DailyReview: Cadillac's Trinity of Trouble?

[Bruce Nunnally]

Hi Greg. I really enjoy your answers to reader's questions, so I'm throwing my two cents in. I know you like Cadillacs and that you've owned a few yourself. How about telling us when you feel were the worst years for Cadillac during your years, be it sales or development?

Read more: http://thedailyreview.com/sports/car-collector-corner-cadillac-s-trinity-of-trouble-1.1702570

Although this is a popular criticism of the diesels, I believe the actual issue was sensitivity of the engine to the quality of the diesel fuel of the time.

The 8/6/4 system, by Eaton, worked and is a technology back in use today. The base 368 v8 engine was quite sound if underpowered by today's standard.

My Mom had and enjoyed a Cimmarron, which by the final V6 iteration was a nice economy Cadillac.

Overall I agree however that issues with the diesel followed by issues with the replacement HT4100 and poor choices in Cadillac Customer service were deadly for the brand's image. The HT4100 evolved into the 4.5l and 4.9l v8s which are nice, reliable engines.

[Cadillac Jim]

My wife had a 1990 Sunbird convertible and drove it for years. It was an excellent car. That was sometime after the Cimarron, and the platform may have changed, but it was solid, even in a convertible, and handled well.

[KHE]

A little misinformation in the article. The Oldsmobile Diesel was NOT a gasoline engine that was converted to run on diesel fuel.

Also, the V8-6-4 was only available for the 1981 model year for the Eldorado, Seville, Fleetwood, and Deville. From 1982-1984 or 1985, it was only used in the limousines.

A lot of people use 20/20 hindsight to be so critical of Cadillac but in those days, they had to do whatever it took in order to meet the government regulations. The V8-6-4 was almost 30 years ahead of its time. The V8-6-4 was intended to be used through the 1983 model year untill the FWD cars were released for the 1984 model year but issues prevented the FWD cars from being released until the 1985 model year (fall, 1984) so they carried ofer the RWD cars for one additional year. The HT4100 was then used in the RWD cars due to the issues with the V8-6-4 engine. From what I understand, it was a hardware issue in the ECM that caused the issues with the 8-6-4. Most people had the feature disabled if it gave them problems - the 368 engine was a rock solid engine.

[Texas Jim]

Hi Greg. I really enjoy your answers to reader's questions, so I'm throwing my two cents in. I know you like Cadillacs and that you've owned a few yourself. How about telling us when you feel were the worst years for Cadillac during your years, be it sales or development?

Read more: http://thedailyreview.com/sports/car-collector-corner-cadillac-s-trinity-of-trouble-1.1702570

Although this is a popular criticism of the diesels, I believe the actual issue was sensitivity of the engine to the quality of the diesel fuel of the time.

The 8/6/4 system, by Eaton, worked and is a technology back in use today. The base 368 v8 engine was quite sound if underpowered by today's standard.

My Mom had and enjoyed a Cimmarron, which by the final V6 iteration was a nice economy Cadillac.

Overall I agree however that issues with the diesel followed by issues with the replacement HT4100 and poor choices in Cadillac Customer service were deadly for the brand's image. The HT4100 evolved into the 4.5l and 4.9l v8s which are nice, reliable engines.

I had three diesel GM cars...1980 Oldsmobile 98, 1981 Seville, and 1981 Sedan deVille.

I think the main problem with them was that the CONSUMERS did not know that regular 30 weight oil was different than diesel oil.

I used the same diesel oil that I used in my big trucks and I never had a minutes trouble out of any of them.

I also drained the water out of the fuel filters every week or so.

The exhaust system on the diesel cars SUCKED... and that's being VERY polite... LOL

When new, they smoked really bad, but that could be fixed.

You had to replace the little bitty single exhaust that came on them with a much larger, true dual exhaust and an "X" pipe.

Then you took it and had the pump turned up.

Then they performed about equal to the stock 350 gas engines of the day, but got at least twice the mileage of the gas engines.

And they no longer smoked very much at all.

I was very happy with mine.

The '81 Seville was Darling Wife's car.

I sold the Oldsmobile to a friend and he drove it for 3 or 4 years.

[KHE]

The single biggest killer of the Oldsmobile Diesel was owners using 10W-40 oil instead of straight 30 weight diesel oil. The 10W-40 would cause the rings to stick and the engine would lose compression. 30 weight diesel oil was only available in truck stops in those days, not at K-mart, etc. Of course, it was always the engine's fault when they lost compression...

Another killer was owners using either to get them started in cold climates instead of plugging in the block heater at night.

[Texas Jim]

The single biggest killer of the Oldsmobile Diesel was owners using 10W-40 oil instead of straight 30 weight diesel oil. The 10W-40 would cause the rings to stick and the engine would lose compression. 30 weight diesel oil was only available in truck stops in those days, not at K-mart, etc. Of course, it was always the engine's fault when they lost compression...

Another killer was owners using either to get them started in cold climates instead of plugging in the block heater at night.

Way back then, I used RPM DELO 40w in the summer... 30w in the winter.

Down here in Texas, we didn't need a block heater... but it did take a good bit longer in the winter, before the glow plug light would go off...LOL

[Cadillac Jim]

There are people who will buy a new car, drive it for two years without even an oil change, and trade it in. In the 1980's that seemed to be the rule more than the exception. The Vega's high-silicon aluminum bore was just fine so long as you kept the oil changed, but...

Well, that same high-silicon aluminum bore technology was great in the 495 that the Chaparrals ran, along with lots of top fuel dragsters and many, many marine applications - and a few 800 hp aircraft engines.

So, given the right oil and draining the water out of the fuel separator once a week made the GM V8 Diesel reliable, and an aftermarket exhaust made it a fine engine. That's what I've heard for years, but not in the explicit detail that Texas Jim provides us here.

[PAUL T]

We still have about an 81 Olds 98 diesel. It got 32 mpg on trips and we loved it. It did go through a few torque converters though. The engine finally went and we contemplated puting in another diesel but it never happened. It is a yard ornament now at my father-in-laws.