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 firstname.lastname@example.org
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
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.
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.
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