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13 Most Common 6.4L Powerstroke Problems & Fixes

Most Common Issues 6.4L Powerstroke Owners Encounter

While the 6.4L Powerstroke offered some improvements over the 6.0, they are still largely unreliable. There are a number of common 6.4L Powerstroke Problems that owners of these trucks consistently encounter. What’s worse is that like the 6.0L Powerstroke, repairing the 6.4 often requires raising the cab to easily access the engine. This makes any repair more expensive.

Thankfully, because these 6.4L Powerstroke Problems are so common, we now know many of their causes, as well as how to fix them. Most 6.4L Powerstroke Problems are attributed to a poor factory design and new emissions devices. Here’s a list of the most common issues found on 2008-2010 Ford Superduty trucks with the 6.4L Powerstroke Diesel engine.

13 Common 6.4L Powerstroke Problems

  • Oil Dilution
  • Leaking Radiator
  • Poor Fuel Economy
  • Clogged Diesel Particulate Filter (DPF)
  • Clogged Engine Oil Cooler
  • EGR System Failure
  • Cracked Pistons
  • Cracked Up-Pipes
  • Cylinder Washing
  • High Pressure Fuel Pump Wire Chafing
  • Fuel System Failure and K16 Injection Pump Self-Destruction
  • Cracked Blocks
  • Front Cover Cavitation

Now that you know the most common problems found on these trucks, it’s time to dive deep into every specific problem and how to fix them. If you want to skip to a section, simply click on one of the bulleted links. If you’re not looking for a specific problem, simply scroll down. Let’s get in to it!

1. Oil Dilution

Oil dilution is an extremely common problem that 6.4L Powerstroke owners face. Have you ever changed your engine oil on your 6.4 by yourself? You might have been surprised that after draining the oil out of your truck, you found a ton of extra oil. Several quarts and sometimes even over a gallon of extra oil can be removed when changing your engine oil.

It’s not really oil though. What you’re experiencing is oil dilution. That extra liquid is diesel fuel. When your 6.4 undergoes active regeneration, diesel is injected late in the exhaust stroke. It then travels into the exhaust stream, elevates EGTs and burns off hydrocarbons from the diesel particulate filter.

Oil dilution is an unfortunate by-product of this emissions process. What problems can oil dilution lead to though? Diesel doesn’t offer the same lubricating properties as your engine oil does. This can lead to increased wear and tear on crucial engine components because of a lack of lubrication. So how do you prevent this problem from happening?

The Fix For Oil Dilution

First and foremost, check your engine oil frequently. Once a week take a look at your dip stick. If you’re over max oil capacity, change the oil and oil filter immediately. Don’t use the 10,000 oil change intervals recommended by your owner’s manual. Instead, change the oil and filter on your 6.4L Powerstroke every 5,000 miles. Also make sure you use high quality oil that meets or exceeds OEM specs. If you’re over 5,000 miles, here are some high quality 6.4L Powerstroke engine oils and oil filters that you can use to do maintenance immediately.

6.4L Powerstroke Engine Oil : Motorcraft 15W-40 Diesel Motor Oil

Motorcraft SAE 15W40 Diesel engine Oil

Can’t go wrong with OEM when it comes to maintenance. One of the best 6.4L Powerstroke engine oils to use is Motorcraft 15W-40 Diesel Motor Oil. This is the preferred engine oil viscosity for climates above 20 degrees Fahrenheit. If you are in a colder climate, your truck may require a different viscosity. Check your diesel supplement manual or your owner’s manual for more information.

Motorcraft FL-2016

Motorcraft Filters are the ONLY filters you should ever use in your Powerstroke diesel truck. The 2008-2010 6.4L Powerstroke uses the Motorcraft FL-2016 engine oil filter which provides OEM quality filtration and reliability.

On trucks that aren’t used on the highway or are strictly used for off-road fun or competitions like sled pulling, deleting the DPF altogether is possible. Deleting your engine’s Diesel Particulate Filter stops regeneration from ever occurring in the first place. It requires the use of a straight pipe exhaust system and a delete-capable tuning device.

2. Leaking Radiators

Unlike the 6.0L Powerstroke, a puddle of coolant underneath your truck isn’t because of a blown head gasket. 6.4L Powerstrokes are notorious for developing radiator leaks because of the poor radiator design. The crimps on the plastic ends of the radiator tend to separate, causing them to leak. When you’re losing coolant, you’ll often experience overheating which could lead to major problems if not addressed as soon as possible. You might also notice visible signs of the radiator leaking.

The Solution for a 6.4L Powerstroke Leaking Radiator

Unfortunately, there isn’t a fix for this other than replacing the radiator. Even if your stock radiator hasn’t failed yet, it’s a good idea to be proactive. Here are some quality 6.4L Powerstroke radiator solutions.

6.4L Powerstroke Mishimoto Aluminum Radiator

Mishimoto 6.4L Powerstroke Radiator

Want to replace that old, leaky radiator that’s currently on your 6.4L Powerstroke? Mishimoto’s 6.4L Powerstroke Aluminum Radiator offers significantly improved durability because the end pieces are completely welded. This radiator also uses rubber mounting begs, instead of the solid metal OEM ones, to reduce the amount of flex force transferred to the radiator.

To further increase radiator durability, you can also get a radiator support bar. Radiator support bars add rigidity and help prolong coolant system life by reducing front end flex and twisting. Here’s a high-quality radiator support bar you should consider.

Mishimoto Radiator Upper Support Bar

Mishimoto’s Radiator Upper Support Bar helps prevent one of the most common 6.4L Powerstroke Problems. It adds some much needed rigidity to your radiator and reduces the transfer of force and shock to the truck’s radiator.

3. Poor Fuel Economy

Despite the impressive 6.4L Powerstroke specs and features that make these engines a powerhouse, they lack substantially when it comes to fuel efficiency. The major reason for the 6.4’s lack of mpgs is none other than the new diesel particulate filter. Active regeneration uses diesel to increase EGTs and clean the dpf. Unfortunately, that’s diesel fuel being used for something other than propulsion. City driving and driving in heavy traffic make mpgs go down ever further as they will result in more frequent active regeneration cycles.

Making A 6.4L Powerstroke More Fuel Efficient

If you want to improve fuel economy in your 6.4L Powerstroke you’re going to have to spend some money. While a straight pipe exhaust and a tuner will greatly increase your mpgs, deleting or turning off emissions devices is federally illegal on any highway driven or registered vehicle. Instead, you’re going to want to invest in aftermarket accessories like a cold air intake, aftermarket intercooler, and a programmer or tuner that doesn’t delete your emissions devices. Many tuners are now CARB approved and emissions compliant. Here are some of our favorite mods to increase fuel economy.

Air Dog II-4G 100 GPH Lift Pump

Want better fuel economy on your 6.4? What better way to achieve this than by giving your engine cleaner fuel for a more complete burn. Lift Pumps like the Air Dog II-4G 100 GPH Lift Pump System provide significantly better fuel filtration than your truck’s factory fuel filtration systems. They also supply a steady amount of fuel making them invaluable when you add tuning! The factory lift pump often falls short of supply your truck what it needs when a tuner is added, starving your truck’s fuel injection pump. For higher horsepower engines (500-700 hp) use the Air Dog II-4G 165 GPH Lift Pump System instead!

Bully Dog GT Diesel Tuner

The Bully Dog GT Diesel Tuner is a popular 6.4L Powerstroke tuner that offers box tunes as well as data parameter monitoring in one package!

Bully Dog/SCT GTX Monitor & Tuner

If you want custom tunes for your 6.4L Powerstroke, the latest products from SCT and Bully Dog like the Bully Dog GTX offer custom tuning capabilities that can be received over the cloud. That means no hooking up to a computer is required to load tunes onto the device and your truck! Just remember, the device doesn’t come with tunes, you have to purchase custom tunes from a vendor like Innovative Diesel.

For more information on how to improve performance and reliability on 2008-2010 Ford Superduty trucks with a Diesel engine, visit our 13 Best 6.4L Powerstroke Performance Upgrades Post.

4. 6.4L Powerstroke DPF Problems

The primary responsibility of the diesel particulate filter is to capture unburnt hydrocarbons before they exit the tailpipe. While the DPF does this successfully reduce tailpipe emissions on the 6.4, they were the first emissions system of this type ever offered on a Powerstroke Diesel engine. Like any new design, there were a number of common issues found on these early and rudimentary diesel particulate filters.

Common 6.4L Powerstroke DPF Problems Include:

  • Clogging: Over time the 6.4L Powerstroke’s Diesel Particulate Filter can clog. A clogged DPF causes severe restriction in the exhaust system that needs to be resolved immediately. This occurs when the regeneration process fails to properly clean the Diesel Particulate Filter and often in higher mileage engines.
  • Leaking: These early DPFs can leak, even soon after the trucks originally left the dealership.
  • Sensor Failure: Sensors are also prone to failure on the DPF system.

Solutions to DPF Problems

DPF problems are often expensive and require replacement. Leaking or plugged up DPF systems typically require you to purchase a new one. Unlike Semis and Big-Rigs where the DPF system is designed to be lowered and cleaned, these DPFs are not easy to clean. If your OEM DPF has failed, here are some replacement DPF systems for your 6.4L Powerstroke.

Performance Diesel Particulate Filter for 6.4L Powerstroke

Bully Dog Performance DPF

Now discontinued, the Bully Dog Performance DPF offers performance gains while also allowing it to be cleaned.

Alliant Power 6.4l Powerstroke DPF system

Alliant Power DPF

Another replacement DPF system that is available for the 6.4L Powerstroke is the Alliant Power DPF.

5. Cracked Up-Pipes

Is your 6.4L Powerstroke experiencing excessive soot in the engine compartment? Is there soot on the firewall or the hood area? Can you hear a loud hissing noise from under the hood? A very common issue with the 6.4 is cracking up-pipes. The cracking occurs on the expansion joints and can cause a huge loss of power, as well as the symptoms listed above.

Solution to Cracked Up-Pipe Expansion Joints

Unfortunately, your only option with cracked up-pipes is to replace them. Don’t go with another set of factory up-pipes though! There are plenty of aftermarket up-pipes that offer superior construction and even life-time warranties. Check out these quality aftermarket up-pipes that should solve the problem forever!

Rudy’s Diesel Thick-Wall HD Up-Pipes

Want heavy duty stainless steel replacement up-pipes for your cracked OEM ones? Rudy’s Diesel Thick-Wall Up-Pipes are a direct OEM replacement and even EGR compliant!

MBRP Aluminized Up-Pipes

MBRP’s Up-Pipe Kit replaces the problematic OEM up-pipes while retaining EGR compliance! They’re a direct OEM replacement too!

6. Clogged EGR Coolers

The 6.4L Powerstroke’s EGR Coolers reduce the temperature of hot exhaust gases after they are re-routed by the EGR valve. Coolant is used in this process which over time can break down, clogging the EGR cooler. Similar to the 6.0L Powerstroke, 6.4s experience EGR Cooler failure often. Unfortunately, the 6.4L Powerstroke uses two EGR Coolers instead of just one. That’s two EGR Coolers than can fail! That’s twice the headache!

Preventing Clogging EGR Coolers

As a preventative measure, invest in a coolant filtration system. Coolant breakdown is an inevitable part of the exhaust gas recirculation process. Coolant filtration systems help preserve your coolant quality and can drastically increase coolant lifetimes. Mishimoto and Sinister Diesel both make relatively cheap coolant filtration systems.

Mishimoto Coolant Filtration System 6.4L Powerstroke

Mishimoto Coolant Filtration System

Mishimoto’s Coolant Filtration System is probably the best quality system on the market. Mishimoto specializes in performance cooling applications and this kit will preserve your coolant quality and it’s also pretty easy to install!

Sinister Diesel Coolant Filtration System

Sinister Diesel’s Coolant Filtration system will also preserve your 6.4L Powerstroke’s coolant quality and extend coolant change intervals.

Make sure you also follow a severe 6.4L Powerstroke maintenance schedule too. By changing your coolant frequently, you maintain high-quality coolant flowing throughout your 6.4L Powerstroke’s cooling system. Aftermarket EGR Coolers can also offer superior performance and durability compared to factory ones.

Fixing a Plugged EGR Cooler

If one, or both, of your OEM EGR Coolers has already plugged up, you can replace them with aftermarket units that are significantly more durable and reliable. Aftermarket coolers often feature a sturdier design to prevent leaking and improved coolant flow to help lower coolant temperatures. Check out these EGR Cooler replacement systems for the 6.4L Powerstroke.

BulletProof Diesel EGR Cooler Kit

Bulletproof Diesel’s EGR Cooler Kit is arguably the most popular and highest quality EGR Cooler kit available.

AFE Bladerunner EGR Combo

AFE Power’s Bladerunner EGR Combo is another aftermarket replacement kit for your factory 6.4 Powerstroke EGR Cooler System.

7. High Pressure Fuel Pump Wire Chafing

Early model year 6.4L Powerstroke are susceptible to chafing on the high pressure fuel pump harness. Over time, vibrations can cause the wires to be exposed. Once exposed, you run the risk of shorting your high pressure fuel pump. That’s an expensive repair you don’t want to risk! Luckily there is an easy solution.

Solution

Later model 6.4 Powerstroke engines don’t seem to encounter this problem as frequently. Ford was well aware of this problem. They corrected this problem in late model trucks by adding a protective covering to the wire harness. This is one of the reasons later versions of the 6.4L Powerstroke are more desirable than early ones. If you haven’t purchased one yet, look for a 2009-2010 model.

If it’s too late and the wires on your HPFP are exposed, purchase Ford’s replacement harness Ford Part # 8C3Z-9G805-B. It’ll come with a protective covering so you won’t have the same problem again. Unfortunately, this repair requires the cab to be pulled. The K16 injection pump is hidden and to get access it requires a ton of work.

Ford # 8C3Z-9G805-B

8. Front Cover Cavitation and Leaks

Front cover leaks can develop overtime, which can cause coolant to leak into the crankcase. This is another reason it is very important to check your dipstick frequently. You can often catch a problem before it leads to a total engine rebuild. Frequently, leaks develop near the water pump area. Many believe these leaks occur due to cavitation.

Solution

If you have a front cover leak, you will have to replace it. It won’t be a cheap repair either. The best thing you can do is be vigilant about your 6.4L Powerstroke’s maintenance. Get a coolant filtration device. Invest in quality coolant and the proper SCA/DCA coolant additive. Make sure you change your 6.4L Powerstroke’s coolant as recommend for the manufacturer or even earlier.

9. Fuel-Water Separator Problems

Add one more line item to your list of common 6.4L Powerstroke problems! The fuel-water separator can clog if you don’t drain it frequently enough. Basically the water and diesel fuel mixture coagulates and creates a sludge that can cause the drain valve to stick shut. When enough water is collected it can enter the vehicles fuel system, causing rust and poor fuel quality.

The high pressure fuel system used in these trucks are extremely susceptible to fuel system failures from poor fuel quality. When rust or poor fuel get to the fuel injection pump, it can lead to self-destruction of the K16 injection pump which then sends metal shrapnel to your injectors. This can essentially kill the entire fuel system costing thousands and thousands of dollars of repair and a truck that is in the shop for a long time.

Solution

The best way to prevent fuel system failure resulting from the OEM Water/fuel separator is to drain it frequently. The more frequently, the better. If you need to, drain it every other week. This should help maintain the factory system for longer.

Another solution to greatly improve fuel quality and extend fuel system lifetimes is by installing a fuel lift pump system. They offer superior fuel filtration than the OEM system and the result is greater fuel economy, fuel system longevity, and even better performance. Here are some quality kits!

Air Dog II-4G 100 GPH Lift Pump System

For stock to slightly modified trucks, the Air Dog II-4G 100 GPH Lift Pump system provides a consistent supply of fuel and better fuel filtration characteristics than the OEM fuel system. The result is long fuel system life and better overall performance.

6-4l-powerstroke-lift-pump-air-dog

Air Dog II-4G 165 GPH Lift Pump System

If your truck is more than a little modified and you fall in the 500-700 horsepower range, you need the Air Dog II-4G 165 GPH Lift Pump System. This system is designed to work with trucks that require a little more fuel.

10. Clogged Engine Oil Cooler

Many EGR related failures are actually mis-diagnosed. The real problem you may be encountering is a clogged Engine Oil Cooler. Clogged Engine Oil Coolers is another frequently encountered 6.4L Powerstroke Problem in which coolant breakdown blocks the passages of the Oil Cooler. The Oil Cooler is responsible for cooling your 6.4L Powerstroke’s engine oil by using coolant. When these passages get blocked up your 6.4 will experience higher engine oil temperatures, less coolant flow to the EGR system, and the engine can often derate.

You can often spot an engine oil cooler that isn’t working properly by monitoring your engine’s coolant and engine oil temperatures. If there is more than a 14-degree split between the two, it’s likely that your engine oil cooler is on its way out.

Fixing 6.4L Powerstroke Oil Cooler Problems

Unfortunately, the 6.4L Powerstroke oil cooler isn’t able to be cleaned. Instead, you have to replace it. You can replace it with a Ford OEM engine oil cooler which will likely solve the problem for another 50-75,000 miles or you can use an aftermarket engine oil cooler. Aftermarket engine oil coolers often last longer and provide better cooling performance than OEM units. Adding a coolant filtration system like the Mishimoto Coolant Filtration system above is a great way to improve oil cooler lifetimes as well.

Ford OEM Oil Cooler

If you like OEM replacement parts, the OEM Ford 6.4L Powerstroke Oil Cooler should give you another 50-75,000 problem-free miles when you replace your old broken one.

Mishimoto Oil Cooler

Want an affordable, highly-rated 6.4L Powerstroke oil cooler for a great price? Mishimoto’s 6.4 Powerstroke Oil Cooler offers a ton of value at less $200 and comes with a lifetime warranty!

Alliant Power Oil Cooler

Another quality replacement Oil Cooler that will get the job done is the Alliant Power Oil Cooler.

11. 6.4L Powerstroke Cracked Piston Problems

The 6.4L Powerstroke is known for cracking pistons. It typically happens in higher mileage engines, but this is can affect all-mileage 6.4 trucks. If left unchecked even bigger issues can occur, like melted injector tips.

Piston cracking is a result of poorly designed pistons that aren’t very durable. The OEM pistons feature a fuel bowl, which is where the cracks typically start at the thin edge. Then these cracks typically develop and get worse. This crack can then lengthen across the entire piston.

Fixing 6.4L Powerstroke Piston Problems

Unfortunately, replacing your 6.4L Powerstroke engine’s pistons is a very expensive repair which requires engine disassembly. Replacing the OEM pistons with MaxxForce pistons seems to do the truck. The International MaxxForce 7 engine was used on heavier duty commercial vehicles and therefore was built slightly better. The pistons used on the MaxxForce 7 don’t feature the thin lip that causes piston cracking, making them significantly more reliable than those found on the 6.4l Powerstroke.

It’s Not All Bad

While the 6.4L Powerstroke looks like its not worth the trouble, there are many people who swear by these trucks and love them. The 6.4L Powerstroke has impressive performance specs thanks to its twin sequential turbochargers and common rail fuel injection system. Over 500 horsepower can easily be achieved inexpensively.

This propensity to become powerful can lead to headaches down the road however. Increasing performance often shortens any engine’s lifespan. It’s best practice to limit modifications that improve performance to unsustainable levels. Proper, frequent maintenance is also strongly encouraged. Treating this engine like the reliable and trusty 7.3L Powerstroke will result in a very short lifespan.

Check out our Comprehensive 6.4L Powerstroke Maintenance Guide for detailed information about how to maintain these trucks. It covers recommended maintenance intervals and also lists the parts, fluids, and filters you need to keep your 6.4 on the road!

Other 6.4L Powerstroke Resources

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ABOUT Kamil

Founder of Diesel Resource and a complete diesel head. Has a little bit of problem buying too many trucks. Learn more about him by checking out his truck.