What Is The Most Difficult Diesel Engine To Work On? Here's What Mechanics Have To Say

• Cars
• Trucks

There have been many reliable diesel engines over the years. Some are easy to work on, while others are a bit more challenging. The Ford 6.4-liter Power Stroke falls into the latter category, while also not being particularly dependable. Because its engine bay is so densely packed, the 6.4-liter has earned quite a reputation among mechanics for being one of the most difficult diesel engines to work on.

Since it was introduced in 2007, the 6.4-liter was continuously updated. Ford eventually gave it new emissions technology, better turbochargers, DPFs, and EGR coolers. This made it quite difficult to access many of its essential components, like the head gasket, for example. If you wanted to fix a blown head gasket on a 6.4-liter, it requires either pulling the entire cab off or taking out the engine – a task that can take up to 48 labor hours to do.

One mechanic on Reddit noted that "lots of common issues require a cab lift", including the turbocharger, cracked pipes, oil coolers,and the high-pressure fuel pump. Moreover, the 6.4 also suffers from internal failures, and with such a tightly packed engine bay, even routine repairs can be difficult and costly. Ultimately, the 6.4-liter is a very picky engine with a severe maintenance schedule.

Ford 6.4-liter Power Stroke common issues and maintenance challenges

Many of the 6.4 Power Stroke's emissions components are known to fail prematurely. These include the diesel particulate filter, the exhaust gas recirculation system, and the oxidation catalyst. Some common 6.4-liter Power Stroke problems, like the ones related to the DPF, can be both difficult and expensive. Although it is possible to delete these systems to reduce maintenance, it is illegal and can cost between $500 and $3,000.

The turbochargers are also tightly packed and expensive to maintain, especially because they are prone to bearing wear and sticking vanes. Moreover, fuel dilution is also common, and many owners report needing to change the oil every 3,000 to 5,000 miles to stay on the safe side. Removing the up-pipes on a 6.4 Power Stroke can be very unforgiving because they are positioned behind the firewall, and they also require a cab lift.

On top of all of this, numerous examples suffered from radiator leaks, which can also take hours to remove and replace, while costing as much as $2,200. A teardown specialist from I Do Cars noted on the 6.4 that "the fans of this engine are those that get paid to service them." Given the inaccessibility of many essential components, the high labor hours required, the engine's inherent unreliability, and the fact that the emissions systems were clearly an afterthought, the 6.4 is definitely a handful.

How to bulletproof a 6.4 Power Stroke

The 6.4 Power Stroke was only offered between 2007 and 2010, partlybecause it was so problematic. Even so, there are ways how you can bulletproof a 6.4 to make sure it lasts as long as possible. For starters, since removing the emissions systems is illegal, you can upgrade them with aftermarket solutions by installing a heavy-duty cooler. Another relatively cheap add-on — $150 to $200 — is an aftermarket coolant filtration kit.

Investing in stainless steel up-pipes, an aluminum radiator, and better head studs is also going to help tremendously. As previously mentioned, the high-pressure fuel pump on a 6.4-liter is difficult to reach and can cost between $3,500 and $14,000 to replace. Adding a lift pump with filtration or a fuel filter kit can help make it last longer, while turbo reconditioning kits and head gasket kits are also a good upgrade for heavy-duty use.

Although it is difficult to maintain a Power Stroke 6.4-liter, it is necessary. Since there is only so much you can do to bulletproof it, some people are even willing to go the extra mile and swap them out for a more reliable engine altogether. For example, putting a Cummins engine in a Ford truck will cost you a lot of money. However, there are kits and custom solutions available if you are up to the task.

Our methodology

Choosing a single engine as the most complained about is never going to be a zero-sum game. Individual experiences will always vary, and not all examples will be as bad. We partly chose the 6.4-liter Power Stroke because it is a problematic mass-produced engine built by a major manufacturer for some of the most popular trucks in North America.

However, the main reason is the fact that the 6.4-liter Power Stroke is widely complained about by mechanics on discussion boards and sites such as Reddit, Practical Machinist, Bob Is the Oil Guy, JustAnswer, the PowerStroke Forum, Ford Trucks Forum, Diesel Mag, MotorTrend, FASS Motorsports, ProSource Diesel, the Diesel Technician Society, and Diesel Resource.