6 Common Maxxforce 7 Engine Problems (Is It Reliable?)

From 2003 to 2012, the MaxxForce 7 was one of Navistar’s leading engine offerings to the truck market. For years, this powerful turbodiesel V8 was Ford’s go-to engine choice for its commercial vehicles. However, there are some significant issues with the MaxxForce 7 that you should know about.

In this article, we will take you on a tour of all the common problems with the Navistar MaxxForce 7 engine. Additionally, we’ll tell you about some precautionary maintenance tips too!

Most gearheads consider the MaxxForce 7 to be the engine that paved the path for Navistar’s downfall. After looking at the common engine issues including leaking radiators, cracked pistons, faulty exhaust systems, oil dilution, and Diesel Particulate Filter issues, it is hard to disagree with these critics.

MaxxForce 7 Engine Overview

MaxxForce 7 Engine

Before diving deep into MaxxForce 7 engine issues, we thought of giving you a brief overview of it. As mentioned earlier, the MaxxForce 7 was produced by a company named International Truck and Engine, a subsidiary of Navistar International.

The MaxxForce 7 had 6.4 liters of engine capacity, with its 8 cylinders placed in a V configuration. Navistar outfitted it with a high-pressure common rail fuel injection system, as well as a series sequential turbocharger.

The initial performance figures of the MaxxForce 7 were impressive. Initially, it produced 350 horsepower along with 650 lb-ft of torque.

But, not all versions of the MaxxForce 7 were made equal. The EPA2007 version of this V8 dropped the compound turbo configuration. In its place was a larger, single-stage turbocharger. This change alone dropped the power figures down to between 200 – 230 horsepower.

In 2010, the MaxxForce 7 underwent a significant overhaul. The cylinder block was updated with Compacted Graphite Iron (CGI) which reduced weight while being stronger than before. Additionally, the engine also got upgraded dual-compound turbochargers.

These changes brought along an increase in the overall torque figures. The V8 now produced up to 660 lb-ft of torque at 1600 – 2200 RPM.

The MaxxForce 7 took on another guise under the hood of 2008 – 2010 Ford Super Duty trucks. Here it was renamed the 6.4-liter PowerStroke. Differences in the name aside, both the MaxxForce 7 and the 6.4-L PowerStroke were victims of the same engine issues.

Most Common MaxxForce 7 Problems

The issues with the MaxxForce 7 are not limited to one area of the engine. In fact, these problems are spread throughout almost all of its critical parts. Don’t believe us? Take a look for yourself!

Here is a list of the most common MaxxForce 7 problems.

  • Radiator Leaks
  • Cracking Pistons
  • Bad Fuel Economy
  • Clogged EGR Cooler
  • Oil DIlution
  • DPF Issues

That doesn’t look good, am I right? Well, wait until you learn more about each of these issues. They get a whole lot worse!

1. Radiator Leaks

Let us start off by taking a look at one of the most widespread MaxxForce 7 engine issues – leaky radiators. The poor design of the radiator is the main cause of this issue.

You see, the bonding on the engine’s plastic radiator tanks left much to be desired. Over time, these could crack and lead to the formation of coolant puddles under your truck. The constant engine vibrations did not help the cause either.

The frequent leakage of coolant leads to overheating. If the issue goes unfixed for a while, the constant overheating could result in permanent engine damage.

Replacing the radiator is the only way to permanently fix this issue. Furthermore, consider getting a radiator support bar to further increase its durability. The support bar stops the radiator from flexing and twisting, prolonging the lifespan of your cooling system in the process.

2. Cracked Pistons

The pistons which came with the MaxxForce 7 V8 were noticeably weaker than its competitors. The cracks typically start at the thin edge of the piston’s fuel bowl. These slowly develop and get worse over time. Sometimes, the cracks may spread across the entire length of the piston.

Cracked pistons are bad on their own, but they can lead to severe issues like melted injector tips down the line as well. Older MaxxForce 7 engines with higher mileage counts are the most vulnerable to piston cracking.

Replacing the pistons on the MaxxForce 7 is an expensive and time-consuming task. In addition to the parts, the labor costs will be sky-high as well. This is mainly because the entire engine has to be torn down in order to gain access to the pistons.

However, the pistons on the MaxxForce 7 were considerably more durable than the ones on the 6.4-liter PowerStroke. Most Ford Super Duty owners replaced their OEM pistons with ones from the PowerStroke for additional durability.

3. Bad Fuel Economy

Being a heavy-duty truck engine, it is safe to say that most won’t put the MaxxForce 7 and fuel economy in the same sentence. But, this turbodiesel was especially gas hungry, even when compared to its peers.

Navistar equipped the Maxxforce 7 with a Diesel Particulate filter (DPF). This was the main cause of poor fuel economy.

The active regeneration technology in the engine used diesel to clean the DPF. This took a hit on the engine’s overall fuel economy. In addition, constant active regeneration in city driving reduced the fuel economy even further.

4. Clogged EGR Cooler

The EGR cooler of the MaxxForce 7 V8 was responsible for increasing the density of the exhaust gas. The cooler did this by decreasing the temperature of the exhaust gases. Increasing the EGR system’s performance was the main goal of this operation.

The EGR cooler of this Navistar engine faced constant issues. The coolant used for cooling the exhaust gases broke down over time, clogging the cooler in the process. To make matters worse, issues with the EGR cooler can take a toll on the turbo as well.

Issues with the EGR system cause soot to re-enter the engine. Sometimes, this soot finds its way through the turbine housing and sticks to the vanes. If this happens, there is a high likelihood of turbo actuator failure.

5. Oil Dilution

Oil dilution is another major problem that has plagued MaxxForce 7 owners for many years. This is an issue that also shares with its PowerStroke counterpart.

As aforementioned, these engines come with a technology called active regeneration. Here, diesel is injected during the exhaust stroke with the aim of elevating EGTs. Active regeneration also burns off hydrocarbons adhering to the DPF.

However, this process has the unnecessary repercussion of mixing diesel fuel with engine oil. Diesel isn’t a good lubricant, so the mixing of the two liquids increases the wear and tear on your engine’s internals over time.

6. DPF Issues

On top of being the main reason behind bad fuel economy, the Diesel Particulate Filter of the MaxxForce 7 is the cause of some other issues too.

Early versions were prone to leaking, and the DPF sensors are well known for premature failures. However, the most notorious issue with the MaxxForce 7 is clogging.

A clogged DPF sensor restricts the exhaust system. As a result, you will experience a noticeable downturn in engine performance. This issue needs to be sorted out immediately to prevent further damage to the engine.

Preventive Maintenance Tips To Keep The MaxxForce 7 Running Smoothly

Although the MaxxForce 7 has one of the worst reliability records we have ever seen, there are some precautionary measures you can take to give it a better chance of survival.

Invest In A Coolant Filtration System

A coolant filtration system is one of the best fixes for the MaxxForce 7’s constant EGR issues. These systems limit coolant breakdown, also increasing the liquid’s lifespan in the process.

Keep An Eye On Engine Oil Levels

Paying frequent attention to your engine oil will go a long way in limiting oil dilution. We recommend you take dipstick readings at least once a week. If the oil level is too high, perform an oil change and filter replacement immediately.

Navistar recommends you change the engine oil of the MaxxForce 7 once every 10,000 miles. Instead, perform the oil changes every 5000 miles for maximum engine safety.

Also, make sure to only use engine oil that meets the specifications set by the OEM. Using cheap-quality oil might seem like a great way to save a buck. But, you’ll regret it once the engine issues start popping up.

Fit Aftermarket Cooling Accessories

Fitting a cold air intake and an aftermarket intercooler are two modifications that can improve the fuel economy of your turbodiesel engine. You can also get a tune that helps the engine to breathe more freely.

Other methods of increasing fuel economy – such as turning off the emissions devices do exist. But, we advise you against doing so, as doing so is outlawed by the government.

It is safe to say that the Navistar MaxxForce 7 was one of the most powerful turbodiesel engines back in its heyday. But, considering the constant maintenance issues that have since surfaced, you are better off spending money on a competing powerplant.

Related articles:

4 Common Problems With Volvo D13 Engine

6 Most Common GM 2.7 Turbo Engine Problems

5 Common Chevy 6.0 Engine Problems (Is It Reliable?)

Who Worked on This?



I'm the guy responsible for ensuring that every blog post we publish is helpful for our reader.

Mahir Ahmed


I'm the guy responsible for ensuring honest, informative, accurate and helpful guide to the reader.

Leave a Comment