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Car Forum / Mercedes-Benz Cars / December 2005How to measure timing chain stretch
The car is an 87 300D with 215k miles, I about to pull the head off to replace the head gasket (excessive blue smoke, carbon build up on #1 cyl injector) and would like to determine the condition of the chain (ie stretch at service limit) before the head comes off. Please respond to tavanas@gmail.com thanks >The car is an 87 300D with 215k miles, I about to pull the head off to >replace the head gasket (excessive blue smoke, carbon build up on #1 cyl >injector) and would like to determine the condition of the chain (ie stretch >at service limit) before the head comes off. They're good to about 100K. If you're going that far into the engine anyway, may as well just replace it. The timing chain is assessed as follows: Remove the valve cover. Between the chain's cam sprocket and the most forward cam support is a collar which has a notch in its outer radius. On the left side of that front cam support is a groove cut C/L to the cam. Turn the engine NOT by the cam but by the power steering pulley's nut so the notch on the collar is aligned with the groove in the tower. That's the cam's TDC. Then read the crankshaft's angle off the harmonic balancer. Replace the timing chain if that angle exceeds 5 degrees; i.e. that the crankshaft is 5 or more degrees ahead of the cam. Know that the chain also drives the injection pump so it's best to link the new chain to the old one and wind the replacement chain through, keeping tension on both ends so the chain's links don't jump a tooth anywhere. If it jumps the IP and the cam must be put back into sync with the crank. Suggest you look through the archives at www.mbz.org and check the diesel forum where there are numerous owners of sixes like the one you're about to repair. Thank you. On 12/5/05 1:25 AM, in article QdSdnWtGqpb5QA7eRVn-ow@comcast.com, "T.G. Lambach" <tlambach@comcast.net> wrote: > The timing chain is assessed as follows: > [quoted text clipped - 17 lines] > diesel forum where there are numerous owners of sixes like the one > you're about to repair. > The car is an 87 300D with 215k miles, I about to pull the head off to > replace the head gasket (excessive blue smoke, carbon build up on #1 cyl > injector) and would like to determine the condition of the chain (ie stretch > at service limit) before the head comes off. > Please respond to tavanas@gmail.com > thanks While the advice given by others is good and correct, replacing the head gasket is not going to address the problems you posted. Ok you got my attention, do you care to elaborate? thanks On 12/5/05 9:50 AM, in article G5SdnbjmC5sKzgneRVn-uw@comcast.com, "Chas Hurst" <hurst1@comcast.net> wrote: >> The car is an 87 300D with 215k miles, I about to pull the head off to >> replace the head gasket (excessive blue smoke, carbon build up on #1 cyl [quoted text clipped - 6 lines] > While the advice given by others is good and correct, replacing the head > gasket is not going to address the problems you posted. The head gasket has nothing to do with blue smoke or carbon build up on an injector. But a bad injector could do all that. Have you had the injectors tested or replaced recently? > Ok you got my attention, do you care to elaborate? > thanks [quoted text clipped - 12 lines] > > While the advice given by others is good and correct, replacing the head > > gasket is not going to address the problems you posted. i had the injectors bench tested for openning perssure and spary pattern and they all passed. > The head gasket has nothing to do with blue smoke or carbon build up on an > injector. But a bad injector could do all that. [quoted text clipped - 19 lines] >> > head >> > gasket is not going to address the problems you posted. Well, that takes care of the easy stuff. Sources for the smoke would include piston rings/cylinder wear and valve guides and stem seals. My '87 with 270k smokes at start-up and carries on for 5 seconds if the engine temp goes below 40 deg F so I use a block heater. Otherwise it runs fine and uses about a quart of oil between changes. The car is worth less than $3000 (as is yours) and that should be considered when contemplating major repairs. > i had the injectors bench tested for openning perssure and spary pattern and > they all passed. [quoted text clipped - 22 lines] > >> > head > >> > gasket is not going to address the problems you posted. |
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