6.6 Duramax Diesel Issues (6 Major Issues Resolved) (2023)

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The 6.6 Duramax is one of Duramax's most reliable engines, lasting for hundreds of thousands of miles.

However, if you put that aside for a second and consider some of the issues that the engine model is stuck with, at first glance it might seem like they completely damage the engine.

However, many of these issues can be fixed with simple aftermarket upgrades.

“Before we look at how to fix these issues, it's important that we detail the problems with the 6.6 Duramax Diesel, which range from fuel injection issues, fuel injection wiring harness chafing, overheating and blown seals to glow plug failures. and EGR problems. enough. Once you can figure out why your 6.6 Duramax engine is crashing, that would be the first step forward."

Are you ready to take a break from every model car you've ever used and try car engines like 6.6 Duramax? Well, we wouldn't say you made a bad choice.

Nonetheless, we think these are things you should know about the engine before committing to one.

table of Contents

Is a 6.6 Duramax Diesel a good engine?

The 6.6 Duramax is available in several variants with different components precision-engineered to meet global emissions reduction requirements, as well as to maintain and, where possible, increase torque and horsepower over time.

The 6.6 Duramax is a great option for those looking to maximize traction and performance.

If you use a full-size pickup, you can be sure that this V8 engine will give you everything you need in terms of power and torque.

The 6.6 Duramax is capable of producing incredible amounts of power with very low emissions compared to other engines of a similar brand and is equipped with increased efficiency equipment.

The temperature control of this region keeps the cylinders at low pressure, while allowing the user's truck to get unbelievably beastly power.

6.6 Problems with Duramax Diesel

01. Head gasket failure

Although head gasket failure is more common on LLY Duramax than any other generation of 6.6 Duramax, it is still a fairly common problem on all 6.6 Duramaxes.

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This seal head failure can be attributed to the turbocharger and overheating issues caused by inefficient cooling systems. Other factors can also lead to this.

An aftermarket modification could also be to blame, especially if the mileage is very low. Therefore, these factors can cause the head gasket to malfunction.

02. The turbocharger

Due to its flow characteristics and size, the Garrett turbocharger often causes head gasket problems.

If there is more power and boost pressure, the engine head gasket may fail due to increased wear.

This is especially the case if your truck still has the intake manifold or turbo nozzle. These limitations cause excessive heat and force the turbocharger to work beyond its capacity.

03. Overheating

Overheating is another major cause of head gasket failure. This can be attributed to the poor cooling system of the engine.

With a high flow turbocharger combined with small radiators, your engine is sure to take on a storm.

This mostly happens when you are towing heavy loads or in very hot weather.

Under these conditions, the temperature of the fluid increases, which causes wear of the seals. Here are common signs of burned stamps to look out for:

  • Sudden loss of coolant
  • Leaks in the engine compartment or on the floor
  • White smoke
  • oil contamination

So what is the solution?

If you experience a head gasket failure, we recommend that you take your truck to a shop to have it properly repaired. This job generates you an unbearable amount.

Most shops will charge you 25-40 hours of labor for the tedious task involved in replacing the head gasket.

For this reason it is highly recommended that you do not attempt to replace it yourself unless you are a mechanic.

04. Chafing on the injector harness

As your 6.6 Duramax engine ages, you will begin to notice chafing on the injector wiring harness. Injector wiring harness rubbing is caused by a number of factors that combine or are influenced independently.

It's usually vibration, heat, and mostly just normal wear and tear that any engine can go through. This causes the injector harness to ride against other engine components.

Eventually this happens until the wiring is exposed. Common signs to look out for are:

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  • no boot/idle
  • rough race
  • power reduction
  • error codes

The solution to injector harness chafing is simply to schedule a replacement appointment.

Upgrading the wiring harness from your old injector will simply eliminate the problem and even prevent exposing parts that can cause very serious problems.

05. Water pump failure

Water pump failure seems to be a common weak point on many Duramax engines. Over time, he would discover that the engine's factory water pump seals began to fail.

This normally starts around 80,000 miles. How do you know that your water pump is faulty?

  • Noticeable coolant leaks
  • loss of refrigerant
  • excessive heating

The solution to water pump problems is to replace the bad one with an aftermarket product or a factory product.

The good thing about aftermarket water pumps is that they can last much longer since they are designed to correct the design flaws of the old original pump.

Sometimes factory parts seem to be more reliable than aftermarket parts as they may perform better than cheap aftermarket alternatives.

06. EGR problem

Like many early emission devices, EGR systems are a common problem on Duramax engines.

The EGR system reduces emissions even by redirecting exhaust gases to the engine's combustion chamber.

EGR systems use coolant to reduce exhaust gas temperatures.

While this system is effective in reducing NOx emissions, the coolant can be subject to degradation, which is typically a result of the extreme heat generated by the exhaust.

Carbon can also build up on the EGR valve or EGR cooler. This can cause the EGR system to fail completely.

How can I fix EGR problems?

Well, if you have an EGR system that seems to be working, it might be time for a service.

EGR systems are a simple and inexpensive solution, but remember that they are not legal modifications to road legal vehicles.

However, they are allowed to be in race trucks. So if you have a vehicle that doesn't drive on the street, this is a great option.

If you regularly use your truck for travel and work, you'll need to replace your EGR with aftermarket alternatives. Or you can replace the kits with OEM products.


Lack of factory lift pump

This is a communication issue with most Duramax engines that many Duramax 6.6 engine users have complained about as frustrating.

Fuel lift pumps are essentially low pressure pumps that draw fuel from the tank and provide constant fuel pressure to the injection pump.

Since the 6.6 Duramax does not have fuel pumps, the CP3 injection pumps are now in charge of removing the fuel from the tank and also pressurizing it to reach the injectors.

The result of that? Increased wear on the CP3 injection pump.

Fortunately for many users, the CP3 seems to be very durable and capable, making breakdowns a less common problem where low mileage trucks are concerned.

Not having a lift pump becomes a mistake when you need to upgrade your 6.6 Duramax.

When you decide to do advanced tuning or other performance modifications, you need constant fuel. Otherwise, you won't get the most out of the update.

You may lose fuel rail pressure during acceleration. So what good are your modifications?

Fuel transfer pumps solve this problem by providing a constant flow of fuel, and interestingly enough, they can be adjusted to balance fuel demand.

How do I fix the missing fuel lift pump on my 6.6 Duramax?

Well the simple answer to that isJust add a lift pump. The fact that the engine is not equipped with its own fuel pump does not mean that it does not support the installation of one.

The good thing is thatfuel feed pumpsThey are not expensive and even with a stuck truck they can make a world of difference.

Whether you're using a stock truck or a modified one, purchase a fuel lift pump kit for a fuel filter/lift pump system.

The result of this is that your engine now burns cleaner fuel and of course there are now fewer emissions, longer fuel system life and better fuel economy.

How many kilometers does a Duramax 6.6 last?

You can get up to 350,000 miles on a well-maintained 6.6 Duramax pickup.

According to Prosource Diesel, miles over 350,000 miles are known as high mileage diesel trucks used with a Duramax engine in service.

Anything over 350,000 miles can also safely be called high mileage if it's a Powerstroke diesel engine.

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So when it comes to going long distances, 6.6 Duramax can be trusted to give the user good stats, especially since most users use the engine for hours towing.

How reliable is the 6.6 Duramax Diesel?

The 6.6 Duramax has been in production batches since 2001. It has proven to be relatively reliable on a large scale and can cover most of the options and needs that most users expect from a powerful truck engine.

That's not to say the engine doesn't have its own issues, some of which are inherent in the engine's design style and components. In conclusion on this matter we can say that the 6.6 Duramax is a good engine that can be counted on to satisfy the basic needs of a daily user.

What is the best and worst year for the 6.6 Duramax?

The worst years (2001-2009)

6.6 Duramax has a long production history. We recommend that you avoid any vehicle equipped with a 2001-2009 Duramax engine.

For the 6.6 Duramax, newer models are built with improved performance in mind. The first engine was the Duramax LB7, found in the 2001-2004 Chevrolet Kodiak and Chevrolet Silverado.

In the lineup it looked the simplest due to the lack of a diesel particulate filter or EGR.

Later models still had some really terrible issues that the user faced early on.

We recommend going with a 6.6 Duramax engine and avoiding the years highlighted in this section.

Best years (2010-2019)

The Duramax engine underwent major changes and modifications in a revolutionary way in 2011. However, most changes must comply with new emissions regulations.

Although the newer models are a bit more complicated than the older ones, they still seem to be more reliable.

The safest Duramax models are the 2011-2021 models. These go one step further to offer better emissions. This can be attributed to the exhaust gas injection feature on these newer models.

6.6 Duramax Engine Specifications

Engine Variationyears of productionPDtorqueoil capacityEngine oil/filter every 6 monthsEngine coolant/ 10 years
6.6 LB72001-2004300 CV a 3100 rpm520 lb-ft bei 1800 U / min10 liters10.00p miles150,000 miles
6.6 LLY2004 a 2005310 CV a 3000 rpm590 lb-ft bei 1600 U/min10 liters10,000 miles150,000 miles
£6.62006 a 2007310 CV a 3000 rpmLow: @ 1600 rpm, 590 pound-feet

Alto: @ 1600 rpm, 605 lb-ft

10 liters10,000 miles150,000 miles
6.6 LMM2007-2011330 CV a 3000 rpm620 lb-ft bei 1600 U / min10 liters10,000 miles150,000 miles
6.6 LML2011 – 2016397 CV a 3000 rpm765 lb-ft bei 1600 U / min10 liters10,000 miles150,000 miles
6.6 L5P2017-present445 CV a 2800 rpm910 lb-ft bei 1600 U / min10 liters10,000 miles150,000 miles.

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Frequently Asked Questions (FAQs)

What is the best Duramax engine to buy?

Many users agree that the L5P, released in 2017, is one of the best Duramax engines you can own.

It's more durable than many other 6.6 Duramax models and has a staggering 445 hp and 910 lb-ft of torque. The L5P was a replacement for the LML on Silverado trucks.

What tuner can I use for my 6.6 Duramax engine?

  • Bully Hund 40420
  • Edge Products 85400 Diesel Tuner
  • DiabloSport 8245 Diesel Tuner
  • Hypertech 32501 Diesel Tuner

What are the best ways to get better gas mileage from a Duramax 6.6?

  • If possible, don't let your truck idle for long periods of time. Idling depletes fuel and affects gas mileage
  • Check your tire pressure
  • Relax your gas consumption
  • Maintain your Duramax truck regularly

last words

6.6 Duramax is one of the best generations of GM-Isuzu fusion. These diesels are incredibly good when it comes to performance expectations like towing or dumping.

However, there are a few problems with them, most directly related to the way they were designed.

This covers these issues in detail and also provides solutions for each problem.

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If you decide to look away from the 6.6 Duramax's shortcomings for a second, you immediately realize that these are excellent engines and their problems don't weigh heavily on them.


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