Make That Dirt-Cheap 6.0L a Reliable Daily Driver

They’re cheap for a reason. They’re nothing but problems. They’re junk.

We’ve heard it all before. These words of warning are common for any prospective buyer of a used 6.0L Power Stroke. After all, the Navistar-built V8 offered in ’03-07 Ford Super Duty’s, was plagued with a slew of design flaws from the very beginning. Some items on the laundry list include fuel injection problems, cooling and emissions systems error, and the lingering concern for potential gasket failure. However, there’s something about paying $10-12k for a low-mile, four-wheel-drive, crew cab diesel that continues to lure people in.

Even with all the 6.0L’s shortcomings, most of the failures can be averted by performing proper maintenance. This includes observing Ford’s “severe duty” oil change interval of 5,000 miles, running a synthetic and lower viscosity oil for better cold weather performance, and ensuring you change both fuel filters every 10,000 miles. After comparing multiple brands, we highly recommend you stick with Motorcraft filters (PN FD-4616). Additionally, if you leave the EGR system untouched, make sure you test your coolant every 15,000 to 20,000 miles. By using coolant to drop exhaust gas temperatures from 1,400 to 350 degrees, the 6.0L’s EGR system is very tough on coolant.
First thing’s first—plan on monitoring engine coolant and engine oil temperature to see if an oil cooler repair is needed. Engine oil temperature should stay within 15 degrees of coolant temp when the engine is up to operating temp. Anything beyond the 15-degree range and it’s likely time for a new oil cooler or equivalent. Oil cooler failure is one of the most common problems on a 6.0L. The stacked-plate heat exchanger is notorious for plugging up on the coolant side, thereby superheating the engine oil and sometimes even taking out the EGR cooler in the process. Such a bypass would result in increased performance but at the expense of emissions testing failure and engine deposit buildup.
The EGR cooler faces failure on two fronts. First, when the aforementioned oil cooler plugs up and stops the flow of coolant through the EGR cooler the extreme heat can cause it to crack or burst along the welds. Second, due to the EGR cooler routing spent exhaust gases back to the intake manifold, the constant exposure to soot leads to accumulation. This buildup of soot, carbon and grime eventually hampers internal flow, leading to excessive heat, which can (once again) cause the EGR cooler to rupture. When the EGR cooler cracks, coolant is allowed into the engine’s exhaust or intake and the problem is often misdiagnosed as a blown head gasket.
Never repeatedly replace a 6.0L’s EGR cooler without digging deeper. More than 90 percent of all EGR cooler failures are caused by a clogged oil cooler blocking coolant flow to it. This is precisely why most reputable shops install a new oil cooler any time the EGR cooler is replaced.
In an effort to give exhaust gases more travel time before passing through the EGR valve on their way into the intake manifold, Ford added a longer EGR cooler to the 6.0L starting on ’04.5 models (left). However, its square-tube design ended up being more prone to soot accumulation (and ultimately failure) than the circular unit used on ’03 to early ’04 engines. Per the folks at Bullet Proof Diesel—a company that offers emissions-compliant, direct-fit replacement and ultra-reliable EGR coolers for the 6.0L—the square, late-style EGR cooler was added to engines built on or after September 22, 2003.
Another emissions system component that’s prone to plugging up, sticking and failing is the EGR valve. Once through the EGR cooler, the EGR valve meters the amount of cooled exhaust gases introduced into the intake tract. Like the EGR cooler, the valve is constantly exposed to a mixture of soot and blowby, which culminates in an impenetrable buildup of grime that hinders the component’s operation. If you plan to leave your 6.0L’s EGR system intact, make it part of your maintenance regimen to remove and clean your EGR valve on a regular basis. They can begin to stick and even seize in as little as 20,000 miles of use.

To be sure, the problems associated with the 6.0L Power Stroke have been extensively documented. However, there are some situations where buying a cheap diesel-powered ’03-07 Ford can pay off. The key is whether or not you’ve got the mechanical experience to make (and keep) one reliable. If you adhere to a strict maintenance schedule, know how to diagnose a problem when it arises, and you’re no stranger to turning a wrench, you can all but eliminate the bulk of the costs involved in keeping a 6.0L on the road.

Don’t believe us? Keep reading for a list of the 6.0L’s most common failure points, along with how they can be fixed or upgraded. You might just find that the 6.0L isn’t half as bad as you were led to believe.

The most affordable way to combat oil cooler failure is by eliminating debris from the engine’s coolant. This can be accomplished by installing a coolant filtration system, which will run for $170 or less. These bypass-style filtration systems filter a small amount of coolant at a time and remove casting sand, sediment, and suspended solids from the coolant circuit. With the engine coolant free of debris, both the oil cooler and EGR cooler will live much longer. For less than $200 this is one of the most affordable insurance items you can add to a 6.0L Power Stroke.
Stuck turbo scenarios run amok in the 6.0L segment. The problem is most prevalent on trucks that see a lot of idle time or steady-state driving, where the vanes in the turbine side of the variable-geometry Garrett turbocharger aren’t regularly exercised. In most cases the unison ring is the culprit (shown above) and a P0299 code is thrown by the PCM. The unison ring is the part that physically moves the vanes, effectively controlling exhaust flow to the turbine wheel. When it seizes in place (due to carbon accumulation and rust), and depending which position the vanes end up in, the truck will either have great low-rpm response but no top-end power, or extreme lag down low and adequate power up top. Having the proper scan tool to monitor VGT cycle is a great way to determine whether you’re dealing with a stuck vane situation.
Most sticking turbo issues can be solved by pulling the turbo apart and treating it to a thorough cleaning via a Scotch-Brite pad and die grinder. However, in cases where extreme wear, corrosion and even a damaged turbine wheel is present (such as in the image shown here), turbo replacement may be the only option.
Because the variable geometry aspect of the factory turbocharger relies on an exhaust backpressure (EBP) sensor, keeping the tube (shown above) that spans from the driver-side exhaust manifold to the EBP sensor free of soot is paramount if you want your turbo to function properly. If the tube plugs up, backpressure values being reported to the PCM are inaccurate. And being that the PCM controls the actuation of the variable vanes in the exhaust side of the turbo based on that feedback, the VGT’s performance will be hindered, even erratic.
While many folks tend to associate the 6.0L with all kinds of injector issues, it’s not always the case. Aside from lack of maintenance, improper installation (in which the O-rings are damaged or the hold-down is over-torqued) and old age, the primary cause of injector issues boils down to stiction. This process occurs when carbon deposits and oil coking form inside the injector and cause the spool valve to experience friction. Because the spool valves are used to allow high-pressure oil into the top portion of the injector to fire the fuel side, a sticking valve makes for inefficient operation.
Beyond fuel contamination and stiction, low fuel pressure is a major killer of injectors. Don’t neglect fuel filter changes until the filters are clogged. If you have to buy an injector or two, make sure you buy units that have new nozzles, coils, spool valves and plungers like Motorcraft injectors do. Trust us—in this case the higher price you pay correlates to a higher quality product.
It’s often said that the 6.0L’s use of only four head bolts per cylinder, in which two fasteners share their clamping force with the next cylinder, isn’t enough to keep the head gaskets alive. We beg to differ. Granted, six bolts per cylinder would’ve been nice, but instead of it being a problem of a lack of fasteners, we believe the diameter of the bolt has a lot more to do with it. After all, the 6.4L Power Stroke made use of four head bolts per cylinder and kept head gaskets alive at power levels in the 600-rwhp range—and with compound turbocharging in the mix! The difference? The 6.4L made use of 16mm head bolts whereas the bolts used in the 6.0L measure 14 mm.
Blown head gaskets? Not so fast. Although the head bolts are known to stretch and head gasket failure is common on these engines, unless you know for sure that a gasket is blown, don’t pull the heads. Reason being, a ton of used trucks are “diagnosed” with blown head gaskets only to have the problem traced back to a plugged oil cooler, cracked EGR cooler, a faulty degas bottle cap, a coolant drip from a radiator hose, or a plugged heater core.
Other than machine shop costs and forking over the cash for studs, new head gaskets, miscellaneous O-rings, seals, and gaskets, you can save a lot of money by performing a head gasket job yourself. However, it’s not uncommon to find cracks in the heads once they’ve been pulled. Oftentimes cracks protrude into the exhaust valve seats, rendering them unusable. Trucks that have seen a lot of abuse (i.e., high EGT) are usually most susceptible to cracking, but we’ve seen plenty of lightly worked trucks experience cracked heads as well. It’s typically hit or miss as to whether or not your engine will need new heads, but it’s a potential cost you’ll want to factor into the project, once you start tearing down the top end.
With some folks driving around on a blown head gasket for quite some time before unloading their truck at a dealer or through a private sale, it’s vital that the heads be checked by a trusted, reputable machine shop. Even if your heads are crack-free, they may still be warped. If they’re warped beyond 0.004 inches in any one area across the head’s surface, it’s considered by Ford to be unusable.
While the deck surface of the 6.0L block tends to remain true, it’s worth checking it for flatness before you install the resurfaced heads. If you find more than a 0.002-inch difference across any 5.9-inch area along the block, it shouldn’t be reused. Luckily, warpage on the block is much rarer than on the head.
During your block prep, take care to only remove what’s left of the original head gasket and don’t remove material from the block itself. Choose a mild Scotch-Brite pad over an aggressive one, and use a die grinder (you won’t get very far by hand). After that, make sure each head bolt hole is free of oil, coolant and debris, and chase the threads if you feel the need.
If you’re looking to buy a ’04.5-07 Super Duty, this may be one of the first things you have to address. The snap-to-connect (STC) fitting connects the branch tubes to the back of the high-pressure oil pump. Due to branch tube flexing, excessive wear occurs on the STC fitting’s seal, which develops into a high-pressure oil leak and eventually, complete separation of the two-piece fitting.
A truck that cold-starts fine but won’t restart once warm, is a telltale sign of STC fitting failure. This is because cold oil won’t leak past the bad seal, but warm oil will. With the thinner, warm oil slipping by the seal, the HEUI system can’t build enough injection control pressure (ICP) to restart the engine. Ford’s update kit (PN 4C3Z-9B246-F) replaces the STC fitting with a threaded fitting similar to what was found on ’03 and early ’04 engines, and the kit retails for roughly $60.
High-pressure oil leaks are fairly common on the 6.0L, so it conditions you to be able to track down any leak you encounter. The best way to pinpoint a leak is with compressed air. Most 6.0L techs and gurus ensure the IPR valve is completely closed, pull the ICP sensor, and shoot compressed air into the ICP sensor port to determine the location where the air is escaping the high-pressure oil system. We’ve seen the method used to trace a leak back to one of the O-rings on an oil stand pipe in the past (the one shown being from an ’04.5-07 engine). The oil stand pipes link the oil branch tubes with the oil rails.
Premature O-ring failure is also fairly common on the dummy and oil supply plugs in the high-pressure oil rails. The dummy plugs are located at the front of the oil rails, while the oil supply plugs can be found at the rear of the rails. Textbook signs of a high-pressure oil leak include long crank but no start scenarios, low ICP, surging under acceleration, the engine cold-starts fine but won’t restart once warm, choppy idle once warm, high IPR duty cycle, and low power.
Due to its direct tie-in with your batteries, a fuel injection control module (FICM) will always die a slow death, but will typically enter stress in colder weather. On a 6.0L, the FICM sends the 48-volt signal that’s required to fire each injector as precisely and efficiently as possible. Unfortunately, without proper voltage being sent to the FICM (i.e., weak batteries) the FICM becomes damaged and in turn begins sending less than 48 volts to the injectors. As a result, startups, overall performance, and fuel efficiency all diminish. Once cold weather arrives you’re met with hard-starting, rough idling and even low voltage codes. With the engine keyed on, cranking over and running, FICM voltage should always be between 45 and 48 volts.
No other engine’s performance depends on its charging system quite like the 6.0L Power Stroke’s does. Unless you enjoy replacing (or repairing) FICMs, it pays to ensure your batteries (and alternator) remain in tip-top shape. That means if they’re a couple years old, have them load tested or replaced. If the truck is still on its original alternator, get it tested or replaced as well. For preparatory measures, never wait until your batteries are dead before replacing them.
Just like a 7.3L Power Stroke, the 6.0L utilizes an ICP sensor to keep tabs on high-pressure oil in the rails. On ’03 and early ’04 engines, the 5-volt sensor is located in the high-pressure oil pump cover at the rear of the lifter valley, underneath the turbocharger’s up-pipes, and facing the driver’s side of the truck. It’s rumored that the ICP sensor fails more frequently on these engines compared to later versions due to exposure to excessive heat. If you’re looking at an ’03-04 Super Duty that you suspect has a rear main leak, check the ICP sensor first. Relocated midway through the ’04 model year, the ICP sensor can be found in the right-front high-pressure oil rail on ’04.5-07 trucks.
Instead of relocating the injection pressure regulator (IPR) in mid-2004, Ford added a removable heat shield for added protection from the heat given off by the up-pipes. While the IPR is known to live a fairly lengthy life in a 6.0L application, the perforated plate edge filter on the end of each unit can tell you if a potential catastrophe is on the horizon. If you discover metal or debris on the IPR filter screen, something passed through the high-pressure oil pump. If the screen is gone, something made it into the IPR.
We know it’s not engine-related, but there’s no denying the durability of the 5R110 TorqShift. As long as it’s been maintained and not overly abused, the five-speed automatic is one of the best transmissions to ever grace a heavy-duty pickup. We’ve seen low-mile TorqShifts hold up to 190cc injectors, bigger variable-geometry turbos and more than 550 rwhp (1,000 lb-ft of torque) before slipping the factory converter.
Even though the 6.0L Power Stroke engine is an obvious “on-the-fence” item for any potential buyer, let us remind you that the ’03-07 Super Duty trucks themselves are solid. Above average even. And if you happen to find a deal on an ’05 or newer Super Duty, you get the smoother ride of the coil spring, radius arm front suspension, a stouter frame and added towing and payload capability over the ’03-04 versions.




Diesel Tech

Neal Technologies


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