Re-quote from an old thread because it's relevant here:
Anyway, something funny about the Oldsmobile diesels... it was more GM cost cutting that made them suck, reliability wise. Oh, and insufficient dealer training.
The original Olds diesels were, by no stretch of the imagination, good engines. (On the other hand, the 1982 DX-block Olds diesels, which had only the bore and stroke in common with the gasoline Olds 350 (and was popular for NASCAR use, with gasoline heads and pistons retrofitted, due to the heavy duty block,) were good, except the heads could've used more bolts holding them down. (And the Olds 4.3 V6 diesel had a revised head bolt pattern, that fixed THAT problem, too.) But, the damage was already done.)
However, the engines themselves were not the dreadful engines that everyone makes them out to be.
There were three critical flaws with the Oldsmobile diesels, none of them with the engine itself.
Flaw #1, the one responsible for the most engine failures: There was no water separator in the fuel system... so water would rust out the fuel injection pump's timing advance mechanism, increasing cylinder pressures above specification, causing something to let go (usually the head gasket.)
Flaw #2, usually evident after repairs from flaw #1: Dealers weren't trained sufficiently on how to repair the engines, and that the head bolts were one-time-use... so they reused them. Well, the head bolts were stretched now, and couldn't hold, and the head gaskets quickly blew again. (I'll note that VW dealer mechanics are known for doing this exact thing on various bolts on the TDIs, causing things like timing belt failures, and engines to fall out of cars.)
Flaw #3: Again, this one's a dealer training issue... dealers would often put cheap 10W40 gasser oil in, which couldn't handle the soot loading or high combustion chamber temperatures of the diesel engine. (Interestingly, it's yet another thing that VW dealers are infamous for - putting the wrong oil in cars. I've heard of dino oil in 1.8Ts, non-505.01-compliant oil in 2004+ TDIs, dino oil in TDIs, gasser oil in TDIs, etc., etc.)
There are a lot of lessons to be learned there, both in terms of design (i.e. water separator is MANDATORY) and on the maintenance side. You can see, though, that when design flaw #1 happened, design flaw #2 would pretty much guarantee that the car would be coming back to the dealer every, oh, 10, 15k for new head gaskets. And you can easily see how the owner of the car would be very unsympathetic to this, easily declaring the car/engine junk.