A couple of years ago I asked the guy at the local MBZ wrecking yard how many miles I should expect to get out of my '84 300 turbo diesel (bought used w/ 185,000 miles), and he said 250,000. Well, he was right-- last winter I passed 250,000 miles and I had to start plugging in the block heater to get it to start in temperatures below 50F. So now I have the engine out, 265,000 miles and this is what I found: The major wear was with the intake valve guides-- they were flopping loose at 10-12 thousands when the max allowed is .004. The exhaust valve guides were maybe around .002 wear. There was a slight ridge at the top of the ring travel in the cylinders, and the rings were a little weak as compared to new ones. The rod bearings showed some discoloration from wear but were still good. The main bearing lowers I checked were like new with no wear noticed. The timing chain was still good as it had been replaced by the previous owner. So all I am doing is replacing the rings, honing out the cylinders; I replaced the intake guides, did a valve job and put the head back together with new seals using the still good springs. Left the main bearings alone and replaced the rod bearings and rod bolts/nuts. I also replaced the front and rear oil seals. I never took the crank out, and the cam lobes looked good. Cost? about $350 in parts and my labor. I could of bought a used engine with "good" compression for $900. Monday I'll put the head back on and hopefully by the end of the week I'll have the car running. I'm figuring it is taking me two weeks of my time to pull the engine, do a minimum overhaul, and put it back. There is no way this job would be worth doing on this old car if I had to pay a shop to do the work!
--Geoff '84 300D TD California