Quote:
Originally Posted by srmmmm
The disappointment with the 5.7L Olds diesel was the damage done by the first generation clouded perception of the second generation. The first suffering from severe lifter and cam lobe wear from oil contamination. Owners did not realize the importance of the 3000 mile oil change with the diesels compared to lazier practices with gasoline engines. The EGR system in the diesel pumped a lot of soot back into the crankcase as blow-by. Additionally, the lack of a water separator contributed heavily to those blown head gasket situations as well as injector pump corrosion.
I had a 1981 Bonneville with the second generation 5.7L diesel and had no problems except for a fuel gel-over during the big chill in 1983 until about 70,000 miles. One of my GMI classmates worked on the V-6 diesel development at Oldsmobile and and gave me a few tips on the 5.7L for reliability. The roller lifters in that engine cured the cam wear and a water separator had been added in the fuel filter. My problem was worn out wrist pin bushings leading to piston slap and three bent rods.
I found a specialist in OKC that rebuilt them with drilled rods to pressure feed the wrist pin bushing, and he changed the head bolts to the larger diameter ones from the 6.2L diesel. He essentially blueprinted the engine and you could definitely tell the difference with the ease of starting and performance gains. I went another 200,000 miles on the engine before a Texas hailstorm totaled out the car. I never got less than 22 mpg with that car and went as high as 34 mpg on the highway.
My biggest complaint was the wimpy Turbo 200N transmission they used. I went through 4 rebuilds due to lock-up torque converter failures. The diesel had too much torque at low rpms before the transmission oil pump pressure was high enough to maintain the lock-up in the converter.
Still the best long distance cruiser I ever had though.
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I also had a 81 diesel Bonneville, 4 dr white with maroon cloth interior, factory red pinstripe. I bought it at 48,000 and drove it to 150,000 with zero engine problems. The guy I sold it to absolutely refused to buy it with a diesel engine. so I converted it to a 350 rocket gas engine. I sold the 5.7 engine running, and never heard anything from the guy that bought it from me. I assume it ran fine after he installed it.
At that time I was working as a line mechanic at a buick dealership, and was privy to all the missed maintenance items that got overlooked when diesels were serviced. One main problem was the valve cover breather filters never got replaced, or even washed out at oil changes. Carbon plugged up the inadequate gas engine breathers, and then blowby had no where to go with the plugged breathers. It blew out the rear main seal from too much crankcase pressure. As well as the RTV valve cover seal, no gasket, creating massive oil leaks. letting owners finally run the engine out of oil and causing crank and bearing failures, called reliability problems.
As it has been already pointed out, an outstanding car for highway trips. Great comfort as well as great mileage, and at that time diesel fuel was still less than gasoline per gallon. Properly maintained the second gen 5.7 was a fair engine, not great, but adequate in my experience. As the article said from 77-80, they were ticking time bombs.
After installing a few 5.7s in pickup trucks GM wisely called upon Detroit Diesel to design the 6.2/6.5 engines for light duty trucks, but they too had some problems from design shortcomings, and penny pinching book keepers. IH/Navistar took on the manufacturing of the 6.5 diesels after GM dumped the design for the Duramax to keep making it for the military for the military Hummers. The IH/Navistar 6.5, is a much improved quality piece over the same GM offerings previously. The Hummer late model government surplus 6.5s are highly sought after as replacement engines for civilian GM light duty trucks. They are a much better built rendition than what GM was making.
If the post 1980 diesels were properly maintained, they ran well and got great fuel mileage. In 1985 I drove mine from Erie PA to Phoenix AZ, and best tank was 32 MPG. Hard to argue that mileage in a full size car when the same gas powered car would likely never see 20MPG. My TH 200 never gave up when I had the diesel. When I put the gas engine in, I left the TH 350 bolted to the rocket 350, so the car had a durable transmission when I sold it. Unfortunately the guy that bought it pulled onto the highway in front of another car, and totaled it about a year after he bought it. My injection pump finally went out at over 130,000 miles, and I just bought a used one for it from a friend that owned a wrecking yard. At the time a reman was in the neighborhood of $550, lots of money in the late 80s.
Just like the corvair, and the Fiero, GM finally got the cars/engines figured out and working, just before they went out of production due to the bad rap from the earliest models. In the corvairs case, Ralph Nader hastened their demise. Funny too that the IRS 61-63 Tempest used the basically same swing arm rear suspension as the corvair did, as did the VW bugs, but no mention of either of those cars having the same ill handling type of suspension quirks. There were probably other cars that used swing arm rear IRS that I'm forgetting about during that time.
GM was famous for doing field testing of new ideas, and making the customers the Guinea pigs. Denying that their designs/ideas were just fine, even though customer complaints proved otherwise. When they dropped Pontiac, I never bought another new car from GM, and never will either.
