Many class action lawsuits have resulted from the numerous problems that arose frequently. There are many claims that the early 6 liters were the most problematic, though it is debatable if there truly is any significant correlation between model year and reliability. A common perspective, in which we support, is that the 6.0L and its problems were hit and miss. The engine is undoubtedly more temperamental than diesel owners expected. The good news is that most trucks on the road today have received adequate repair and/or have received updated parts, and therefore are less prone to future failures. The problems typically arose quickly, early on in the engine's life cycle, and therefore the trucks on the road today are much more reliable than they were coming off the assembly line. We hope the following information helps current 6.0L Power Stroke owners and prospective buyers better understand, diagnose, and prevent reliability issues.
Note: problems are not listed in any particular order of frequency or significance.
TTY Head Bolts
The 6.0L Power Stroke cylinder heads and secured to the engine block via TTY (torque to yield) head bolts. TTY bolts are a one time use fastener; once they are stretched during the assembly process, they must be replaced if they are removed. From an engineering standpoint, the head bolts are sufficient for there application. In a completely stock engine, their reliability is not of major concern. In applications where performance has been increased via aftermarket components, cylinder pressures may rise beyond the limits of the head bolts, ultimately causing head gasket failures. Additionally, the EGR system has been known to contribute to engines to run hotter than expected, which may lower the yield point of the head bolts and in some situations even warp the cylinder heads. The solution is to install aftermarket head studs, which offer more desirable material properties and evenly distributed clamping force. If any performance modifications are to be performed, head studs and new head gaskets are highly recommended.
EGR Valves & EGR Coolers
6.0L Power Stroke EGR (exhaust gas recirculation) valves and EGR coolers commonly fail and/or contribute to reliability concerns. The EGR valve is an emissions device that controls the amount of exhaust gases that are reintroduced into the engine, essentially diluting the intake charge to reduce NOx emissions. The EGR cooler is responsible for cooling exhaust gases before they are reintroduced. It is essentially a heat exchanger, in which coolant and exhaust gases flow through. The EGR cooler is responsible for higher than ideal operating temperatures, especially under load.
Both are prone to failure, the common culprit being soot buildup. When soot builds up in the EGR cooler, it can become clogged and the excessive heat can boil coolant in the exchanger. The EGR coolers have also been known to fail and leak coolant into the exhaust system (white smoke is typically noticed coming from the exhaust, which is steam). 2003 model year Power Strokes have a round EGR cooler, which is less prone to failure than the less efficient square cooler found on 2004 to 2007 model year engines.
The EGR valves may build with soot and cease to function. If the valve sticks in the open position, a loss of power may be experienced. Excessive carbon buildup on the EGR valve is extremely common on every model year 6 liter. Poor fuel quality and excessive idling will contribute to EGR clogging. Clean the EGR valve at every other oil change to keep it functioning properly. If your engine's oil cooler fails, consider upgrading to an aftermarket unit, or replace your 2004-2007 MY cooler with a 2003 MY unit.
Oil Cooler Failure
Replacing the oil cooler on a 6.0L Power Stroke is an expensive operation. Residual sand not removed from the cooler after being casted contributes to clogging of the coolant side of the cooler. Poor oil quality can also clog the oil side of the cooler, and occasionally the oil cooler gaskets have been known to fail. An oil cooler failure is suspect if oil is present in the coolant or visa versa. To reduce the chance of failure, change your engine oil and coolant at Ford's recommended intervals. You may also consider investing in an aftermarket coolant filter to remove particulates from the engine cooling system.
6.0L Power Stroke FICM Failure
The FICM (fuel injection control module) resides on the driver side valve cover of the 6.0L Power Stroke. The FICM is an electronic component, and is bound to "burn up" at some point. However, engine heat and vibration is known to contribute to premature FICM failures. FICM failures are responsible for a number of rough running, no start, hard start, and stalling conditions. They can be tested and if it needs to be replaced, consider having it professionally rebuilt from a company whom offers a warranty on their repairs. There are a number of options out there and many of the rebuilds are of higher quality than the originals.
ICP & IPR Sensor Failures
The ICP (injection control pressure) sensor relays oil pressure in the high pressure oil rail. The IPR (injection pressure regulator) is located on the back of the high pressure oil pump and controls pressure in the high pressure oil system. Both sensors have been known to fail prematurely. To the best of our knowledge, the replacement ICP and IPR (from Ford) are upgraded components and not as problematic.
Sticking HEUI Injectors
HEUI (hydraulically actuated electronically controlled unit injector) injectors rely on high pressure oil to pressurize fuel in the injector body, as opposed to utilizing a high pressure injection pump. In a simplistic model, an oil pump pressurizes engine oil and sends it to the injector, and a piston/plunger in the injector uses the oil pressure to pressurize fuel before it is injected into the engine's cylinder. HEUI injection systems were advanced when they were introduced by Caterpillar in the 90's, but have since been replaced by common rail technology. The injectors are sensitive to poor fuel and oil quality. The best thing you can do to prevent failure is maintain proper fuel quality (by means of an additive if necessary) and keep your engine oil changed regularly. The 6.0L injectors in particular are prone to stiction; there are several additives on the market that prevent and in some rare cases even reverse stiction problems in these injectors. Archoil is amongst the leading manufacturers of stiction eliminating oil additives.
High Pressure Oil Pump Failure
The Power Stroke HPOP (high pressure oil pump) is a swash plate style pump that pressurizes engine oil to more than 3,000 psi. The high pressure oil is used compress fuel in the injectors. The HPOP on the 6.0L Power Stroke has been known malfunction; from leaking seals to complete failures. It's worth noting that the pump is considered a wear item and is expected to need to be replaced at some point regardless. However, the 6.0L pumps are notorious for needing replacement sooner than expected. Electronic diagnostic equipment can be used to verify whether or not the pump is operating within spec. At wide open throttle with a load (i.e. driving), oil pressure (in the high pressure system) should read between 3,000 and 4,000 psi. At idle, oil pressure is typically in the 600 - 700 psi range. A minimum of 500 psi is required to fire the injectors; if pressure drops below that, the engine will stall.
Turbocharger Lag, Sticking VGT Vanes, Turbocharger Failure
The 6.0L Power Stroke is equipped with a VGT (variable geometry turbocharger) that uses a series of mechanisms called vanes to increase/decrease the effective volume of the turbine housing. The result is a more efficient turbocharger design with decreased spool times and overall better operating characteristics. Unfortunately, the VGT vanes can become clogged with soot and stick in the open position. When this occurs, throttle response will suffer and the turbocharger will take more time to spool. There are 2 solutions, the first of which is to remove the turbocharger and thoroughly clean the vanes. The second, and much easier method is to run the truck flat out for a short period of time. Running at WOT sometimes works the turbo hard enough to clear any build up. 2003 to 2005 model year engines also suffer from an insufficient oil drain tube. This can result in oil cooking in the turbocharger, and has been known to cause complete turbo failure in some instances. 2006 and 2007 model year engines received an upgraded oil drain tube to solve this problem, and 2007 model year engines had a revised oil passage to further reduce the chances of turbo failure.
Wire Harness Chafing
The root cause of many hard start, no start, and electrical issues is chafing of the wiring harness. Simply put, wires vibrating against brackets, corners, or components that they are secured to wear down their lining and ground out when they come into contact with something conductive. Search for wire chafing by following the wires, paying close attention to points where the harness and/or wires are secured tightly to something.
Oil Rail & Plug Leaks
O rings used to seal oil plugs in the high pressure oil rail/system commonly fail on the 6.0L Power Stroke. This can cause the engine to run rough, stall, or have a no hot start condition, often with trouble codes P2284, P2290 or P2291.
6.0L Power Stroke & Performance Add-ons
A large portion of the 6 liters that have major problems have been modified. If any tuning or programming modifications are to be performed, head studs are highly recommended. At this level of performance, it's not a question of if, but when, the TTY head bolts are going to fail. Blown head gaskets are extremely common in modified engines. Additionally, consider deleting the EGR system. Structurally, the 6.0L Power Stroke can manage much more power than stock, save for the factory head bolts.
6.0L Power Stroke Coolant Leaking
If the EGR cooler and oil cooler are not to blame for disappearing coolant (assuming you do not have a blown head gasket), check the degas bottle, they have been known to crack at the seams.