MINI R56 Thermostat Housing Replacement

So, I’ve been putting off fixing my car for a couple weeks now, and I finally got around to working on it. R56 MINI coopers have a know issue where at around 55k ~ 60k miles, you’ll get a “P0597 Cel:Thermostat Heater Control Circuit/Open” error code. This error is mostly harmless and essentially boils down to a temperature sensor not reading anymore (although, I should note that if your car’s engine overheats for some other reason, then this issue might not be harmless!!). You will also typically find that the housing attached to the sensor is leaking coolant. Below is my old assembly.

Coolant Sensor and Housing

So, now that you have this wonderful code, how do you fix it? Well, you could take it to the dealership, but after parts and labor, you’ll be looking at about $700 worth of repairs! The housing was about $125 out the door from my local dealership, which is considerably less!
In order to perform this repair, you’ll need a couple tools:

  • 10mm socket with wrench, 3″/6″ extensions (a thin-walled socket is recommended, but not necessary)
  • Pliers, channel locks, and/or a coolant hose clamp tool
  • Flashlight
  • Bucket/oil catch pan/cat litter (to pick up coolant)

You will also need the following consumables:

  • 1 x Thermostat housing
  • 1 x Gallon of antifreeze
  • Shop rags/paper towels
  • 3 hours of your time
  • Handfull of zip ties

The tools and supplies may vary depending on what needs to be removed in order to get your air intake removed.

Now, down to business!

  1. First thing you’ll want to do is let the car cool off! You don’t want to be working with coolant when the car is 150+ degres F!
  2. While the car’s cooling off, disconnect the negative terminal of the battery. VERY bad things will happen to yourself and your car if you try and start it while the coolant system is in pieces! As a general tip, be sure to roll down the windows and unlock all the doors before you do this. If there’s no power, then there are no electrical locks, right?
  3. Once the car is cooled off, go ahead and remove your air intake. I’ll leave these instructions open-ended since these can vary. Also, if you can’t figure that out, I really don’t recommend you do this repair by yourself.
  4. Remove the hose that funnels cold air to your intake. It’ll be in the way!
  5. Optional, but I recommend removing the wastegate tube (black tube that comes from the firewall to the top of the engine, traveling over the air intake hose).
  6. Next, you’ll want to remove the black plastic housing covering your ECU wires. The housing is a shell held together with a couple plastic tabs. I recommend using a knife or flat head screwdriver to bend the tabs out and gently pry it off.  Try to move the wires out of the way, cutting zip ties as necessary. It shouldn’t be too bad, although it takes a bit of patience to get it worked off. Keep in mind that those are your ECU wires. If you cut or knick one, use some liquid electrical tape or similar to seal the wire back up!
  7. Once that’s gone, you should have a clear view of the housing. Disconnect the two wires from the sensors and LABEL THE WIRES!! I can’t stress this enough! It’s very easy to swap wires around.
  8. For the rest of the writeup, I’ll use “front” to describe tube locations. Assume that “front” means “towards the direction of the front of the car”.
  9. Now the fun part! We get to play with antifreeze! Remove the large, front two coolant tubes, checking to be sure that the tubes are in good shape and are not cracking.
  10. Next, remove the two tubes towards the back of the housing. These tubes should be flexible enough for you to pull them out with a bit of force. They should also be flexible enough to be pulled out. Note that you’ll start to lose lots of coolant once you pull these two tubes.
  11. You should now be left with one tube connected on the front of the housing which leads to the turbo, and a large tube which runs behind the engine. It’s much easier to work the larger tube loose, so reach behind the engine and pull a metal clip up, away from the connection. Be careful not to drop the clip since it’ll be extremely hard to find again! Some needle nose pliers should also help.
  12. Once that’s done, remove the bolts holding the housing to the engine block. A thin-wall 10mm socket helps, but isn’t necessary.
  13. With the bolts removed, pull the housing away from the engine. The large tube should disconnect itself and you should leak fluid.
  14. As you’re removing the housing, you’ll want to loosen the only remaining clamp such that it frees itself from the last remaining tube.

Congratulations! Now you’ve removed the housing! Clean yourself off, take a break, clean the engine bay and get ready for reassembly!

  1. Reassemble everything in reverse order. Take care to slide the tube which connects to the turbo into it’s respective port on the housing.
  2. Once you’ve bolted the housing onto the engine block and connected the tubes, put the wire harness back together, using zip ties as necessary.
  3. Make sure all the sensors you disconnected are reconnected in their proper locations.
  4. Reassemble your air intake and connect the battery to the car. Do not start the engine yet!
  5. Fill your reservoir completely and let the coolant sit for a couple minutes. Some of it will work its way back into the system.
  6. On top of the housing, next to the temperature sensor, there’s what looks like a plastic nut. Turn it counter-clockwise 3 or 4 turns then let the coolant sit another 5 minutes. This port allows air to escape the housing, allowing coolant to flow into the engine.
  7. Once you don’t notice a change in coolant levels, close the air escape on the housing and start your engine. Turn on your heater and allow your car to heat up. Closely monitor coolant levels and fill as necessary. Be sure to turn off the engine before filling the reservoir and always close it when done filling!
  8. Once levels do not change and the car has been idling for 20 ~ 30 minutes, drive the car around the block a few times and check coolant levels again. If they haven’t changed, then you’re finished! Monitor coolant levels for the next few days and look for any puddles forming under the car. Small puddles are normal and should go away after a few days since a great deal of coolant is spilled during this repair.
  9. Enjoy your $600 in savings!