The Definitive P2 XC90 External Transmission Cooler Writeup

FOREWORD

If you have a 2007+ V8 (or 3.2) Volvo XC90 and plan on towing, one of the first things youll find is pages upon pages of forum threads talking about transmission fluid and cooling. This guide, I hope, will serve as a definitive guide for someone looking to install an OEM transmission cooler for cheap!

Please note: If your car was equipped with the Tow Package from the factory. This cooler will have already been installed.

PREREQUISITES

For this project you will need the following tools and materials:

• Impact gun OR wrench + socket set with various metric sizes.

• Various torx bits.

• Various phillips and flat blade screwdrivers.

• Trim / Bone tool (non-marring scrappers also work).

• Harbor Freight U-Clip and Screw Pack

  • Not needed if necessary u-clip is removed from donor vehicle.

• Harbor Freight Automotive Fastener Pack

• Long Reach Funnel (I used a specific one from IPD designed for reaching transmission fill holes).

• Hose Clamps

• Idemitsu TLS-LV Automatic Transmission Fluid

• 3/8ths Hose to -6 AN Male Fitting

• 3/8ths Hose to -6 AN Female Fitting

  • Optionally a 3/8ths Barb Fitting can be used, however I went with AN fittings since it makes it easier to separate the lines to do fluid changes.

• 5 or 10 Quart Measuring Buckets (Easy to find at almost any hardware store).

• OEM Volvo XC90 Transmission Cooler with lines.

  • Things to note: You can easily find these on all T6 models as they came standard from the factory with this cooler. They will have one line that runs from the top of the radiator cooler down to the unit, unclip this from the top and leave clipped in at the bottom. The return line from the external cooler to the transmission is extremely hard to unbolt, so we will cut this line as far down as possible towards the transmission.

  • I found that squeezing the clips and gently twisting the hose allowed it to pop free easily without a single broken clip anywhere along the install and test fitting process.

  • This unit can be purchased new from Volvo here, however this is expensive and also requires unbolting the lines from the transmission to install. the replacement return line from the cooler.

Guide

Throughout this guide, I may make references (and link to) other guides on Swedespeed and other various forums. This will be done to save myself time, and often these guides have better photos for the task at hand. This guide is also being written with the assumption that the end user has basic mechanical knowledge, and is familiar with their vehicle to some extent. This is NOT a hard project, and can be done using almost all basic hand tools. Additionally, if the parts mentioned have been pulled from a junkyard vehicle, much of the process is the same, just in reverse. This guide may help you in removal of the donor unit if followed in reverse order.

To start, lets begin with removing the front bumper of the vehicle. I followed this guide here. (NOTE: Do NOT follow the guides way of removing the headlights, there is a main harness connector further down from the lamps that can be disconnected to remove the headlights without unplugging the harness from the unit itself!) I used a strong non-marring plastic tool to pop the corner clips close to the fender, they were very strong! And helps to work at them slowly, releasing a tab one at a time. The two clips under the bumper were destroyed in my process (which is why I bought the cheap set of automotive clips from Harbor Freight). With the bumper off you should be left with this:

Next we will remove the lower metal skid plate to give us better access to the hoses and bolts. I used a deep socket for these as they have 3 bolts on each side, with one being up inside the front structure of the car.

With this skid plate out of the way you will have easy access to the transmission lines as well as the mounting points for the cooler. Lets begin mounting the cooler in place without the hardlines installed. You need to remove the 2 bolts that hold up the power steering fluid cooler. The external transmission cooler sandwiches between the various radiators and coolers, and uses the same bolts as the PS cooler.

Now that the cooler is mounted in place, you can disconnect the return line from the top of the radiator-integrated ATF cooler. The diagram below shows how the new lines will be run.

This diagram shows the flow of fluid as it completes its loop out of the transmission and into the coolers. Top is stock, bottom is the route with the tow package / cooler.

We can now focus on prepping our modified return line that will bring the ATF fluid from the external cooler back into the transmission. This is where the AN fittings I used come into play. I chose AN fittings due to their availability, as well as ability to hold fluids at various temp ranges and pressures. This also allows me to disconnect the lines at any point for a fluid flush without having to remove any hose clamps. I added a 3/8ths barb to -6 AN Female fitting to the cut off end of the return line that will go out of the external cooler and into the transmission.

Now we can connect the two lines to the external cooler. The inlet hose and the outlet (return) line. We are going to use the unterminated return line as a drain line for doing the ATF flush.

The two brackets on the cooler lines should line up together, and there is only one way for them to sit next to each other. This is where you will need the u-clip and screw, as it holds these two brackets to the plastic mounting point on the radiator assembly as pictured above.

While the system was apart this is the perfect time for an ATF flush. The external cooler adds extra capacity to the system, so new fluid is needed anyways. I followed this guide on Swedespeed, but instead of using a hose out of the outlet of the built in radiator cooler, I bent the outlet hose of the external cooler down into a bucket. I did 2.5 liters at a time, as a lot of fluid gets “stuck” in the torque converter when its running.

https://www.swedespeed.com/threads/how-to-xc90-6-speed-transmission-fluid-flush.204760/

Once I was happy with the level of fluid in the system, I went to the last modification step which is cutting the OEM return line to add my AN fitting. if you refer to the diagram earlier in the post you will know that we have to connect the outlet line of the external cooler to the original return line to the transmission. For this I cut the line fairly close to the metal end, and added a 3/8ths barb to -6AN Male fitting.

My hose clamp on the male end wound up over some of the hex of the fitting but it did not affect the intall.

You can use a standard wrench to connect these, or a specific AN wrench. Either way, with the two ends threaded together we now have a complete loop of the system. Make sure to put the car in reverse and drive a few times to make sure your ATF fluid level is okay. Add more if needed.

With this all done it is time to do all the steps we took in disassembling the car but in reverse. Adding the skid plate back, then the bumper and headlights. You have now installed an OEM cooler for pennies on the dollar compared to buying it new or having a shop or dealer install it for you!

As always, if there is anything you think I missed, or any recommendations please feel free to leave them in the comments or share your install process.