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The Sad Story of the American Diesel Engine
The return of the diesel engine to North America is on everybody’s lips these days. Of course, diesel was never completely absent from our market, but its popularity has had its ups and downs over the years. An object of curiosity in the 60s (only Peugeot and Mercedes offered diesel back then), these engines became more common in the late 70s with the arrival of diesel from Volkswagen, Oldsmobile and Volvo (which had a VW engine). Everybody got on the diesel bandwagon after that, including BMW, Ford, Chevrolet, Nissan-Datsun and Toyota. Diesel became ubiquitous: from the diminutive Chevrolet Chevette (with an Ìsuzu engine) to the Toyota 4×4 Land Cruiser, luxury Lincoln MK IV (with BMW engine) and Nissan Maxima.
But why didn’t diesel stay popular after that? Many reasons can explain its drop in popularity: cheap fuel, for one thing, as well as diesel’s limited performances, its disagreeable smell, and the exhaust fumes (problems TDI technology has solved). But the main reason, especially in the United States, was the repeated failures of the diesel V8 made by Oldsmobile. There’s nothing worse for a reputation than a lack of reliability at the very heart of a car.
Let’s take a closer look at how a single engine (a huge 5.7 litre V8 with only 120 hp and 220 lb-ft of torque, which is less that the present 2.0L TDI) was able to do so much damage to the reputation of Rudolf Diesel’s invention.
The design
Although based on the gas engine (the famous 350R Rocket), the Oldsmobile diesel was extensively modified and in keeping with contemporary standards of component solidity: crankshaft, connecting rod and cylinder heads were specifically designed for diesel and much more solidly built than those of a gas engine. However, GM made several design errors of secondary components like the fuel tank, lubrication system, valve movement, gaskets and head bolts.
Constant breakdowns
The main cause of breakdowns was a vulnerable cylinder head gasket attached by bolts that weren’t strong enough to withstand the high pressures required by diesel engines. The bolts quickly weakened, the gasket leaked, and antifreeze thus found its way inside the cylinder head or in the oil pan. With oil thus contaminated, the crankshaft quickly wore out –expensive refurbishment was then required.
If liquid leaked and filled a combustion chamber, during the night, for example, starting the engine in the morning would just serve to prove that liquids are incompressible. The powerful starter would turn the engine, and the liquid would prevent the piston from completing its cycle (because the small combustion chamber was filled with liquid): something had to give. Usually, that something was a connecting rod or the crankshaft. They would fracture and require the engine to be replaced.
In the lucky cases where the leak was not destructive, another problem arose when the cylinder heads had to be reassembled. The bolts used to secure the heads were of the stretch-to-yield type, i.e. single-use bolts designed to distort during tightening for greater strength. You see the problem? Mechanics who didn’t know these bolts had to be thrown out would reuse them, making the gaskets even more fragile because of a lack of pressure. Breakdowns were thus all the more frequent.
Water in the fuel
Another recurring problem was the inexplicable absence of a water separator in the fuel tank. Diesel engines are very sensitive to the presence of any water in the fuel, since this causes corrosion of the injection pump, dephases fuel injection, and causes the gasket to break, which brings us back to the problem mentioned above. GM corrected the problem with a 3-gallon water separator in the fuel tank. That gives you an idea of the water that was present in diesel fuel at the time.
Consumers were also partly responsible for some breakdowns, some using fuel line antifreeze that, because it contains alcohol, attacked the internal parts of the injection pump. This caused dephasing of injection and gasket leaks, which lead to you know what.
If the engines managed to avoid all these problems, they still had to face certain mechanics who didn’t know about diesels requiring a specific type of motor oil. Using regular oil caused medium-term damage to the crankshaft and, if the oil wasn’t changed often enough, to valve lifters. More cylinder head replacements, more bolts replaced, more breakdowns.
All the above problems have been documented and resolved. At the time, however, when many consumers were abandoning their gas V8s to adopt diesel V8s, all these problems did serious harm to diesel’s reputation in the United States. Many American swore they would never be “taken” again.
Nearly 30 years later, diesel is entering a new era thanks to clean diesel. Let’s hope that everyone has done their homework this time.
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