (seals or o-rings) as in later MB designs. Just set it back up and avoid turning it backwards. A new chain is always good insurance. Be sure to use the original Mercedes "jwis" brand.

Does anyone know if the rubber valve guide seals are still available anywhere? My 67 230sl recently came out of the shop after a rebuild, and then started smoking again after a few weeks. The shop found that one of the teflon seals on an exhaust valve had popped off. They got another one and installed it and it did the same thing. They have tried to get the original rubber ones but have been unable to do so, so I am checking here to see if anyone knows if they are still available and if so, where? Thanks for any help you can offer. By the way, another subject, I had asked previously about cold starting and it was suggested I hold the key in the on position for a bit before starting. I responded that it didn't work the first few times, but now would like to report that it started working just after I said it wasn't. So I owe another thanks.

Tom Hanson: I can't remember far back enough to have seen rubber seals for a 230SL. Maybe new guides and fresh factory teflon seals would do the trick.

Dan: 230SLís usually donít have rubber exhaust valve stem seals. The whole set is Teflon or some type of similar material. Iíve had them pop off too and found that you only get one chance to put it on right. Having the right tool to do it and knowing how is the key. The valve guide and the valve stem has to be completely free of any oil or it wont stay on.

The original valve seals for your 230-SL were the white teflon like style. The later rubber like valve seals were introduced in gasoline Mercedes engines in the 70ís after the 113ís. The 230-SL valve guides had no groove in the top of the valve guide to help hold the seal in place like the later 113 engines. The seals for these guides were unique, compared to the latter 113 engines. Possibly the metal band spring type instead of the later metal wire spring type.? Be sure the shop is using the factory correct seals. If the correct version seals are being used, and the seals keep popping off you may have another problem. Letís hope not.

I had the same problem when I rebuilt my 230 engine: after mounting the teflon seals the oil consumption was very hight about 1Kg. per 500 Km. I had to substitute those seals with the old rubber/metal and now everything is right. If you email directly I can help you to find them.
< Removal and installation | Main.TrailIndexPage | Compression and compression testing >