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  #1  
Old 12-03-2008, 01:39 PM
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M103 timing chain - should I?

They say these M103 timing chains last "forever".
Mine has approx 180k miles, and seems perfectly fine, with no noise, no visibly over-worn guides, no visible cam-timing change, etc.
Oil changes every 3-4K.

But, should I roll a new one in, just for preventative maintenance after 18 years? Not a lot of cost, I can do the job myself.

I had a belt tensioner break in half and strand us last year, so I'm sensitive to these catastrophic failure potentials.

DG

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  #2  
Old 12-03-2008, 02:54 PM
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I did mine when I did valve job at 142000, but it didn't need it but if you do also change chain tensioner just for prevention, if you valve timing hasn't changed you can hold off, my old 300d needed offset keys every 30-400000 and a new chain by 180000
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  #3  
Old 12-03-2008, 03:05 PM
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Don't forget to change the timing chain guides. Those would probably wear out before the actual chain.
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  #4  
Old 12-04-2008, 12:17 PM
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Thanks guys. Yeah, last time I had the tensioner out (120K or so) the plunger was only on the 4th "notch" of the 10 notches. But the idea of any chain going that many miles is pretty hard to accept for an old Chevy guy.
Does anyone ever bother with changing the sprockets?

DG
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  #5  
Old 12-04-2008, 12:36 PM
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I had one with almost 300k that was still perfect. With no signs of a problem I wouldn't mess with it. To mess with a working factory 103 timing chain is to introduce risk, not mitigate it.
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  #6  
Old 12-04-2008, 12:47 PM
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I wouldn't touch it

That is, not without having real good reason to replace some stuff. Going back the past 3 or 4 years, the number of engines that have been lost due to screwing with that chain have been many, especially on the 617 diesel. So unless you see real evidence of wear, I would say leave it alone.
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  #7  
Old 12-04-2008, 01:07 PM
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Quote:
Originally Posted by S-Class Guru View Post
They say these M103 timing chains last "forever".
Mine has approx 180k miles, and seems perfectly fine, with no noise, no visibly over-worn guides, no visible cam-timing change, etc.
Oil changes every 3-4K.

But, should I roll a new one in, just for preventative maintenance after 18 years? Not a lot of cost, I can do the job myself.

I had a belt tensioner break in half and strand us last year, so I'm sensitive to these catastrophic failure potentials.

DG
I wouldn't touch it, bottom ends have been known to last 500k+ with good maintenance. It may make sense to do if you're doing the top end but I agree with the other poster that you can introduce problems. An engineering term is that once you strengthen one part (or add a new part) you make the other parts weaker. That said, if the parts have worn equally then why add in a new part to the equation?

BTW, the tensioner (rubber) has a higher and earlier failure rate than the chain. There are many failures from untrained mechanics trying to adjust tension without loosening the set bolt.
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  #8  
Old 12-04-2008, 06:56 PM
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Okay, I'm convinced; she gets to stay as is. I used to race dirt bikes, and we never ever put a new chain on a used sprocket, same theory might certainly apply here. And, I wonder if the best chain you can buy today is anywhere as good as the OEM chain from 1990.

DG
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  #9  
Old 12-04-2008, 07:10 PM
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Quote:
Originally Posted by S-Class Guru View Post
Okay, I'm convinced; she gets to stay as is. I used to race dirt bikes, and we never ever put a new chain on a used sprocket, same theory might certainly apply here. And, I wonder if the best chain you can buy today is anywhere as good as the OEM chain from 1990.

DG
that metal has a shelf life, LOL

Seriously, with advances in metallurgy and technology new parts "should" be better but global competition has driven manufacturers to cut costs and produce inferior product to compete. Plus they are designing out the ability of DIY people like us to maintain or preserve the car...
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  #10  
Old 12-05-2008, 02:46 PM
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Quote:
Originally Posted by arvy View Post
Don't forget to change the timing chain guides. Those would probably wear out before the actual chain.
I agree. More work to get timing cover of though but if you have the time you might as well do it.
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  #11  
Old 12-05-2008, 06:12 PM
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I have a 1986 300E with 160,000 miles and how do you tell if the chain is going bad without opening it up? Does it make a certain noise?

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