Freshen up '84 300D Turbo Diesel

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 The timing chain was still good as it had been replaced by the previous owner.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
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Lemme get this straight- you took the engine apart without knowing what was wrong? The valve guide wear you mentioned is insignificant; the only way it would be unable to start without a block heater is if there were practically no compression (unheard of at less than 600,000 miles or so), or the glow plugs don't work (won't work with the "rebuilt" engine either).
Bill Ditmire Ditmire Motorworks,Inc. 425 White Horse Pike Absecon,NJ 08201 http://www.ditmire.com 609-641-3392
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I knew exactly what was wrong-- it had low compression so it would not start without the block heater. The glow plug system worked fine. I am a heavy duty diesel mechanic by trade, so I know what I am doing. I wish I could of gotten 600,000 miles out of this engine but like I said the guy at the wrecking yard was right on the money with his 250,000 mile prediction.
--Geoff
Bill Ditmire wrote:

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Eh. I have about 320K miles on mine. Still starts great.

--
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Good for you!
It's refreshing when one reads of an owner who approaches a project objectively, especially a big one like this. These engines have a 250K mile useful life and your analysis shows what actually needs to be replaced after all those miles - some valve guides and their seals and the engine's piston rings. Q.E.D.
The beauty of these 617. engines is their durability and relative simplicity.
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Only if you don't change the oil. 400-500K is more usual with good maintenance.
There are cars still running around with 700K on the original motor.
--
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http://www.mbz.org | Mailing lists: http://lists.mbz.org
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Interesting. I am willing to admit my engine would have lasted a lot longer had the intake guides not worn out-- I believe that the sloppy intake valves dancing around the seat caused a poor seal and eventually low compression. The oil was changed regularly as there was no sludge or oil deposit build up inside the engine as you normally see with ones that have not had the oil changed regularly. I wonder why the intake guides wore out?
--Geoff
"Richard J. Sexton (At work)" wrote:

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