"jumped" timing on E300D

I had written a few days ago about my "Dead Diesel", and based on advice I got from responses, took the car to my local dealer for service.

They told me that the "Timing chain had jumped six teeth" and that is why my car had died. I don't doubt their diagnosis, but I just was hoping to better understand the reason for this.

I had checked the chain when I first got the car, and it seemed fine with no excess play. Why would it suddenly "jump" like this? I have heard of chains breaking, but I can't say I have heard of a chain slipping.

The only other question is when a chain slips like this, wouldn't it result it bending and breaking of expensive parts. The suggestion that I got was that some how only the timing of the pump was affected. Is this possible? Could only the injector pump slip timing while the crank and valves escaped unharmed or do you think it is just a matter of time before valve damage also becomes apparent?

I bought this car expecting years of service out of the diesel, now I may have to sell it to pay for the repairs. I'm beginning to think I should have bought a pre-1985 diesel as I never heard of this happening on one of those.

I eagerly anticipate any insight that may be out there. As you might be able to tell, I am really disappointed over this, but still hoping for the best. They won't actually get to fixing the car until next week, so for now all I have is questions. Thanks again.


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Tony B.
1995 E300D

Did you say YOU checked the chain when "new"? Or did you have an independent tech check the chain? Many times there were no obvious signs of problems with the chain itself, but more a problem on the camshaft sprocket whereby the teeth become worn and/or broken. Mercedes service literature says to replace the timing chain sprocket and tensioner with updated parts if you exceed 3 degrees stretch when measured at the camshaft to the crankshaft. Or if you see worn/broken parts as described above. If it infact that many teeth on the camshaft sprocket I would guess you did crash the valvetrain. Usually this does not hurt the pistons but it still could.

99 times out of 100 this problem is caught by a qualified tech before it becomes this big of a problem. Sorry for the lousy experience and bitter feelings you must have on this product. This is a very isolated case.


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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Mecredes issued a service info about excessive chain stretch more than 3 years ago so a good M.B. technician should know about the problem! A lot of chain problems were repaired by dealers while the cars were still under warranty! Mercedes tries to identify problems like this & warn their dealers about them.