Bullet Proof Diesel’s New 6.4L Oil Cooler

A Simple and Economic Solution for Rising Oil Temps

Diesels are built to work hard. Typically, hard work raises operating temperatures. More fuel raises EGTs, and heavy towing not only gets the transmission hot, it can also raise both the coolant and oil temps. Most diesels are designed to handle these situations, but since adequate fluid cooling is one of the keys to longevity, increasing that cooling capacity is never a bad idea.


Bullet Proof Diesel Truck

It’s hard to believe that any truck with seven coolers out front could have a heating issue, but Ford’s 6.4L Power Stroke is prone to oil cooler failures—just like the 6.0L that came before it.


Most diesels run separate oil and transmission coolers—which are usually externally mounted—to keep temps within the normal range. Ford, on the other hand, uses a water-to-oil intercooler on both the 6.0 and 6.4L Power Strokes. This unit’s design flaw is legendary on the 6.0L, because it often leads to more expensive repairs (such as replacing both the oil cooler and EGR cooler) or worse, if coolant and oil become mixed.


Bullet Proof  Truck Parts

1) Bullet Proof Diesel’s 6.4L Half Kit comes complete with mounting brackets, a Fluidyne oil cooler, remote oil filter setup and high-pressure oil lines for an easy install by the average mechanic. What simplifies the install is a very detailed set of instructions.

oil filter

The 6.4L Half Kit taps into the factory oil system via the oil filter canister and manifold, which is the second round cap to the left.

oil filter

The install starts by removing the cap and oil filter, along with the factory canister.

In a nutshell, Ford’s oil cooler design is a square unit that rides in the valley of engine and has small passages for both the oil and coolant inside. The passages are small enough to become plugged with coolant deposits over time, and that’s when the trouble starts.

The standard diagnostic test for cooler operation is to compare the engine’s coolant temperature against the oil temperature. By factory specs, anything under 14 degrees difference, and the cooler is doing its job. Anything over 15 degrees difference, and you’ve got the start of issues with the factory oil cooler.


Bullet Proof Diesel Truck

With the oil filter assembly removed, remove the three torx-head screws that hold down the stock bypass and anti-drain back valve in the bottom.

Bullet Proof Diesel Truck

This is what the assembly will look like. The kit provides a new spring. Also inspect the rubber seal on the bypass valve before reinstalling the assembly.

Bullet Proof Diesel Truck

6) According to the instructions, you have to install two fittings on the top of the billet half-kit adapter prior to installing it where the old oil filter housing used to sit. It only goes on one way and utilizes two different-length mounting screws. The instructions tell you which ones go where.

top of the engine

This is what the installed assembly looks like on top of the engine.

If you own a 6.4L Power Stroke, the fix is not simple or cheap. Due to the tight constraints of the engine compartment, you almost always have to pull the cab to get all the stuff off the top of the engine to even access the factory oil cooler. On a 6.0L, things are not quite so tight under the hood. You have a few options at this point: Replace the stock cooler and pray it won’t crap out again before you sell the truck, or swap out the factory cooler with a full external unit, complete with remote-mount oil filter.


fuel cooler

Next, you need to remove the bumper and detach the fuel cooler from the intercooler before removing the intercooler.

flexible rubber line

The stock transmission cooler line will be removed and replaced with a flexible rubber line.

flexible rubber line

trans cooler

Carefully remove the factory line and install the enclosed fitting into the trans cooler.

Bullet Proof Diesel Truck

Bullet Proof Diesel Truck

The kit comes with a push lock hose connector that connects a #8 AN fitting, which is added to the trans cooler.

But Bullet Proof Diesel, in Mesa, Arizona, has developed a new fix for the 6.4L that doesn’t require cab removal and retains the factory oil cooler to get the oil up to temp quicker in colder climates. Bullet Proof Diesel’s 6.4L Half Kit, as the company calls it, is a great compromise between Bullet Proof’s full oil cooler replacement system, which does away with the factory cooler entirely, and the stock fix.


Bullet Proof Diesel Truck

To make access easier to run the cooler lines and install the remote oil cooler assembly, the factory headlight and inner fender are removed.

Bullet Proof Diesel Truck

The heart of the remote oil filter system is this billet manifold. It’s easier to install the fittings before you mount it on the truck.

Bullet Proof Diesel TruckBullet Proof Diesel Truck

Bullet Proof Diesel Truck

The manifold is then bolted to the mounting bracket, and the spin-on filter is also added before the assembly is mounted in the fender well of the truck.


The kit incorporates an external Fluidyne oil cooler that works in conjunction with the factory unit to drop temps when they start to get outside the normal range. It’s also a simple add-on insurance package for folks who tow with their trucks. The system plumbs into the stock oil cooler via the factory oil filter canister and relocates the oil filter to a much larger, fender-mounted unit with a simple screw-on, commercial-grade oil filter. According to Bullet Proof, a typical installation will add 3 to 4 more quarts of oil to the engine and drop oil temps on the average of 15 degrees, depending on the condition of the stock oil cooler.

Bullet Proof Diesel Truck

Bullet Proof Diesel Truck

Next up, the oil cooler is attached to the mounting bracket, along with a loop, to secure one of the cooler lines.

Bullet Proof Diesel Truck

Bullet Proof Diesel Truck

The mounting bracket is designed to fit into an existing slot on the intercooler. The other end is secured with self-tapping screws.

Removing excess heat from the engine also reduces the strain on the cooling system in general. And even though the 6.4L Ford utilizes no less than seven radiator/coolers, there’s still room for one more without transferring too much heat behind it. According to Bullet Proof, the Half Kit also buys you more time before you eventually have to replace the factory oil cooler.

Bullet Proof Diesel Truck

Bullet Proof Diesel Truck

Now, it’s time to hook up the oil lines. The instructions tell you which line gets hooked up where so there is no confusion. The billet adapter on top of the engine makes routing the lines easy.

Bullet Proof Diesel Truck

The newly installed trans cooler line is secured next and attached to the factory line.

More importantly, Bullet Proof says the average driveway mechanic can install the kit in a few hours with hand tools. The install is made even easier with some of the most detailed instructions we’ve ever seen for an aftermarket product. Plus, Bullet Proof has tech support available if you get stuck.


Bullet Proof Diesel Truck

With all the lines in place, it’s time to fit the intercooler back into the truck, complete with the new oil cooler attached. The cool, red step you see here is Bullet Proof Diesel’s tech step. It attaches to the factory tow hooks that make working on the truck that much easier.

Bullet Proof Diesel Truck

With the assembly mounted, it time to hook up the boost tubes and all the oil lines.

Bullet Proof Diesel Truck

Here’s what the finished oil cooler install looks like … very clean

Bullet Proof Diesel Truck

You can see that in relation to all the other coolers on the 6.4L, the Bullet Proof Diesel setup looks factory. All that’s left is to put the bumper back on and re-install the headlight and inner fender.

Bullet Proof Diesel’s new Half Kit for the 6.4L is not only a good solution to the factory oil cooler issue, it also buys you some peace of mind with added cooling capacity when towing heavy.

Bullet Proof Diesel Truck

This is now what you see when you open the hood.



Bullet Proof Diesel

4245 E. Palm Street

Mesa, AZ 85215



Fax: 480.268.7564



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By Kevin Wilson

Photography: Kevin Wilson


Posted in Tech Tagged with: , ,
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  1. Steve white says:

    Right now I’m seeing temps from : 194ect, 215eot and have seen EOT’s as high as 221
    Do you think your kit will help me, or should I change oil cooler ? Looking for the easy way out…lol
    Do you guys sell a full kit for the 6.4 which gets rid of stock cooler all together? Any info would be appreciated, thanks, Steve white, Canada