The 6.4L Powerstroke was an upgrade from the problematic 6.0L diesel engine, especially in terms of reliability.
However, the International-built engine still suffered from gremlins carried over from the 6.0L. Regardless, the 6.4L remained a popular engine due to its horsepower upgrades.
You can make a 6.4L Powerstroke more reliable by replacing the radiator, the pistons, or the EGR coolers with durable aftermarket options. Also, you can replace the engine oil at regular intervals and install a coolant filtration system.
This piece will explain how to make a 6.4L reliable. Some tips will involve replacing parts, while others require you to install additional ones.
1. Replace the Stock Radiator
The radiator will likely be the first part to fail on your 6.4L Powerstroke. Cracks form on the ends of the plastic radiator tanks due to their poor quality and the massive engine vibrations. As a result, coolant leaks out of the gaps.
If you see a pool of leaked coolant under your vehicle, the most likely culprit is the stock radiator. Other signs of leaking coolant include overheating and steam from the engine.
The only solution is to replace the stock radiator with an aluminum aftermarket radiator. You can install a radiator support bar to add rigidity and prevent flexing of the unit due to engine vibrations.
For tractors, I recommend the CoolingCare Aftermarket All Aluminum Tractor Radiator for Ford/New Holland (available on Amazon.com).
Not only will it improve your cooling by 30 percent, but despite its aftermarket status, it’s been thoroughly inspected for any issues that may keep your radiator from running smoothly.
2. Replace the Pistons
The pistons of the 6.4L Powerstroke had a major flaw: The way they were constructed made them susceptible to cracking.
International made pistons with a sharp lip with little material at the top. As a result, the piston cracks, and the engine is unable to combust properly.
Unfortunately, you may only realize that your 6.4L Powerstroke has a cracked piston once the piston fails with a characteristic bang. The problem seems to affect all 6.4L Powerstroke engines but at different times.
One way to identify this problem is to loosen the oil cap on a running 6.4L. If there’s a crack on one of the pistons, the increased crankcase pressure will blow the cap off.
Note: If you want to check for this problem yourself, be careful since the lid flies off at high speed. It isn’t a surefire way of diagnosing the issue, as normal crankcase pressures can cause steam to rise from the oil cap on a running engine. Instead, you may want to tow your car to a professional repair shop.
Similar to a damaged stock radiator, the best fix for a faulty 6.4L piston is to replace it. Maxxforce pistons are the common replacement as they have a rounded lip with extra material that copes better with heat and is more resistant to cracking.
You’ll also want to coat these pistons to increase their heat tolerance and durability. You can grab one of these CERAKOTE Elite Series Oven Cure Ceramic Coating Starter Kits (available on Amazon.com) and perform a DIY preventative measure with the help of a digital application guide.
3. Replace the EGR Coolers
International improved the 6.4L’s Exhaust Gas Recirculation (EGR) system by adding an extra EGR Cooler since the troublesome 6.0L had one EGR cooler.
The EGR system reduces the combustion chamber temperature by introducing exhaust gasses. The decreased temperature inhibits the formation of nitrous oxide while maintaining engine performance. Hot exhaust gasses pass through EGR coolers so they can be cooled by the time they get into the combustion chamber.
Stock EGR coolers often crack, introducing water or coolant into places they don’t belong.
You can spot a leaking EGR cooler via steam from the exhaust. That means water has seeped into the exhaust system, where hot gasses have vaporized it. But if you spot white smoke from the exhaust rather than steam, refer to this article for causes and fixes.
If you want to replace your 6.4L Powerstroke’s cooler, I recommend the aftermarket varieties as they last longer and can improve your engine’s power output.
4. Install a Coolant Filtration System
The EGR coolant is often exposed to high temperatures, leading to its breakdown. The heat gradually deteriorates the coolant or the EGR cooler’s pipes, which introduces particles into the system.
These particles can clog the cooler, reducing its effectiveness and affecting emission control.
For that reason, you need to install a coolant filtration system like the 6.4L Revive Kit #4 w/ARP Studs Head Gaskets Oil Cooler (available on Amazon.com). The kit includes everything you need to keep those little gremlins out of your engine’s coolant system.
5. Install an Extra Oil Cooler
Sometimes, the problem is with the oil cooler rather than the engine itself. Similar to the EGR cooler, the oil cooler’s coolant can cause a blockage.
For that reason, you need to keep an eye on the temperatures of the engine’s oil and coolant. If the difference between the two goes over 14 degrees, the system isn’t cooling the oil fast enough.
Unfortunately, you can’t fix an oil cooler after it clogs. You’ll have to replace it — preferably with an aftermarket version.
For extra durability, install an additional oil cooler. It reduces the load on the stock engine oil cooler and increases the engine’s oil-cooling capacity.
The Mishimoto MMOC-F2D-08 Replacement Oil Cooler (available on Amazon.com) is a decent cooler for the 6.4L Powerstroke. It comes with a lifetime warranty, though you’ll have to ask a professional for help installing this one.
6. Replace the Engine Oil Regularly
You may have heard that a 6.4L Powerstroke’s oil needs to be replaced at twice the average rate.
That’s owing to the vehicle’s emission-reduction system, specifically the Diesel Particulate Filter (DPF). The DPF is designed to trap soot, a harmful byproduct of diesel combustion.
A significant drawback of the DPF is its finite capacity to hold soot. The soot must be burned into ash to prevent the DPF from clogging.
Unlike other engines (which spray diesel directly into the exhaust), the 6.4L Powerstroke sprays DPF-cleaning diesel in the combustion chamber during the exhaust stroke. The diesel gets pushed out alongside the exhaust gasses.
As you can imagine, leftover bits of fuel eventually along the cylinder wall. These bits get into the engine oil, interfering with its ability to keep the engine in good working order.
Therefore, you’ll want to replace the engine oil on a 6.4L Powerstroke every 4,000 to 5,000 miles (6,440 to 8,050 km).
By doing so, you’ll prevent the oil from getting too contaminated and introduce unblemished oil into the system, improving your engine’s durability.
7. Use HOAT Coolants
The 6.4L Powerstroke engine runs very hot, placing an extra burden on the coolant. Engine coolant absorbs heat from sweltering engine components before releasing the heat through the radiator.
Unfortunately, the coolant sometimes gets so hot that it erodes engine channels, causing a phenomenon known as “coolant cavitation.”
If the erosion goes unchecked, the coolant can create an opening that leaks coolant into the oil, causing a disastrous engine failure.
You can prevent coolant cavitation by adding special additives to the coolant reservoir. The metallic salts protect the engine components from corrosion.
Alternatively, you can use coolants with hybrid organic-acid technology (HOAT). HOAT coolants last longer than traditional coolants and are formulated to protect the engine.
For example, the Zerex G05 Phosphate Free Concentrate Antifreeze/Coolant 1 GA (available on Amazon.com) works for diesel and gas engines. As you can guess from its name, it can also help protect your coolant from freezing during colder temperatures.
8. Remove the DPF
Most of the 6.4L Powerstroke’s reliability problems stem from the measures introduced to reduce emissions, including the DPF. Removing it solves several reliability issues, but doing so might violate federal laws.
The Clean Air Act criminalizes the removal of the DPF or modification of the vehicle to allow exhaust gasses to bypass the filter. The fine imposed by the EPA varies depending on the vehicle’s weight, miles covered, and the intent to tamper with the DPF.
However, If you use your vehicle strictly for off-roading or competitions, you can delete the DPF. If you’re in doubt as to whether you can delete this part, you can always consult someone who’s more familiar with the related legalities than you.
It’s a shame an engine as good as the 6.4L Powerstroke has so many reliability problems. Thankfully, you can improve its durability by installing several aftermarket components and monitoring the vehicle closer than you would other cars.
The modifications will cost you, but they will likely cost less than the damage caused by poor reliability. Of course, if you’re in doubt about the root cause of the issue, consulting a professional is your best bet.
I listed the worst 6.4 Powerstroke years to avoid in this article.