Marshal:
Concerning rebuilds and factory engines on the W115 -- MB had quite a
few problems with pre-mature wear on that engine, and factory originals
are prone to excessive cylinder wear. A miss-match between piston,
sleeve, and ring types will also do the same thing on rebuilds.
My friend remembers them being replaced a lot under warranty (or
rebuilt with high nickel sleeves and different pistons) -- and today
one with 150,000 original miles may be a smoker. Terrible head
cracking problems during the 60's as well, during which time his father
stopped using MB diesels in his taxi business. MB was eventually
forced to give extended warranties on heads by the German government.
Something about taking the head design away from the actual producer
because it was cheaper, then changing it, somewhat less than
successfully.
I agree that rebuilds done in the US can be horrible -- if not done to
MB tolerances, you can end up with one burning a quart of oil in 200
miles within 10,000 miles of rebuild! Some are so sloppy the rings
never seat -- my brother and I got one like that to replace his 617
with a broken crank (again, a crappy rebuild -- orange silicone slopped
all over the oil filter housing gasket, a big slug sat on the #2 main
oil hole --- you can guess the result). That replacement engine had a
ring ridge almost 0.015" deep! Bore was 0.005" larger than the piston,
pistons had extruded ring lands, crank was ground to the nearest SAE
dimension SMALLER than the minimum metric size allowed, was only smooth
and shiny where ti ran on the bearings, valve were way beyond terminal
wear, and the valve guides were all 0.005" or more oversize. I don't
think it ran long, I'm quite surprised it ever started. I don't
remember what the bearing clearance was on the crank when we got the
engine, but I think it was 0.005" or more.
We rebuilt it properly (after much discussion about valve guide
clearance at the machine shop), and it's been running for six years now
-- starts instantly no matter how cold it gets, very little black smoke
and never uses oil between changes. Has 45 lbs oil pressure at idle
hot unless you just pulled off the interstate!
Peter
