After getting my 1984 380SL in perfect running condition in every respect (tons of power, ice smooth idle, just a pleasure to drive) I now have something that is worrying.

First the background, which is that about 2 years and 8000 miles ago the timing chain broke on the car and lots of work was done in the engine, all of it well as far as I've been able to see to date.

Recently the car was in front of a few mechanics and finally back to me where I fixed a number of mechanic mistakes myself and then fixed some other things. Anyway, the car runs beautifully.

One thing I do know is that a suspect mechanic did adjust the timing on the car amongst other things. The car has a new catalytic converter and pre-cats in there.

At any rate, now when the car sits for a few days and is started for the first time (thus cold), I hear a very brief sound from the front of the car that reminds me greatly of the chain slap that I heard before my car originally broke its timing chain. However, the sound is shorter than what I remember it doing before (you may hear it for maybe 1 or 2 seconds, before maybe 4 seconds). WHen it did it before, I thought it was perhaps something in the exhaust shaking. Now of course I'm not likely to accept that explanation anymore. If I turn-off the car after it makes the noise and turn it back on, you hear nothing and you will hear nothing again on the car turning it on or off or when driving. It seems to happen when the car has sat for a few days and is completely cold.

I suspect that the answer from the group is that I have to go in there, remove the valve covers, and look at the tensioners. Also, how would I check chain tension? I can go look in the manuals and will start there but if there are any rules-of-thumb/DIY tips I'd greatly appreciate them. Also if you have any other theories on the sound, I'm very interested. Any other explanations for the noise. Also, is there ANYTHING that a mechanic can do that is "dumb" that would damage a tensioner, stretch the chain, or break a tooth (would there be other symptoms of a broken tooth)? For example, adjusting the timing in some sloppy manner? And finally, there is some of that luby valve cleaner in the gas (it's like fuel injector cleaner). SOmetimes I wonder if, at a cold start, that stuff doesn't raise the octane so much that it causes the timing chain to flop a bit from all of that power at startup.

Has the car been updated to double row chain??????

arthur, this car was manufactured with a double row chain. I cant understand why I have this issue now. It seems there can be no peace.

I thought some '84s still had the single chain, but I guess not .

Anyway, I think your tensioner may not be holding oil pressure over-night

380sl timing chain tensioner adjustment?

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1D00YU6RY1D61563ZX&year=1984&make=MB&model=380-SL-002&category=A&part=Timing+Chain+Tensioner

That's where I would start too.

[QUOTE=ericgr]After getting my 1984 380SL in perfect running condition in every respect (tons of power, ice smooth idle, just a pleasure to drive) I now have something that is worrying.

I suspect that the answer from the group is that I have to go in there, remove the valve covers, and look at the tensioners. QUOTE]

I hope you find something minor wrong but I would pull the valve covers and look at the guides before driving it again. Chain tentioners are about $100 US and guides are $10 each. Valve jobs are $3 to $5 grand. Check the chain guides first.

$70

FastLane

I don't believe any of the 380's had a double row chain from the factory.
I'd definitely put a new chain tensioner in it, easy job, no need to even remove the valve covers. I can't believe the mechanic wouldn't have replaced this automatically when all the engine work was done, as a matter of fact I'd check the records to make sure it wasn't done and chew him out good if he didn't, and ask if there is warranty on the part if he did.

Gilly

PS I don't think the simplex chain is available as a replacement part any longer, not from MB anyways.

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I have to believe they changed it, it is on the ticket. The mechanic that did isnt the nut case I otherwise had problems with, they are just expensive and usually nasty (others say the same thing). Anyway, I looked at the MB shop documentation, I cannot tell what if anything I have to trmove to get to the tensioners. Where are they on the 380 engine? Do I have to remove anything toget to them?

MB changed the 380 to a double row chain in the early 80's. I think I would check the chain tensioner also...It is easy to remove...you need to buy a Haynes(??) book for the 380 and other engines...I have one and I will look tomorrow and get you some information about the chain tensioner...Jim

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James A. Harris

MB "HAD" them changed to double row in the MID 80's, but I believe they all LEFT THE FACTORY with a simplex chain. MB would pay to have them changed. I will see if I can definitely confirm this.
The tensioner is on the side of the right cylinder head, above the alternator. On some models you may need to loosen the alternator belt and allow the alternator to drop to the side out of the way. The upper bolt is sometimes hard to get too, but with a little ingenuity it's an easy job.

Gilly

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OK, the repair disc sez the simplex chain was installed "up to model year 1983", I assume that means 83 and newer are double roller, my bad.

Gilly

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Thanks, I will look for the tensioner by the alternator in the morning. I will also check chiltons in addition to my MB manuals. Any other tips on changing the tensioner would be really appreciated. I noticed in an old post from Steve the moderator that these tensionere, even when changed and new, can have a problem holding oil (my memory, probably not acurate or as he said it) and they can make a noise. Maybe the tensioner has gone south for some reason. I do have 20w-50 oil in there now but it is still warm here, like 60 to 70 farenheit. There was some Castro 5w-30 synthetic in there about 600 miles ago briefly. I cant believe this would matter...my head really is exploding. I have gone from years and years of peace with this car, to a relatively small period aggravation, to a small period of peace, and now back to yet another mystery.

It's beneath the oil cap on that cylinder block, just underneath the valve cover-- right in that area. Looks to be installed with two simple bolts. I haven't changed one before, but it looks simple per Gilly's post-- remove the two bolts and replace it. After listening this morning I am not certain this is the timing chain, I'm still wondering. It seems to happen has it has turned colder here. I'm going to look closer at the sound when it starts up and also check further around the car for more information about what it might be. The fan shroud looks fine, I replaced the fan clutch so no noise from there. It didn't seem to make much if any noise this morning.

I have 20W-50 in there and while I realize this probably has nothing to do with it, that weight is a little heavy for this area as it gets colder (we dip below freezing). I'm going to drain that and put a thinner oil in there. For troubleshooting this I may use some Mobile One even though I know this will increase a very very small oil leak between the oil pan and transmission (that gasket) which I know is all but guaranteed as a leak on these cars 100K plus. That's the only fluid leak in the car as an aside. Thanks again for everyone's help. Any further thoughts on changing the tensioner (tips, etc) would still be appreciated. I looked at Chiltons and they suggested what I was thinking based on what I learned in posts here-- that you put the tensioner in a container of oil and you depress it so you can fill it with oil before putting the new one in the car. This makes sense to me, I believe this is a good thing to do before install (?).