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Diesel-powered pickup trucks are desirable because they tend to make more torque and waste less energy than a comparable gasoline-powered model. Diesel engines are also supposed to have an exceptionally long service life—but that doesn’t mean they can’t suffer from pattern failures. 

Although there have always been troublesome diesel engines (for example, General Motors’ 5.7L diesel from the 1980s), modern diesel-powered vehicles now have the added complexity of electronics and emissions equipment that can create a distinct set of problems. 

In some cases, these newer diesel-powered trucks suffer from pattern failures that affect thousands of examples. Below, you’ll find some of the most infamous problems that are known to affect today’s diesel vehicles.

Eight Pattern Diesel Truck Failures From Different Manufacturers 

Every automaker and engine manufacturer has produced multiple design flaws and manufacturing defects over the years. Let’s take a look at some of the most common, high-dollar pattern diesel truck failures that you might come across.

Note: Although the failures on this list are common, they don’t always happen. Only a certain number of vehicles are actually affected by each design flaw or defect.

Power Stroke 6.0L Torque to Yield Bolts and Head Gasket Failure

The 6.0L Power Stroke engine—a joint venture between Navistar International and Ford—debuted in the 2003 Super Duty as a replacement for the outgoing 7.3L. Since the 6.0L engine was introduced, it has had a reputation for being exceptionally troublesome. 

Although the 6.0L offered a significant performance gain over its predecessor, it was also riddled with many common problems. One of the most well-documented issues is the engine’s weak torque to yield (TTY) cylinder head bolts.

Many vehicles use TTY bolts (a type of fastener designed to stretch slightly) without any issues. The problem is that the 6.0L doesn’t have enough bolts to provide the clamping force needed to keep the cylinder heads flush with the engine block. As a result, the cylinder heads often lift away from the engine, allowing combustion gases to sneak past the head gasket and into the cooling system, causing overheating and other issues.  

The end result is (at minimum) a costly head gasket replacement that requires approximately 20 hours of labor and often costs upwards of $5,000. Most repair facilities choose to remove the truck’s cab from the chassis to complete the job since that’s often the easiest route to repair. 

Power Stroke 6.0L Exhaust Gas Recirculation (EGR) Cooler Failure 

Exhaust gas recirculation (EGR) technology reintroduces a metered amount of exhaust gases into the engine to limit combustion temperatures, thereby reducing the production of harmful nitrogen oxides (NOx). Even though gasoline-powered vehicles have had EGR systems since the 1970s, the technology didn’t become commonplace on diesel engines until the early 2000s.

Diesel engines often use an EGR cooler to reduce the temperature of the EGR gases before they enter the engine’s intake. Engine coolant flowing through the cooler acts as a heat transfer medium to absorb heat from the exhaust.

An EGR cooler sounds like a good idea (and it usually is), but the cooler on later versions (‘04-’07) of the 6.0L Power Stroke engine has a restrictive rectangular design that inhibits coolant flow. Furthermore, the 6.0L is known to suffer from a clogged oil cooler, which is located downstream from the EGR cooler, that can reduce coolant flow.

The subsequent increase in internal temperatures tends to cause the cooler to rupture, resulting in coolant loss, white smoke (steam) from the exhaust, and other problems. 

Power Stroke 6.4L Oil Dilution and Cylinder Washing

In 2008, Ford introduced the 6.4L Power Stroke engine as a much-needed and much-improved replacement for the outgoing 6.0L. One noteworthy feature of 6.4L-equipped trucks was that they came with a diesel particulate filter (DPF)—an emissions control device that Ford had not used on any prior production vehicle.

The DPF is designed to trap particulate matter (soot) traveling through the exhaust system. DPF-equipped vehicles must periodically go through a process called regeneration to prevent the filter from getting clogged.

Sometimes, the engine management system must introduce a select amount of fuel into the exhaust system to perform active regeneration. The fuel raises the temperature of the exhaust, causing the particulate matter to ignite and burn.

While some vehicles have a dedicated injector (vaporizer) in the exhaust stream for regeneration, the 6.4L introduces fuel into the exhaust via a post-injection strategy. The method injects fuel into the engine’s cylinders (towards the end of the exhaust stroke) to introduce fuel into the exhaust system.

The problem with this post-injection strategy is that it allows some fuel to stick to the engine’s cylinder walls. That fuel can eventually sneak past the piston rings and into the crankcase, causing oil dilution.

Because fuel-diluted oil doesn’t lubricate well, the engine can suffer accelerated wear, especially if the oil isn’t changed frequently. Post-injection also tends to wash the cylinders of their protective layer of oil, which can decrease engine life.

Duramax 6.6L LB7 Injector Failure

In 2001, General Motors (GM) introduced its first Duramax engine (code-named LB7) into its lineup of heavy-duty trucks. The 6.6L Duramax LB7—a joint venture between GM and Isuzu—replaced the 6.5L Detroit diesel previously found in GM vehicles.

While the LB7 is a stout engine, its fuel system leaves something to be desired. Fuel injector failure is widespread on the LB7—so much so, in fact, that GM released a special service campaign (# 04039C) to address the issue.

The campaign extends the warranty on the LB7’s injectors up to 7 years or 200,000 miles. Unfortunately, many trucks experience repeat failures, leaving customers having to pay for a second (or third) round of injectors out of pocket. 

There are a variety of speculations as to why the LB7’s injectors fail so often. One potential cause is that the internal ball seat inside of the injector is not hardened, resulting in erosion and premature failure. Contaminated fuel and lack of fuel system maintenance could also be contributing factors.

Replacing the injectors isn’t cheap, either. On average, the repair costs between $4,000 and $5,000 for a shop to complete. The job typically requires 10 to 12 hours of labor, and the injectors cost around $350 each. 

Duramax 6.6L LLY Engine Overheating and Head Gasket Failure

GM introduced the second-generation Duramax 6.6L engine (code-named LLY) in 2005. LLY-equipped trucks were the first from GM to have a full lineup of modern emissions equipment, including an EGR cooler.

Although the cooler was necessary to comply with emission standards, it can cause problems, primarily because GM didn’t upgrade the engine’s cooling system to compensate for the addition. The LLY also have what some believe to be an abnormally small air intake elbow, which restricts airflow into the turbocharger, causing the unit to have to work extra hard. Consequently, the engine can overheat when taxed with a heavy load (e.g, towing up a steep grade on a hot day). 

In addition, the LLY tends to suffer from head gasket failures. Some of those failures are undoubtedly the result of the poor cooling system design and subsequent overheating. But there also seems to be an inherent design flaw in the head gasket itself, as is indicated in technical service bulletin (06-06-01-006C), which introduces an updated head gasket and replacement procedure.

Initially, GM refused to cover engine overheating as a warranty item, but the automaker changed course after facing legal challenges from a consumer group.

Cummins 5.9L 24V Lift Pump Failure

Cummins brand engines are well-known for their dependability, both in pickups and semi-trucks. In 1989, Dodge (now Ram trucks) introduced a 12 valve (12V) version of the 5.9L Cummins engine in its lineup of heavy-duty pickup trucks. The engine remained essentially unchanged until a 24V version was implemented in 1998. 

The 5.9L is still considered to be one of the best engines ever made. But the fuel system that accompanies the engine is a different story. Dodge trucks built from 1998-2007 are known to suffer from lift pump (transfer pump) failures, with models made between 1998 to 2004 tending to be the most problematic due to the pump’s location at the engine.

The lift pump is the low-pressure pump that moves fuel from the tank to the high-pressure injection pump at the engine. Not only can a faulty lift pump leave you stranded, but the problem can also starve the system of the fuel it needs for lubrication, causing an internal failure of the high-pressure pump. What’s more, when the high-pressure pump fails, metal debris often ends up circulating throughout the fuel system. As a result, the entire fuel system may need to be serviced or replaced.

Cummins 5.9L 24V Cracked Engine Block

If you’re in the market for a 1998-2001 Cummins-powered truck, you might want to take a look at the engine block before you make a purchase. Engines with a number 53 cast into the side of the block tend to have abnormally thin water jacket walls that are known to crack. When that happens, a costly ($10,000 or more) engine replacement is the usual course of repair.

The number 53 blocks were built by a Brazilian company called TUPY. Supposedly, around 100,000 of the blocks were produced, though some of them were installed in applications other than pickup trucks. 

A class-action lawsuit regarding the blocks was settled in 2011, awarding owners of affected vehicles up to $500. Unfortunately, an engine replacement can cost twenty times that amount. 

Power Stroke 6.7L, Duramax 6.6L LML, and Cummins 6.7L High-Pressure Injection Pump Failure

Most modern diesel-powered trucks have a common rail fuel system. The design relies on an engine-driven, high-pressure pump to pressurize fuel that’s delivered to computer-controlled injectors. 

One example of a common-rail high-pressure injection pump is the CP4, manufactured by Bosch. The CP4 is used in Power Stroke 6.7L (2011-present), Duramax 6.6L (2011-2016), and Cummins 6.7L (2019-present) engines.

Over the years, the CP4 has been the subject of many lawsuits because the pump tends to come apart, contaminating the fuel system with metal. When that happens, the entire fuel system usually needs to be serviced or replaced, which can generally cost anywhere from $8,000 to $20,000.

Most lawsuits claim that the pump is “incompatible” with the clean (low-sulfur) diesel fuel found in the united states. Separate lawsuits have been filed for CP4-equipped Power Stroke,  Duramax, and Cummins engines. Stellantis (formerly Fiat-Chrysler) recently recalled more than 246,000 Ram Heavy Duty trucks to replace the CP4 pumps.

How Can You Avoid a Diesel Truck Failure?

Today’s diesel-powered trucks are incredibly complex and can cost a small fortune to repair. If you want to avoid an expensive breakdown, it helps to do your homework on whatever model you’re considering buying before you make a purchase. 

It’s also important to avoid vehicles that have been tuned (or modified for power in any other way). Diesel tuning alters the engine management system to adjust operating parameters, such as fuel delivery and boost control, to make more power. While the modification is a relatively easy and inexpensive way to improve performance, it puts additional strain on the engine and powertrain.

Although modifications certainly don’t account for all modern diesel engine failures, they can (and often do) play a role, as the video below demonstrates:

Routine maintenance is also of utmost importance on diesel-powered vehicles. You’ll want to keep up on fluid exchanges, filter replacements, and all other services recommended by the vehicle manufacturer. Purchasing your fuel from a reputable filling station is also important, as it limits the possibility of getting contaminated fuel. 

Hopefully, if you follow these strategies, you’ll have a diesel-powered truck that continues to run strong for a very, very long time.

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