Part 1: GMC/Chevrolet

Published in the September 2013 Issue September 2013 News Michael Deulley

We've all had occasional issues with our truck. Every now and then, we're forced to replace a worn-out suspension, a bald tire, a fuel filter that's functioned far beyond its intended life cycle, just to name a few. But for every truck, there are bugs inherent in the system that could unavoidably force flustered owners to spend money that they never intended on throwing into repairs. Diesel Tech magazine has teamed up with Erik Lind, owner of Left Coast Diesel, in Livermore and Concord, Calif., and his crew to give you the low-down on the possible issues you could inevitably face with your truck and give you information that can help you make a better decision when buying used. Over the next three issues, we'll explore inherent issues in GMC, Dodge and Ford trucks that you may not have heard about, but will be glad to know. In this feature, we'll focus on GMC and Chevy trucks, with special interest in their engines.

The Duramax Engine

From 2001 to 2011, the Duramax engine has had a similar configuration, and with that, similar issues. According to Lind, there are common issues with the engine becoming starved for fuel. Because there is no factory lift pump to circulate fuel, the injection pump has to suck fuel from the tank and through the filter to run. This doesn't immediately cause fuel issues, but eventually, with dirty or loose fuel filters, leaking water-in-fuel sensors or bad o-rings in the fuel filter housing, the truck can experience no-start conditions.

Along with general fuel issues, there are several common failure items strewn throughout the truck that must be taken into account. The water pumps become an issue over time, and are generally in need of replacement after 100K miles of use. Having two discretely placed weep holes—which are hard to see and easily overlooked—the pumps are hard to monitor and are even harder to replace when they finally give way. Another thing to keep an eye on is the front wheel hub assembly. Being another one of Lind's common failure items, they become ever more prone to failing if the stock tires are swapped out for larger ones, or if the truck spends a lot of time off-road. Tie-rod assemblies are proven to be notoriously weak, according to Lind, and will often snap if excessive force is exerted on them, especially during four-wheel drive launch. Lastly, in our general overview of GMC and Chevy systems is the idler and pitman arms. The design of Chevy and GM’s steering linkage allows side-loading of the idler and pitman arms, causing them to wear out and perform poorly.

These are just a few issues that Chevy and GMC platforms may face throughout their lifetime, but Lind commented that there are many great aftermarket parts that rectify these issues and save owners a lot of time and even more money in the future.

Now that the general Duramax system issues have been addressed, we'll focus on more specific problems that Lind and the Left Coast Diesel crew has become familiar with over the years.

LB7 Platforms

The LB7 (2001-2004) has gained notoriety for its less than satisfactory fuel injector issues. The injectors seemingly have chronic premature failure, which has led to warranty extension and a rush for Bosch to redesign and create better-performing aftermarket injectors.

“The injectors tend to have a high return rate, which can kill performance and actually put the truck into limp-home mode,” says Lind. “They also develop leaks through the nozzle, which will show up as smoke and haze while at idle. Extreme failure can result in holes in pistons. If one of these conditions is noted, all eight injectors must be replaced. The real downside to the LB7 trucks is that they are the most labor-intensive injectors to do, taking about 13 hours.”

Lind also noted that the fuel filter housings are often susceptible to premature failure, and are also the most expensive housing to replace.

LLY and LBZ Platforms

Along with having many of the same issues as the LB7, the LLY (2005 to early 2007) and LBZ (2007) also face a new set of possible untimely issues. Head gaskets have a tendency to fail early on, causing the heads to shift, which, if you've ever experienced a cracked head gasket, or other head problems, cause massive problems which must be repaired immediately. Every LLY and LBZ that Lind has come across has also had consistent issues with water pumps failing, and the CP3 injection pump failing anywhere from 175-200K miles, which is a reasonable, but still an expensive repair to prepare for.

Lind and the team at Left Coast Diesel have also seen consistent problems with trucks equipped with EGR systems.

“All of these smog trucks that have EGR systems are prone to failures in the vacuum pumps,” says Lind. “The pressure drops lower than specifications and shows up as a P0404 code. Drivers also experience idle fluctuations and lower power. Sometimes, the pump will 'clack' on the passenger side, but can sometimes be completely quiet, which is even more dangerous and very difficult to diagnose.”

Lastly, Lind has noticed failures in either the glow plug module or the glow plugs themselves. The truck will send an O3E P0380 code if one of the glow plugs has gone bad, but will also give this code if the module itself has failed. Lind suggests that LLY and LBZ Duramax owners check each glow plug before swapping out the module.

2004-Present Platforms

Although GMC has worked to remedy the problems that the Duramax engine has experienced through the years, the newer platforms still face common issues inherent within its predecessors. Lind has suggested that owners take the time to examine the entire system before making any decisions on the necessary repairs, and become educated on how the system works before taking the truck to a shop.

Some of these issues are devious and may show up as one problem, but could be something else entirely. Duramax drivers should always be on the lookout for these common problems, and address any issue—no matter how insignificant it may seem—as soon as possible. Taking care of the minor details could be the difference between a small expenditure and a serious financial investment.


Editor’s Note: The Troubleshooting feature is a three-part series that focuses on the top three diesel truck manufacturers. Part two in our next issue will look at the Dodge Cummins engine.   

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