Duramax Years to Avoid: The Most Common Problems | REVISION (2023)

A diesel powered truck makes sense when you need a vehicle with a lot of versatility and performance. The number of diesel vehicles sold in the United States has increased by 28%, and most of these engines come from General Motors, one of the most popular diesel vehicle manufacturers.

The Duramax diesel engine is one of the main engines in a General Motor (GM) truck. While these engines are reliable and durable, some model years have specific issues that you want to avoid.

This article provides detailed information aboutduramax years to avoidfor the best Duramax model years you can buy, and also provides answers to related questions.

The most common problems with Duramax

There are several problems related to the Duramax engine. These problems are usually associated with the fuel injector, fuel injector harness wiring, water pump, engine overheating, and blown head gaskets, etc. We will address these questions one by one below.

Duramax injector failure

This problem is common on model years LB7 Duramax. Although General Motors recalled these engines and warranted them for seven years and 200,000 miles, the fuel injector was still a major problem. The exact problem with the injectors is that they were running under the valve covers.

If there are diesel leaks, the oil supply will be diluted and lead to main bearing failure. The revamped version of the LLY released in 2004 had externally located fuel injectors. This was an advantage as it made injector maintenance much easier and allowed for easy visual inspection.


Glow plugs heat the fuel and air to improve your engine's combustion efficiency. When glow plugs begin to fail, problems such as reduced fuel efficiency can arise. Your truck may also have idling, misfiring, or starting issues. Your exhaust can give off certain signals that could indicate this issue. If your exhaust assumes it's white or black instead of the normally thin and gray color, you may have a glow plug problem coming on.

While not all Duramax models have glow plug issues, if you have a 2006 model beware. The 2006 LBZ and LLY models are notorious for their glow plug issues, which led GM to pull them.

fuel system

While most known Duramax issues affect specific model years, the faulty fuel system is an issue that affects all model years. It typically starts with a vehicle that is difficult to start and then progresses to excessive smoke, poor fuel economy, slower RPMs, loss of engine power and excessive noise.

While there are several issues with the fuel system, the Duramax 6.6 liter is known to have two consistent issues. First, the 6.6 liter Duramax uses an injection pump instead of a suction pump, which can lead to cracks in the fuel filter housing. Second, the way the engine is designed allows air to quickly enter the fuel lines, preventing enough fuel from reaching the engine.

water pump

Water pumps wear out based on how long the vehicle has been driven. You can expect to drive an average diesel engine up to 100,000 miles or more before you worry about replacing the water pump. Unfortunately, when operating a Duramax engine after approximately 80,000 miles, the water pump may need to be replaced.

Some new drivers may need help understanding why a water pump should be so important. However, a bad water pump indicates that your engine is not getting enough coolant, causing it to overheat. An overheating engine is a nightmare no driver wants and you would have to stop the vehicle as many times as it overheats to let it cool down.

Overheating can lead to serious problems such as damaged cylinders or pistons, cracked engine blocks and blown head gaskets. Knowing that your Duramax engine is prone to water pump failure, you should look for potential problems.

You should have your cooling system checked by a trusted mechanic if you notice overheating, coolant leaks, signs of water pump corrosion, or howling noises from the front of the engine.

fuel injector harness wiring

This issue is common on LB7, LLY and later models. This affects the wires in the fuel injector harness system which wear out and cause open or short circuits. When this problem occurs, your vehicle may experience symptoms such as running erratically or not starting at all.

Certain injectors affected by this issue will often generate an "open circuit" code. Running the wires to a single injector may allow them to work properly for a while; this can be useful when you need to make a quick diagnosis. You can fix this by reconnecting or isolating the affected wires.


Oil problems are never a good thing, and in the case of the Duramax, the problems extend to the turbocharger. In general, when you think of oil leaks, you only think of engine oil leaks. There's a more critical issue with the 6.6-litre Duramax in particular. The oil seeps into the turbocharger and coats its internal and external components.

The problem is caused by a faulty PCV design - a properly functioning PCV should emit exhaust from the crankshaft and keep out other gases. However, this is not the case, as Duramax's faulty PCV design does the exact opposite, drawing oil into the turbocharger. This can lead to more serious engine damage that would require expensive repairs.

What years of Duramax to avoid?

Duramax Years to Avoid: The Most Common Problems | REVISION (1)

There are great models of Duramax engines to try out. However, there are certain model years that you should avoid. Below we give an overview of these years to avoid.

Duramax LB7: model years 2001-2004

As the first Duramax model to be released, the LB7 remains very popular with diesel enthusiasts due to its lack of emission control parts. In general it is a very reliable and durable engine; However, when the first model hits the 100,000 mile mark, some problems start to arise. Injector failure was common on the LB7 engine.

GM recognized the problem and eventually adapted the original design and offered a 200,000-mile warranty on upgraded Duramax parts. When buying a used LB7 it is important to know that it still has the factory installed injectors. If so, you know you have backup work to do in the future.

Other critical issues expected in the LB7 include the following:

  • Leaking fuel filter housing O-rings
  • the water pump is leaking
  • overheating
  • Head gasket failure
  • The lack of a factory lift pump.

Duramax LLY: Modelljahre 2004,5–2006

GM only produced the Duramax LLY engine for a short time. It was almost identical to the LB7, still missing parts for the emission control. GM fixed the injector problems when the LLY engine was released. Instead of injector issues, the LLY had overheating issues when driving in high temperatures or carrying heavy loads. The engine's original air intake system caused this.

The original turbo nozzle was very narrow, helping the engine to warm up more. A great solution is to use Duramax replacement parts such as an aftermarket cold air intake and turbo intake. Other problems with LLY were as follows:

  • Scratches on injector wiring harness
  • water pump failure
  • Glow plug failure
  • fuel pressure relief valve
  • Missing factory lift pump
  • EGR valve problems
  • Head gasket failure

Duramax LBZ: model years 2006-2007

The LBZ is widely recognized as the best Duramax engine ever built. You received this designation for the following reasons:

  • First Duramax with 6-speed Allison transmission
  • Missing emission control parts
  • GM solved the problems of the previous engines

The LBZ didn't have a major issue for the most part, the main issue being the need for a factory lift pump. Thankfully, it's a Duramax diesel part that you can install without breaking the bank. Experienced tuners found the only minor problem to be pistons breaking when trying to shift power above 600hp.

Duramax LMM: Model Years 2007.5-2010

The debut of the Duramax LMM engine coincided with new requirements for emission control parts. Mechanically, the Duramax LMM was almost the same as the LBZ, but with emission control parts not present on the LBZ. That was one problem, but another problem was the pistons.

As mentioned, excessive modifications to get more than 600 horsepower in the LBZ can cause the piston to crack. However, LMM pistons would break even faster if you tried to modify them beyond 600hp. This was due to the injector configuration.

The LBZ had seven fuel spray holes whereas only six were available on the LMM. This means that two jets of fuel came out in opposite directions from the screw. This causes hot spots to develop on the weakest part of the piston, which can lead to a crack.

The best years of Duramax

The Duramax can be an excellent engine for your truck if you avoid the model years listed above and stick with the durable and reliable ones. Here is a list of those trusted templates for you to choose from.

  • 2010 – 2017 Duramax LGH
  • 2011 – 2016 Duramax LML
  • 2011 - 2021 Duramax XLD25
  • 2012 - 2021 Duramax XLD28
  • 2014 - 2021 Duramax LWN
  • 2017-2021 Duramax L5P
  • 2019 - 2021 Duramax LM2

The LML was rebuilt for its 2011 model year debut. Power for this model year increased to nearly 400 hp and 765 pound-feet of torque. GM had to increase fuel system pressure to get that kind of performance without sacrificing emissions. Unfortunately, this affected the injection pump.

The only drawback of sudden fuel pump failure on this engine is that a large amount of chips spreads through the fuel system and contaminates the entire system. To fix this you will need a new fuel system which includes a new pair of fuel rails, high and low pressure fuel lines, injectors, a new fuel pump and filter. You also need to take down the tank to completely clear the metal debris.

You can avoid this problem by installing a lift pump that better filters dirt and air. Many pilots who own the LML often install the older Bosch CP3 which was first used on the LB7 engine. Despite having slightly lower pressure, it can still carry more horsepower.

The L5P is widely considered the best Duramax engine for emissions, and GM has fixed all the issues that plagued the emissions system and fuel injection pumps on previous models. Mechanically, the engine is reliable and owners have reported some issues.

The general problem with the L5P is that its MAP sensor becomes clogged with soot, which triggers a Check Engine Light. This is a simple problem; Install a MAP sensor spacer and use a powerful cleaner to remove any dirt.

Duramax LGH, Duramax XLD25, Duramax XLD28, Duramax LWN and Duramax LM2 go one step further to achieve better emissions thanks to the integrated diesel/urea injection feature. In addition, owners can increase the fuel consumption of their trucks with the help of exhaust gas aftertreatment.

The only problem that owners complain about is weak tie rods, which can be damaged during off-road driving, sled towing or drag racing. The exhaust aftertreatment/diesel particulate filter system is also a weak point that can cause problems.

Is it worth buying Duramax?

Duramax engines can be a great choice for your truck if you only opt for safe and reliable models. While these models aren't perfect, they feature less troubleshooting, allowing you to enjoy your engine for over 300,000 miles, although consumers have reported that their Duramax engines last up to 500,000 miles.

What year is the most reliable Duramax?

The most reliable and safe Duramax years you can buy are the models manufactured between 2011 and 2021. These models include Duramax LML, Duramax LGH, Duramax XLD25, Duramax XLD28, Duramax L5P, Duramax LWN and Duramax LM2.

What year does the Duramax have head gasket problems?

Duramax had head gasket issues on their 2001-2002 LB7 and 2004.5-2006 LLY models.

  • Author
  • recent posts

Hillary Princewill

Hillary is a gadget junkie who grew up spending a lot of time in her father's garage. His passion for cars includes everything from Formula 1 to the latest electric vehicles.

Recent posts by Hillary Princewill(see it all)

  • duramax years to avoid- February 1, 2023
  • Ram EcoDiesel years to avoid- February 1, 2023
  • Who manufactures Everstart batteries?- February 1, 2023
Top Articles
Latest Posts
Article information

Author: Gov. Deandrea McKenzie

Last Updated: 11/16/2022

Views: 5967

Rating: 4.6 / 5 (66 voted)

Reviews: 81% of readers found this page helpful

Author information

Name: Gov. Deandrea McKenzie

Birthday: 2001-01-17

Address: Suite 769 2454 Marsha Coves, Debbieton, MS 95002

Phone: +813077629322

Job: Real-Estate Executive

Hobby: Archery, Metal detecting, Kitesurfing, Genealogy, Kitesurfing, Calligraphy, Roller skating

Introduction: My name is Gov. Deandrea McKenzie, I am a spotless, clean, glamorous, sparkling, adventurous, nice, brainy person who loves writing and wants to share my knowledge and understanding with you.