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Oil Cooler Overhaul: Rebuilding The Heart Of The 6.0L Power Stroke

Posted in How To: Engine on January 13, 2017
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Most internal combustion engines rely on motor oil for one reason: lubrication. The oil gets pressurized between 10-70 psi and spends most of its life subjected to roughly 200 degrees’ worth of heat. But then there are diesel powerplants with hydraulically activated injection systems like the 6.0L Power Stroke. Not only do these mills utilize motor oil for lubrication purposes, but the oil is also highly pressurized in order to fire the fuel injectors. Arguably no other engine oil in the world is subjected to what the 6.0L Power Stroke throws at it during its hours of operation: as much as 3,600 psi.

As you can imagine, oil that sees pressure nearing 4,000 psi gets pretty hot, and at peak demand, the 6.0L Power Stroke requires more than 18 gallons of oil per minute. This is why the oil cooler must always be in good working order. Unfortunately, several design flaws make this vital component highly unreliable in the 6.0L’s case. Its tight coolant passageways become clogged from debris present in the coolant system (casting sand or suspended solids from coolant). Over time, this deprives the oil cooler of proper coolant flow, which in turn leads to less cooling of the engine oil. Eventually, coolant can no longer make its way through the appropriate channels within the oil cooler and the oil becomes superheated. This hampers the operability of the fuel injectors, not to mention that sending 260-degree motor oil through the turbocharger, high-pressure oil pump, and the engine’s rotating assembly doesn’t bode well for the longevity of these parts either.

Ford’s oil cooler rebuild kit comes with everything you need to overhaul the oil cooler in your 6.0L Power Stroke (PN 3C3Z-6A642-CA). All gaskets, O-rings, and seals are included, as well as a new pump inlet strainer and heat exchanger. When Flynn’s Shop tackled the job for us, a complete flushing of the coolant system was performed using Ford VC-9, along with switching to an Extended Life Coolant (ELC) and installing a coolant filtration system to preserve the life of the new oil cooler.

To add insult to injury, once coolant stops flowing through the oil cooler altogether, the EGR cooler no longer receives the coolant it needs in order to remain functional and begins to overheat. Oftentimes, the welds in the EGR cooler rupture, the EGR cooler is replaced without an in-depth diagnosis, and the failing oil cooler goes unaddressed, leading to the same catastrophe recurring a short while later. Did you know that 9 times out of 10, the 6.0L’s “infamous” EGR cooler fails due to a plugged oil cooler? Armed with this knowledge, the folks at Flynn’s Shop in Alexander, Illinois, always dig a little deeper when a 6.0L Power Stroke comes in for an EGR cooler failure. Follow along to learn the warning signs of a bad oil cooler, how they’re rebuilt, and the most affordable way to ensure an overhauled unit lives a long, healthy life going forward.

Diagnosing a failing oil cooler starts with monitoring the delta (variance) between engine coolant temperature and engine oil temperature. With the engine up to operating temp, both parameters should stay within 15 degrees of each other. Generally speaking, a 3 to 6-degree delta is considered normal, while a difference of 10 degrees or more warrants monitoring. Here you can see that oil temp is a toasty 41 degrees warmer than coolant temp, which is indicative of a plugged oil cooler. It’s important to note that you cannot rely on your dummy gauges to catch a temperature discrepancy. Aftermarket gauges and monitors from Edge Products, Scan Gauge, or SCT are commonly used, as is the OEM-supported Ford IDS.
Gaining access to the oil cooler is a time consuming process due to the 6.0L Power Stroke’s compact design (where a lot of key engine components are packaged tightly together in the lifter valley). As you can see here, the turbocharger and all of its respective intercooler piping, fuel filter housing and lines, intake manifold (shown), EGR valve, and the oil filter housing all have to be removed.
After removing the M8 bolts that secure the oil cooler to the block, Chad Flynn of Flynn’s Shop pulled the oil cooler from the valley. He then proceeded to vacuum out the leftover oil from the oil cooler reservoir, followed by a thorough cleaning of the oil cooler’s mating surface on the block.
This fine-mesh screen filter (referred to as a pump inlet strainer) is the last method of filtration the oil sees before leaving the oil cooler and making its way into the high-pressure oil pump. Unfortunately, this screen is notorious for tearing and allowing debris to pass through. Luckily, a new pump inlet strainer is supplied with each OE oil cooler rebuild kit.
Once the oil cooler had been allowed to drain for some time, Flynn started the disassembly process by unbolting the EGR coolant supply cover (its two M6 bolts were retained, and torqued to 85 in-lb during reassembly). While the EGR coolant supply cover is reused, its internal seal would be replaced.
Next, the oil filter mount was separated from the oil cooler cover and its respective gasket was removed. We need to note that the installation of all replacement gaskets, O-rings, and seals supplied in Ford’s oil cooler kit is pretty self-explanatory (i.e. there are no surprises in this job, or special tools required).
In order to remove the heat exchanger portion of the oil cooler from the oil cooler cover, the entire assembly was positioned on two blocks of wood, with the exchanger hanging between them. After the exchanger’s two M8 x 20 mounting bolts were removed, a 21mm socket and hammer were used to tap the heat exchanger out of the cover, and the exchanger was scrapped (the oil cooler cover would be reused). Then the recessed inlet and outlet port O-rings were removed (via pick) from the oil cooler cover and thrown away as well.
This is the primary culprit in 6.0L oil cooler failures: the stacked-plate heat exchanger (also referred to as the oil cooler module). Some folks cut them open upon removal, which reveals a multitude of narrow coolant passageways—all chock full of debris. The debris discovered is typically casting sand from the block, suspended solid (gel-like) deposits left behind from running broken down or non-compatible coolant through the engine, or a combination of all of the above. Combustion gases slipping past the head gaskets and allowing carbon particles into the coolant passages is also believed to play a role in the coolant flow blockage that occurs.
Once every gasket, seal, and O-ring had been removed from the oil cooler cover, oil filter mount, and EGR coolant supply cover, Flynn began the process of installing their supplied replacements. Here, fresh O-rings are being fitted to the oil cooler ports on the new heat exchanger.
Prior to installing three new O-rings in the underside of the oil cooler cover (shown), Flynn inspected the cover’s sealing surfaces and threads for damage. The O-ring seal bores were also inspected for any damage that might’ve occurred during the heat exchanger’s removal and then the oil cooler cover was treated to a thorough cleaning.
Next, Flynn took care that both the vent hole underneath the oil cooler cover and the oil drain hole on the outside of the cover were clear of any debris. The paper clip shown here indicates the oil drain hole’s location.
After the O-rings on the heat exchanger’s inlet and outlet ports were treated to a light coating of motor oil, Flynn aligned the heat exchanger with its respective ports in the oil cooler cover and hand-pressed it onto the cover until fully seated. Then the heat exchanger mounting bolts were reinstalled and torqued to 16 ft-lb.
Fitted with a fresh gasket, the oil filter mount was reattached to the top of the oil cooler cover. At this time, Flynn warned us that these fasteners should never be overtightened, as the oil cooler cover features self-tapping threads. The oil filter base mounting bolts would receive the recommended 17 ft-lb torque specification.
As far as the oil cooler assembly process was concerned, the last item of business entailed finagling the new reservoir gasket into the grooved perimeter of the oil cooler cover. This gasket’s ability to stand up to extreme heat is vital, hence the reason to always opt for high-quality, genuine OEM replacement parts when performing a job as extensive as this. Some gaskets and O-rings supplied in aftermarket kits have been known to deteriorate, forcing debris toward the high-pressure oil pump or allowing oil to mix with coolant.
With the new pump inlet strainer set in place in the block, Flynn topped off the oil cooler reservoir with fresh 5W-40 Shell Rotella. It pays to top off the engine oil here in order to ease the initial engine start up process later on.
Once the oil cooler was bolted back onto the block via M8 bolts (torqued to the recommended 16 ft-lb spec), Flynn got busy reinstalling everything removed during the teardown process. We’ll note that during any oil cooler rebuild it’s an opportune time to inspect the EGR cooler and injection pressure regulator (IPR valve), clean the intake manifold, disassemble and clean the turbocharger, and even clean the EGR valve.
According to industry experts, the oil cooler on a 6.0L lasts about 50,000 miles before failure rapidly approaches. We know: that’s not a very long time—especially for trucks that are used every day for work. One of the most affordable ways to make your factory oil cooler last is to install a coolant filtration system such as this one from Sinister Diesel (PN SD-COOLFIL-6.0-W). A bypass-style system, its coolant filtration kit filters a small portion of engine coolant at a time, and all suspended solids or chunks of debris are trapped in the filter. By eliminating the possibility of debris from lodging in the oil cooler’s coolant passageways (and changing the filter at the proper interval), the oil cooler could potentially last the life of the vehicle.


Flynn's Shop
Alexander, IL
Xtreme Diesel Performance
Wall Township, NJ 07727
Sinister Diesel

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