Worst Years For The Duramax (Revealed)

ByKern Campbell

Most people who drive a diesel-fueled engine vehicle are familiar with the Duramax engine that has been on the market since 2001. A partnership between General Motors and Isuzu, the Duramax was meant to replace the Detroit Diesel as a better engine. 

Unfortunately, the Duramax engine didn’t always perform as users desired. The worst years for the Duramax engine include the 2001-2004 Duramax LB7, 2004-2005 Duramax LLY, 2006-2007 Duramax LBZ, 2007-2012 Duramax LLM, and 2007-2016 Duramax LML.

Are you wondering which Duramax engines you should avoid? If so, let’s look at some of the worst years for the Duramax and which ones you can safely purchase.

What are the Worst Model Years for the Duramax?

Diesell Engine Pistol Being Replaced

Although Duramax has been on the market since 2001, they have suffered from various problems in many models. In addition, many of the models have been prone to a wide range of downsides, including issues with the fuel pump, water pump, and injectors.

If you are considering purchasing a Duramax engine or a vehicle with one already installed, there are specific models you should consider avoiding. Doing so can save you time, money, and headaches.

2001-2004 Duramax LB7

Like many original models, the LB7 was the first Duramax engine on the market. However, since it was set to replace the Detroit Diesel, it had to be one with high-quality parts and reliability that would last for years to come.

This model was well known for its cast-iron cylinder block and was a 6.6-liter V8 engine that was like no other. It was famous for the quieter sound and excellent fuel economy that it gave to vehicles equipped with the Duramax.

As with many original models, there are always features that can be improved, and the Duramax LB7 has many. Unfortunately, although they were a great replacement engine for the previous model, they did not come without problems.

Some of the most common problems with the LB7 model were:

While many of the issues mentioned above are fixable, they could be costly for the vehicle owner. The last thing you want to do when you have a new vehicle is to spend time and money on repairs so often.

2004-2005 Duramax LLY

The Duramax LLY model was created to answer many of the issues that popped up from the previous model. Unfortunately, in most cases, people viewed it as the same model but with a few upgrades that were supposed to improve it.

One of the upgrades to this model was to equip it with better fuel economy and emissions control which would appeal to many people. This was due to the EGR valve added to this model.

Although this model came with a variety of upgrades also, including the addition of the variable vane turbocharger, it did not come without problems. Many experts say this model was not the answer to the many issues in the LB7 model.

Here are some of the problems the LLY is known to have:

  • EGR valve problems
  • Overheating
  • Failure to the water pump
  • Failure of the head gasket
  • Issues with the injector
  • Malfunction with the glow plug

Again, many people who upgraded to this model, expecting it to be the answer to their previous problems, were somewhat disappointed. With the many issues found in the last model still present in this one, there was still the issue of them breaking down often.

2006-2007 Duramax LBZ

In true Duramax tradition, the LBZ model was created to address many of the problems that the LLY and LB7 models had. In addition, it was upgraded with newer technologies and parts that make it one of the most desirable models on the market.

Duramax created the LBZ with a noticeably thicker engine block than the previous models. As a result, this model gave way to better horsepower and reliability, improved connecting rods, and changes to the fuel injection system.

However, like the previous models, the LBZ has not been without its problems over the years. But with a short run due to emissions regulation changes, the model became obsolete in its availability.

Check out some of the more common issues the LBZ experienced:

  • Failure of the water pump
  • Malfunction with the glow plug
  • Cracked piston
  • EGR valve problems
  • Failure of the injector

Even though this list is not exhaustive of the issues this model had, it should give you a good idea that it suffered from some of the same problems previous models had. Because of this and the short production run, the LBZ is considered one of the worst years for the Duramax engine.

2007-2012 Duramax LMM

Created in 2007, the LMM model was developed to replace the LBZ model to make needed upgrades and improvements. One of the focuses of the development was to strengthen the emissions controls even more than the previous models.

With the added components meant to help with emissions, such as the diesel particulate filter, the LMM was supposed to be more reliable and durable. Instead, the opposite became true; however, with these added features, the vehicles that held these engines became less fuel efficient and suffered some of the same issues.

What made the Duramax LMM model more attractive to many people was the price tag that did not break the bank. Because of its affordability, more people were able to afford the engine despite it not being as reliable.

Here are some of the issues that the Duramax LMM model had:

  • Problems with the fuel system
  • Leaks in the transmission lines
  • Blocked diesel particulate filter 
  • Cracked pistons

Since the LMM model was not as reliable as the previous models or other brands of engines, those who own them may spend more money on repairs than they may anticipate.

2007-2016 Duramax LML

Close up of diesel fuel injector in engine block Worst Years For The Duramax (Revealed)

The Duramax LML engine model was introduced after more regulations concerning emissions came into effect. This model answered the many regulations with the development of more emissions controls.

The LML model is said to be a more powerful engine with the creation of more powerful pistons. Additionally, the improvement to the injector and fuel system allowed the engine to be fueled with a small amount of biodiesel.

This model, of course, has not been without its problems despite the additions that made the engine more durable. Even though the engine is said to have better fuel efficiency than previous models, it may be a trade-off for the issues that it has had.

Check out some of the problems the Duramax LML model may have:

  • Fuel pump failure
  • Problems with the EGR valve
  • Injector pump problems
  • Failure of the oxygen pump

Although this engine was created to make the heavy-duty truck more durable over the long haul, the issues it often suffered from got in the way. 

What Year Did the Duramax Have Injector Problems?

Although several Duramax models have had some issues with the injector, the year known for having the most is the flagship model, the 2001-2004 Duramax LB7. With this being the first one they made, models were developed after this year to fix the fuel injection system issue.

It is widely known that if you were to purchase this model or have owned one in the past, you most likely would have had trouble with the injection system.

However, GM did realize the injection system had issues and released a notice to owners to have it replaced. 

What is the Best Duramax Model Year to Own?

Since there are no perfect models of engines on the market, even the best ones can have specific issues. This is the case with the 2017-Present Duramax L5P engine since it also has certain problems. 

This model is considered to be not only one of the best Duramax models but also one of the safest and most reliable. This is partly due to the more durable engine block and other safety features and technology.

Which Duramax Model Years are Safe to Buy Used?

Duramax engine on garage floor

Not all Duramax models were a complete failure since quite a few can stand the test of time. In addition, these models were developed with more reliability and fuel efficiency than others on the market.

2010-2017 Duramax LGH

This model, created to be used in full-sized vans, is deemed to be one of the safest engines to purchase. This is due to the added features introduced after tightening the emissions regulations.

2017-Present Duramax L5P

Also featured as one of the safest Duramax models on the market comes the L5P with its better fuel economy and technology features. This model also added features such as a more robust engine and various emissions controls.

2011-2021 Duramax XLD25

Although this engine is considered one of the smaller of the other models, it is also deemed one of the safest. Created to be put in SUVs, mid-sized trucks, and more, this model is the epitome of reliability and durability.

2012-2021 Duramax XLD28

Similar to the previous model, this engine was also developed to be one of the smaller models on the market. However, its fuel economy and safety features do not keep it from being one of the safest you can purchase.

2014-2021 Duramax LWN

The LWN model is deemed to be one of the safest on the market and one of the cleanest. The cooled EGR system was developed to answer the strict emissions regulations.

2019-2021 Duramax LM2

This model of Duramax engines is said to be one of the smallest of the line, even smaller than the previously mentioned models. Designed to be put into a variety of vehicles, including half-ton trucks, the model boasts excellent fuel economy and reliability, making it one of the safest on the market.

Final Thoughts on the Worst Years for the Duramax

The bottom line regarding the Duramax engine’s worst years is that while several of these models have issues, the Duramax brand is still one of the best on the market.

In addition, the problems with the various models have taught the company many things over the years, helping create newer models overall.