timing chain
 

How do you know its time for a new timing chain? I have a 1976 240D, starts and runs great. I have most of the records but no evidence of chain being replaced. 250000 miles. The car does make a slapping noise until its warmed up

I have illustrated....
 

...how to do this on my web site. While this was on a V8, the process for your diesel, as far as determining stretch goes, is the same.

Go to Cars-Technical-Motor, and look at both the 'Chain Rails' and 'Timing Chain' pictorials. Between these two you shoul get the idea.

You will have to remove your valve cover to see the cam timing marks, and (probably) your fan to allow you to rotate the engine manually.

Leatherman,


Your in the wrong spot on the manual. What you are reading is how to check chain setup with a dial indicator. That's ussually only done when the engine is assembled, unless the head is milled at a valvejob.

Rotate engine at crankshaft slowly until the camshaft alignment mark matches is in the correct position. Look down at the crank markings- see how many degrees of stretch you have.

Note: must turn in correct engine running direction.

I'd personally replace a chain by 250,000- they are too cheap and installation is not overly difficult.

Generally, replacement is by degrees- 4-5 is time to replace. Good measurment by this "eyeball" method is proably good to 1 degree or so.

Michael

Oh,

This proceedure is outlined in the service manual- not the engine overhaul manual. So, I'm told.


Michael

Hey,

Why would the base timing change??? That's my point. IF your going to do that- you better start and make sure tdc is correct on the crankshaft.
Really don't care about other's views Leatherman, both methods are in Mercedes service litature. I was trying to point out that your statement that it had to be done with a dial indicator is WRONG. I still stand by that..

We're checking chain stretch-not engine setup. I'm talking 15 minute check- your talking much more time. How accurate do you need to be anyway.. diesels don't seem overly sensitive to timing.

I'm a lazy IP adjuster... I'd rather set an engine up, run it until 2-3 degrees of strech and replace the chain.


Michael

There are also offset woodruff keys available to correct the cam timing. These can be used to correct for an elongated chain or a milled head. Milled head won't affect IP timing.

As long as the chain adjuster can take up the slack in the chain, the chain does not have to be replaced.

P E H

IF you want to qoute,


kchemers was looking for how to determine if a timing chain stretch warrented replacement. To which you replied

"Remember that the factory shop manual calls for measuring the movement of the intake valve on the front cylinder. This is usually done with a dial indicator. although any accurate measuring method would be fine. Beware of any method which does not use the intake valve as the basis for using the crank position to determine chain elongation"


using the dial indicator method while effective is over kill... just like me wasting my time on this discussion =( Look at the MB service liteature- it's on the cd's. The method of rotational check of chain stretch, is listed. I think that came out with the 1986 litature, but is applicable to all MB's.

Why mention my laziness? Because, I've got the tools. My 617.912 engine requires the drip-timming or other manual methods and it's a slug when timing chain stretch gets high. With the IP setup- it's easy to roll a new chain in the engine with a valve adjustment.
For later cars, I use the electronic IP adjustment which is 10 minute job. So, there my options are more.

With any car I own or work on- I set them up the first time... from there it's easy. Every check camshaft timing on 911/930's. It's amazing how bad they can be out from other mechanics playing... It's a manditory part of the first tune-up I do. Customers were always amazed at the difference. On those you can tweek the engine retarding and advancing the timing slightly depending on what displacement we're talking about (2-3.2 litter).


Michael

Thomaspin,
Great site! Just one question, what's a distributor? I remember reading once about wires and spark plugs but have forgotten what they're for.;)

Irg,

A distributor is the thing with wires coming out of the cap on my old IH tractor that starts the Diesel engine on gasoline. That IH Diesel engine also has a coil and spark plugs and a carbureator. Do you know what those things are?

P E H

P.E.Haiges,
Nope, never heard of them, but I'm sure they're important to some people. I once had a car that wouldn't start due to a wet distributor. Haven't had a problem with that yet on my diesels.
LRG

I had the same problem on an old Valiant. The inside of the distributor cap had condensation on it. Blow job from a hair dryer fixed it.

You are right, never had that problem on my Diesels.

P E H

short SAID by Mercedes, it is time to change cam transmission chain WHEN it is getting noisy, u should replace the hydraulic tensioner at the same time...


that is WHEN u should change it...



BMW says u never need to change their chains... on an engine liftime.... =)