Problems With Duramax

by Richard Rowe
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Oh, the best laid plans of mice and men. Produced in a joint venture between long-time partners Isuzu and GM, the Duramax V-8 was a revolution in design when it first debuted -- and like many other revolutionary things, it's had a few teething problems over the years. Mechanics have gotten plenty of experience dealing with the Duramax's many known issues for different model years, because over a million have rolled out of the Moraine, Ohio plant since the engine debuted.

Fuel Starvation and Injector Problems

These two problems are thought by many to be related, though that hasn't entirely been confirmed. The Duramax has long been susceptible to fuel starvation failures because the engine doesn't use a lift pump to feed the primary pressure pump. It's common, particularly on 2001-to-2007 LB7 models, for the filter housing before the filter to develop cracks and leaks in the O-ring, allowing air to enter the system. Combined with a clogged fuel filter, this has been suggested as a cause for the rampant injector failures on 2001-to-2004 models. GM introduced a new injector design in 2005, and opted to cover injector failure and subsequent retrofit under the seven-year warranty. But even the new injectors are prone to failure, especially if contaminants make it past the fuel filter or pump.

Blown Head Gaskets

Duramax engines are known far and wide for common head gasket failures, which many have attributed to the then-controversial use of aluminum heads. However, many new diesels use aluminum heads and there's no evidence that the head design itself is to blame. Nevertheless, head gasket failures are very common, particularly on higher mileage vehicles and engines re-tuned for more power. At this point, the general consensus is that blame lay with the head bolts, which can stretch over time or with hard use. Duramax hot-rodders have found a preventative solution in the form of aftermarket, chrome-moly head studs. These have become more or less a prerequisite for any kind of performance upgrade, but then, installing stronger head studs can help any engine to ward off head gasket failure before it happens.

Cooling Issues

The Duramax's tendency to overheat is another one of those mystery problems, and one complicated by the fact that it doesn't happen to every engine. It happens most often on 2005-and-earlier engines; that year, GM started installing larger radiators, which seems to have solved the problem. Otherwise, trucks pulling the maximum 22,000-pound gross combined weight up steep grades in the summer are known to simply run out of cooling capacity. This seems unrelated to water pump failures, which are common on engines with 80,000 to 100,000 miles. Most likely, the overheating issue goes back to these engines' variable-geometry turbo, which can be more restrictive than a typical waste-gated turbo. The VGT will tend to trap exhaust gases in the engine, leading to a transient problem with heat build-up.

Glow Plugs and PCV Failure

Overheating glow plugs might not seem like that big of a deal; and they're not, until they melt and break off in your engine. This problem affects primarily 2006-model-year-engines, and is a result of the glow plug module over-cycling the plugs. Several engines have fallen to this seemingly minor issue, which is why GM created a new programming protocol for the module. If your module hasn't had this reprogramming, head down to your local dealership for the software update; they should offer it free of charge. Oil leaking through the positive crankcase ventilation tube -- that's your problem to deal with. The PCV systems on many of these engines will tend to leak oil into the intake before the turbo. The oil not only coats the turbo blades, it pools down in the intercooler. There, it eats the silicone rubber lower hose, which will eventually develop a hole and blow out.

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