The Navistar 6.0L Powerstroke was released in model year 2003 as a replacement for Ford’s 7.3L Powerstroke,. The 6.0L was to comply with new, stricter EPA emissions standards for light duty diesel trucks in North America. Also, the 6.0L was Ford’s attempt to compete with the higher-horsepower diesels offered by Dodge and Chevrolet/GMC which had both distanced themselves from the relatively limited performance of the 7.3l Powerstroke.
Despite the efforts of Ford and International/Navistar, the 6.0 Liter has shown significant reliability issues. These problems can be very costly to repair, and should ideally be dealt with prior to failure. If owners of a 6.0l proactively upgrade a few problem systems, and make sure to perform maintenance beyond manufacturer specifications, the 6.0L Powerstroke can be a very reliable 500HP daily driver which can deliver very respectable MPG numbers.
The Issues There are several system design issues with the 6.0L Powerstroke. The most frequent of these include EGR and engine oil cooler failure, which cause head gasket failures. Other common reliability issues include variable-geometry turbo (VGT) issues, fuel-injection control module (FICM) failure, and fuel injection system failures, among others.
It is very important to note that the 6.0L engine has proven to be significantly more reliable in its original application, powering medium-duty International trucks. This can be attributed to significantly lower-horsepower tunes, as well as a more open engine compartment, which allows for better airflow through the radiator and better heat dissipation from the engine. The cause of all of the reliability issues with this engine are a direct result of inadequate testing be Ford/Navistar engineers with the release of the 6.0L in light duty diesel trucks. Production was rushed to keep up with the EPA mandates, and essentially Ford used the buying public to test out their new systems.
Engine Oil Cooler Issues The two most common failures of the oil cooler are:
1. Clogging of the coolant passages due to deposits, which form as a result of contaminated or unmaintained coolant
2. Internal leakage between the coolant and oil passages causing a mixture of fluid.
The problem with the engine oil cooler arises when the coolant flows through the tight passageways of the engine oil cooler. The pathways are so small that they catch and stop any large particle suspended in the coolant, blocking the channel. While the units lifetime can vary, it typically takes about 50,000 miles before the coolant can no longer flow through the cooler, stopping it from reaching EGR cooler. This leaves less and less coolant flow and much higher temperature coolant for your engine oil cooler AND for your EGR cooler.
This failure can lead to premature engine wear, blown head gaskets, fuel injector failure and localized overheating of engine components. In the 6.0L powerstroke the engine oil is used not only as a lubricant. The 6.0l also uses high-pressure engine oil is also used to operate the fuel injectors. The oil is also used as a cooling method for engine components such as pistons, adding to the threat of localized overheating. This localized overheating will not indicated by the engine coolant temperature gauge and will probably go unnoticed by the driver, increasing the importance of proper maintenance by a shop like Eisenhart Diesel.
The second of the common engine oil cooler failures, leakage between the coolant and oil passages, is more serious and can lead to severe engine damage. The casting process used for this system was subpar, and resulted in casting sand deposits weakening the fins that separate the oil and coolant. The best way to prevent this failure is to eliminate the stock engine oil cooler completely and replace it with an aftermarket air-to-oil engine oil cooler, rather than coolant-to-oil cooler.
The most noticeable symptom of this type of leakage is usually the presence of oil in the coolant expansion bottle, as well as a milky appearance and consistency of engine oil or coolant due to mixing of the fluids. Since engine oil is under greater pressure than engine coolant, more oil typically enters the cooling system than coolant enters the engine crankcase. This oil contamination causes “sludging” in the cooling system, reducing needed cooling to critical engine parts, causing localized overheating and premature failure of these parts. If left untreated, it can also reduce engine oil level and cause engine failure. Also, if enough coolant enters the crankcase, it can contaminate and dilute the engine oil, removing its ability to lubricate engine components, leading to severe damage to camshaft and crankshaft bearing failures and valve train damage.
EGR Cooler Issues
The 6.0L Powerstroke EGR cooler is mounted below the intake manifold on the right-hand side of the engine, and is prone to rupturing, allowing coolant to leak into the exhaust system. The best way to prevent damage due to EGR cooler failure is to properly maintain or eliminate the stock engine oil cooler, eliminate the EGR system all together.
Common symptoms include steam from the exhaust while driving, as well as coolant loss with no evidence of external leakage. The EGR cooler uses engine coolant to cool exhaust gases, which are reintroduced into the engine’s intake to cool combustion temperatures and reduce nitrous oxide emissions. As you can imagine, the intake systems were NEVER designed to have exhaust gasses passed back trough them. The EGR cooler commonly fails due to overheating and boiling of the coolant inside it, rupturing it and allowing coolant to leak into the exhaust manifold. As the engine oil cooler begins to clog, the EGR cooler is starved for coolant. If the cooler leaks while the engine is not running, coolant can enter engine cylinders through open exhaust valves. Attempting to start the engine after coolant has entered a cylinder can lead to hydrolocking, where the incompressible coolant in the cylinder stops the engine from turning. The affected cylinder’s connecting rod may bend as a result, requiring significant internal engine repairs or engine replacement to correct.
EGR Valve Issues
The 6.0L EGR system uses an electronic solenoid-operated EGR valve with a built-in position sensor. The EGR system recirculates exhaust gases to cool combustion temperatures and reduce the production of oxides of nitrogen. The EGR valve is prone to occasional sticking due to carbon buildup, as well as failure of the position sensor. The best way to prevent problems with the EGR valve is to delete the system completely. The EGR system operates during engine idling, and the low exhaust backpressure present during engine idling means that EGR gases flow at relatively low-speed through the EGR valve. This allows the carbon soot to deposit on the EGR valve, which why the EGR system has to be removed.
Head Gasket Issues
Head gasket failure, AKA as “blown head gaskets,” has proven to be an almost inevitable problem on the 6.0L Powerstroke. The best way to prevent head gasket failure and damage to the cylinder heads is to perform an ARP Head Stud Installation preventively, rather than waiting for a serious problem to arise. When performed preventively, less material can be shaved from the surface of the cylinder heads, and there is less of a chance that cylinder heads will be damaged beyond repair due to head gasket leakage.
Common symptoms of head gasket failure include coolant residue on and around the coolant expansion bottle, and intermittent overheating under heavy load. Head gaskets on the 6.0L leak due to expansion, or stretching, of the stock cylinder head bolts. As the engine heats and cools, the cylinder heads, engine block, gaskets and bolts expand and contract. During periods of high localized heating, such as when pulling a hill under load, the expansion of the cylinder head bolts causes the clamping force they exert on the cylinder head gaskets to reduce to less than that of the force of engine combustion pressures, which breaks the seal between the surfaces. When this happens, combustion escapes from the cylinder head and begins to damage the surface of the cylinder head, engine block and gasket. Combustion pressure leaks into the cooling system, causing coolant to be expelled from the coolant pressure cap, and in the early stages will not cause coolant to enter the combustion chamber. In fact, a 6.0L in the early stages of head gasket failure will usually pass extended cooling system leak-down tests. It is also very common for drivers who only tow with their 6.0L for recreation in summer to notice coolant loss and overheating during a summer trip, and experience no problems all winter until their next trip. This intermittent combustion leak is due to the higher-than-normal combustion pressures and temperatures present when towing.
Now we have identified the main problem areas with the 6.0l Powerstroke. In part 2, Eisenhart Diesel will show you how to remedy these issues and bulletproof your 6.0l!