Timing chain, good advice or bad? - PeachParts Mercedes-Benz Forum

jbach36 · #1 11-01-2015, 12:22 AM

My 24 year old car turned over 200k miles last week. I was previously told to have the timing chain replaced at the 200k mark. The conventional wisdom that I've read on this forum is to not just replace it rather than check, since you're going through all the effort to get to that area anyways.

I called a place that specializes in replacing belts and chains to have this done, and much to my surprise, he said unless you hear the chain rattling, especially on a cold start, don't replace it. He said ALL chains when they begin to fail, or the tensioner or rails begin to fail, you'll hear the chain starting to rattle. The rattle is the precursor to ALL chains needing attention. No rattle, no worries. He said he's seen some Mercedes go 300, 400, 500k before needing to change out their chain. He said he'd be glad to take my money, but if it sounds normal, there's no need to bring it in.

Good advice or bad advice? It was from a guy who specializes in it, so I figure he's seen and worked on enough of them.

1991 300d, 200,078 miles

leathermang · #2 11-01-2015, 12:41 AM

Change the chain and everything which touches it in its travels. If you really like the car include the sprockets in that renewal.... as putting the new chain on the old sprockets will cause the new chain to wear faster and in a non standard fashion... but at the very least change the chain and the tensioners, etc..

MagicBus · #3 11-01-2015, 12:48 AM

Let me preface this by saying I'm not an expert...

But, I wouldn't trust my ears on this. I measure timing chain stretch and then evaluate the situation based on that. That's the only test I know of to properly determine chain condition.

leathermang · #4 11-01-2015, 12:56 AM

It is the condition of the things IN TOUCH with the chain which are more likely to cause a total wreck....
and to replace those without replacing the chain would not make any sense given the labor involved in them...and how cheap the chain is.

leathermang · #5 11-01-2015, 01:01 AM

Quote:

Originally Posted by jbach36

.....I called a place that specializes in replacing belts and chains to have this done, and much to my surprise, he said unless you hear the chain rattling, especially on a cold start, don't replace it. He said ALL chains when they begin to fail, or the tensioner or rails begin to fail, you'll hear the chain starting to rattle. The rattle is the precursor to ALL chains needing attention. No rattle, no worries. ....

Here is the bottom line for that guy...and anyone else that suggests you WAIT... will they pay the cost of whatever EXCESS damage that might occur due to the fact that you have an INTERFERENCE ENGINE ?
Meaning.....if the chain suddenly stops due to a tensioner breaking... and BENDS VALVES... requiring the removal of the HEAD.... to fix with a valve job.... if your engine does not make that ' help I am about to DESTRUCT ' noise to where you hear it ?

Jeremy5848 · #6 11-01-2015, 01:08 AM

You only have to pull the valve cover, an easy DIY job, to inspect the chain and measure stretch. My '96 E300 had about 1 degree of stretch, +/- 1 degree due to my inexact measurement, when I checked it at ~275,000 miles. I wouldn't change the chain at 200,000 miles unless I knew there was something wrong. If the chain is badly worn the sprockets should be changed too, as Leathermang notes, but that is a lot more work/money than just pulling through a new chain.

TopKnot · #7 11-01-2015, 01:19 AM

Unless someone knows the full and complete maintenance history of the engine in question it seems to me that after 200K they've got their money's worth out of the original chain. If you replace the whole shoot and shebang chain, guides, tensioner even a couple sprockets for $500 that's pretty cheap insurance for at least another 200K "timing chain" related worry-free miles compared to "waiting for "slap" to inform me the potential MTBF is nearing!!

sixto · #8 11-01-2015, 01:22 AM

Ordinarily I'd advise to let chain elongation decide but there's a TSB that describes a timing chain problem on 602.96s - http://www.w124performance.com/docs/mb/OM60X/OM60x_Timing_Chain_TSB.pdf

Sixto
83 300SD

Diesel911 · #9 11-01-2015, 11:21 AM

I say check the Timing Chain Stretch and go from there.

atypicalguy · #10 11-01-2015, 02:36 PM

Just checked mine at 190k on a 617.952. No detectable stretch. Zero. I mean not even a hint. I put the new head on and a new tensioner spring. The spring was worn nearly through on one side, so that is where I would focus attention. The rail guide thing had plenty of phenolic left on it. I have heard there were several versions of those chains; Mike Elias was rebuilding the head and he was not at all surprised. I have run synthetic in it since 82k, so maybe that had something to do with it.

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leathermang · #11 11-01-2015, 02:53 PM

Quote:

Originally Posted by atypicalguy

Just checked mine at 190k on a 617.952. No detectable stretch. Zero. I mean not even a hint......

You did not measure correctly.

atypicalguy · #12 11-01-2015, 02:57 PM

Ok enlighten me.

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atypicalguy · #13 11-01-2015, 02:59 PM

This is going to be one of those undisprovable without a photo kind of things. I turned the engine over a bunch of times from the crank to recheck it if that matters to you.

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leathermang · #14 11-01-2015, 03:02 PM

You went 80 k on regular oil.. then changed to synthetic.... right ?
Do you have any idea as to how many engine rotations you made in that first 80 k ?

Diesel911 · #15 11-01-2015, 06:31 PM

Quote:

Originally Posted by atypicalguy

Ok enlighten me.

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I believe he wants to know if you used the 2mm Method and if you did do you feel you followed the instructions correctly.

The reason for the questing is that in the firs 20,000 miles the Timing chain is expected to stretch a bit. That makes the zero stretch measurement suspicious; especially if the Crank and Samshaft Gears were reused.

Using the 2mm Valve Lift Method to measure.
On a 617.952 it has the intake valve opeing at 9 degrees after TDC with a new Timing Chain and 11 degrees with a used timing chain at begining apriximately 20,000 miles.

That implys that a new timing chain is expected show some wear at 20,00 miles and that is normal.