Transmission Cooler Install on a Toyota 4Runner
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By: Ziad Matloub. October, 2002.

Since I already had my bumper off to install the TJM T-15, I thought it would be a good time to install a transmission cooler.

I purchased a Hayden 679 X-HD Transmission oil cooler (11"x11") from AutoZone, part # 238922, for around $56. It came with almost all the needed hardware, I say almost because I didn't want to replace the stock hose. I wanted to connect it with the hose supplied with the cooler. The reason will become apparent in the pictures. Basically it is recessed and would have been hard to get my hand in there to disconnect/connect it.


Installation of the cooler is a cake walk. The challenge lies in getting it in the correct position. The Hayden connects in series with the 4Runner RETURN line. The Return line on the 4Runner is on the passenger side.

It is best to do the installation when the truck is cool. I didn't drive mine the day before the install.

To start off, remove the skid plate.

You will need a pair of vice pliers to clamp the hose going into the radiator. Once you pull the hose out, you will need to plug the exposed end coming out of the radiator. It may start leaking fluid. Get either a friend to plug it with a finger or some Styrofoam, etc...

Remove center bracket
Position the cooler

I found that removing the center bracket makes it much easier to get the cooler into the right position.

Then get the cooler into place, as close to the final position as you can get it. Measure the hoses taking into account the way you're going to use the coupler to connect them (below) and cut the hoses accordingly.

You need to disconnect one hose in two different spots. The Hayden will connect between these two spots.

The hose Coupler Passenger side

As you can see in the first image above, the leftmost circle marks where the hose connects to a copper pipe going back to the transmission. It seemed hard for me to get my hands in there to replace the whole hose without spilling most of the fluid so I just used the existing hose and got an in-line hose coupler to join the two hoses. Just don't forget to clamp both sides of the coupler.

Now connect this hose to the cooler and connect the other hose that goes from the Radiator (Above right image), to the other end of the cooler.

Once all hoses are clamped and ready, it is time to apply those foam stickers that came with the Hayden. In hindsight it would probably be better to stick those on before you get the cooler into place.

Foam stickers Another shot

Now Just feed the zip ties through and insert the locking plastic nut on the fan side.

Zip Ties Plastic nut

There may be other ways to route the hoses to clear the skid plate, this is the one we found to be best. The top hose should be routed as seen in the images below. The bottom hose needs to be routed through the BLUE circle as seen in the images.

Bottom hose Both hoses

Zip Ties
Don't forget to clean up those wires.

Once the hoses are in place, zip tie them together and to something sturdy. I put multiple zip ties in case one broke. When you are sure all is secure, check the ATF level, there may have been some spillage and/or leaking during the installation. You should also top off the transmission oil reservoir. Start the vehicle and check for leaks. The last thing you do is put the skid plate back on, paying extra attention that you do not pinch any of the hoses.

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