From plugged oil coolers to injector stiction to sticking turbos, we’ve covered a lot of ground in this series. But we aren’t done yet. High-pressure oil leaks run rampant on the 6.0L Power Stroke, hindering performance and even leaving you with a truck that won’t re-start. We’ll show you the key leak points this time, as well as how to diagnose where the high-pressure oil leak is coming from. Then there is branch tube failure, when oil leaving the high-pressure oil pump is allowed to bleed out of the passage to the heads. Beyond that, there are still the common cracked degas bottle scenarios to contend with (which can cause panic due to coolant loss) and wire chafing problems (which can be hard to diagnose).
Hang on for one last ride down Problem Street. Not all of the following 6.0L Power Stroke problems will sideline you and your truck for a week, but all of them add to this notorious V-8 diesel’s reputation for its failures.
High-Pressure Oil Leak (Stand Pipes)
Knowing how important high-pressure oil is to the overall functionality of the 6.0L Power Stroke’s fuel injection system (HEUI) makes high-pressure oil leaks as serious as a heart attack with this engine. Unfortunately, they are common—and usually due to an inexpensive O-ring. These are the high-pressure oil stand pipes off of ’04-’07 engines (not ’03 models), which link the oil branch tubes to the “wavy” oil rails in the heads. O-rings at both the top and bottom of the stand pipes are notorious for causing high-pressure oil system leaks, be it due to a cut, torn or missing O-ring.
High-Pressure Oil Leak (Rail & Dummy Plugs)
It’s the same song on the rail plugs and dummy plugs in the high-pressure oil rails on ’04-’07 6.0L’s, engines with the wavy rails. The O-rings on these fittings are prone to failure—again, either due to being cut, torn or missing altogether—and kickstarting a leak in the high-pressure oil system. Other common O-ring failures include (but aren’t limited to): a damaged O-ring between the high-pressure oil pump (HPOP) discharge tube and the high-pressure oil pump itself (along with the infamous STC fitting failure on ’05-‘07 engines), the HPOP inlet O-ring, high-pressure oil injector O-ring or a cracked or broken check valve and fitting in the high-pressure oil rail of an early engine (’03 only).
High-Pressure Oil Leak (Cracked Branch Tubes)
We touched on the oil branch tubes—the components that route high-pressure oil from the HPOP to the stand pipes—in Part 8, but we didn’t cover the fact that they can develop hairline cracks over time. It happens due to the constant vibration of the 6.0L engine and when it occurs hot restart problems begin. As engine oil temp increases and the oil viscosity decreases, the leak worsens, and in order to compensate from the oil loss the injection pressure regulator’s (IPR) duty cycle percentage will ramp up. This is usually a dead giveaway that you’ve got a high-pressure oil leak. When the IPR can no longer mask the issue, injection control pressure (ICP) will fall off.
Symptoms Of A High-Pressure Oil Leak
Depending on the location and severity of the high-pressure oil leak, a host of symptoms can surface when a 6.0L develops one. Among them are: long crank time, poor drivability, rough idle when warm, stalling, acceleration surging, lack of power and when things get more serious, high IPR duty cycle coupled with low ICP being maintained. Long cranking and hard hot restarts will soon give way to no starts once sufficient ICP can no longer be built up in order to fire the engine. Commonly stored diagnostic trouble codes (DTC’s) from high-pressure oil leaks include: P2284, P2290 and P2291.
Testing For High-Pressure Oil Leaks
Unfortunately, with any high-pressure oil leak you’re chasing something that’s hidden under the valve covers, so it can take some sleuthing. Per Ford’s shop manual, apply compressed air to the oil rail and first determine that the IPR valve is functioning properly before moving on. Then, by ramping up the IPR’s duty cycle the air leak is isolated between the IPR and oil pan and you can begin listening for the location and source of the leak. A stethoscope can help tremendously in tracking a leak, but an attentive ear can narrow things down in short order also.
Cracked Degas Bottle
With all of the head gasket issues associated with the 6.0L, it stands to reason that a novice would have grave worries about finding a puddle of coolant under their truck. It’s important to remember two things: 1. that chalky, crusty, while coolant residue will typically be present around the degas bottle cap from over-pressurization in the event of a blown head gasket and 2. that degas bottles are fairly prone to cracking. They’re known to split at the seams but have also been found to spring leaks due to age or exposure to heat. With a small mess and a little labor, the degas bottle can be replaced with relative ease. Just make sure you stick with an OEM replacement (cheap aftermarket versions are known to fail in as little as a few months) with a new style cap.
Wire Harness Chafing
Ford seemed to have attempted to address (or avoid) the 6.0L’s wire harness chafing issues when the engine wiring harness was redesigned on late ’03 model year engines. However, wire chafing (primarily due to vibration and a lack of anchoring) remains common—especially as the 6.0L engines continue to age. Rough idle and random stalling are typical results of chafed or exposed wires. Short-to-ground tests and moving the wire harness by hand with the engine running are common means of tracing a wiring issue, but it’s important to remember that most chafing issues occur due to friction, so always start by inspecting areas where the harness touches the engine or where it is no longer anchored in place. In particular, it pays to make sure the OEM clips intended to fasten the wire harness in position are in place any time you notice an issue or make a repair.
Thinking of buying a used 6.0L? Don’t let it become a basket case, educate yourself with this series and start with priority number 1: the oil cooler!