Wednesday, April 6, 2011

Here's a nasty little trip down memory lane.

I was a dealership technician for several years, into the middle 'eighties. In my first dealership, being low guy on the stick, I got sent to school to learn how to service Oldsmobile diesels. Little did I imagine the horrors to follow - in the small Texas town where I wrenched, two big oil well service companies bought whole fleets of Delta 88's with the miserable things. Which meant I practically specialized in keeping them running.

From the article:
The ideal gas laws tell us that as a volume of gas is compressed, its temperature goes up, and, in the case of a diesel engine, it's compressed until the diesel fuel in the combustion chamber ignites. This leads to much higher compression ratios and combustion chamber pressures than is present in a gasoline engine. Typically, diesel engines have more and stronger head bolts to compensate for the diesel's higher cylinder. The Oldsmobile diesel, however, maintained the same 10-bolt pattern and head bolts as gasoline engines', so that common production tooling could be used for both the gasoline and diesel engines.

In the field, this proved disastrous. The insufficient head bolts stretched or broke and led to head-gasket failures. Once the head gasket was breached, coolant leaked into the cylinders, and because clearances in a diesel engine are so tight, invariably this lead to hydrolock and severe engine damage.
Yeah, that was one of the more expensive things that could go wrong, but the list of possible failures was extensive and sometimes comical. Like the fuel injector pump: A proven Roosa Master design, almost identical to a pump John Deere tractors had used for decades. Bolt them to the Oldsmobile, and the failure rate was better than 100%. Why? The pump is supposed to be liquid-cooled, sure, but on the Deere it's bolted outside the block. The brilliant Oldsmobile designers buried it inside a deep cavity in the intake manifold, with the air crossover, air filter housing and engine hood to make sure it got no air circulation at all. Then they routed the fuel line in such a way that by the time fuel actually reached the pump it was supposed to cool, it was practically ready to boil. We had infinite problems with those pumps, which took hours to swap out.

More horror stories below the fold.


The engine used a typical GM oil pump for V8s of the period, wholly inadequate. At an extended idle oil pressure dropped to something like 6 psi, which wasn't enough to lube the pot-metal brackets holding the valve rocker pairs in place. The rockers were steel, and neatly machined deep grooves for themselves into the brackets so the valves couldn't open. We used to stock those brackets by the case - every time an oil service guy wanted a day off, he just let his engine idle overnight. You could hear them coming to the shop from two blocks away.

The article mentioned hydrolock? Yeah, I saw a bunch of popped head bolts and warped heads. But the easiest way to hydrolock the engine was to simply drive the car in a hard rain. The air intake went through a conventional "flying saucer" air filter housing, which was never designed for the high airflow of a diesel. At wide-open throttle, it made the damnedest whooping noise you ever heard. To keep the complaints down, GM mounted a big plastic suppressor in the intake side of the filter housing. This was connected to a scoop on the grill through a flexible hose. Twice during the rainy season we got diesels come in the shop with hard misses. Diagnosis showed pistons that were simply...gone. They were crumbled into bits in the crankcase. We didn't know what caused it - we just swapped out the short blocks under warranty. Then we got one of those quiet "all cases" TSB's GM liked to issue back then. On all diesels, regardless of complaint, we were to take off that big plastic suppressor, turn them upside-down, drill a bunch of holes in the bottom and re-mount them. It seems they were filling with water. When they got full enough, whichever lucky cylinder happened to be on an intake stroke when water sloshed into the air filter was doomed. At top dead center, there was virtually no space between the piston and the cylinder head. Water's a little hard to compress, and something had to go. The engine didn't actually hydrolock, as a rule: The piston shattered.

Ah, the Oldsmobile 5.7L diesel. The stories I could tell. They quite ruined my career as a dealership technician: I spent so much time working on them that the first couple of generations of electronic engine controls passed me by and I was way behind the times. Ironically, in later years I specialized in powertrain controls as a trainer and tech writer. So in a way, I suppose you could say the diesels led me to a better career. Sweartagod, I used to dream about those horrible things.

9 comments:

Claire said...

I remember your Oldsmobile diesel horror stories from my days as your neighbor, Joel.

When I clicked on the article I was shocked -- simply shocked -- to discover that government regulations led to the introduction of such badness.

wrm said...

Government regulations having unintended consequences? Never! I too am shocked.

W

Joel said...

Oh, hell yes. I always said the 5.7l Diesel was designed in a board room. The article's explanation varies somewhat from the one I heard, which was that adding a diesel to the line would bring GM's Corporate Average Fuel Economy into federal compliance and they didn't want to go to the trouble of designing a real one. But close enough either way.

Tam said...

Ah, the Olds diesel... Perhaps Detroit's lowest ebb. (And from the company that brought us the V-4-6-8, the Aztek, and the Volt, that's saying a lot...)

WV: "nolikers" Yes, the Olds 350 diesel has no likers.

Anonymous said...

Two jobs ago, they bought a couple as part of the fleet vehicles-as I recall, they had a bout a 30,000 mile life. The Olds wound up having a couple old 305s(or 350s-I wasn't involved with it,really) just sort of sitting around put in them,and the diesels went with the next load of scrap iron.
Also, it seems they were difficult to impossible to start if the temps dropped below freezing,and were cranky at fifty degrees.

MamaLiberty said...

Job security for the automaker and parts suppliers... if the customer can be forced (or is stupid enough) to buy it.

Seems to work rather well in all sorts of industries these days.

Ken said...

Yep, the Olds 5.7 diesel is one of my "don't be that guy" case studies I use in class.

Curiously, rather a lot of those cases involve GM one way or another....

Bustednuckles said...

Fucking engineers. I hate 'em.
I feel your pain, I was a Lincoln/Mercury tech, college trained, for ten years.
I wanted to strangle some of those assholes with my bare hands.
Reading this post makes me wonder why you are having so much trouble with that damn tractor, must be something unusual.
I did get a chance to show some hot shot engineer from Ford what a dumbass he was once.
The air intake at the bottom of the windshield for the heater-A/C system was a huge oval and up here it can rain an inch in ten minutes, the water drain was less than a half inch. Constantly getting forty thousand dollar cars with wet carpets because the heater box got full of water.
I nailed him but good for that one

They should make those guys work on the shit they design for a month straight.

Joel said...

Bustednuckles,

There's no mystery about my travails with the tractor. It's very old, I need to get my parts from hundreds of miles away, and I was pretty much alone here through the winter. Also, I'm no diesel mechanic. I used to be a pretty fair auto mechanic, but my time in the dealerships ended almost thirty years ago. I'm really not a wrench anymore. So I'm still learning on the tractor.