|Install Guide: Zero/Sports Cool Thermo Thermostat
This method works just fine, except that the drain plug you open spills coolant allover the subframe which makes it hard to catch in a bucket, making a big mess everywhere.
4. The second method is a bit easier and cleaner. At the bottom of the radiator on the drivers side you will see where the lower radiator hose connects to the thermostat housing. To drain the coolant, remove both radiator caps (only one on some models), place the widest bucket you can find under the thermostat housing, then after removing the hose clamp, remove the hose as slowly as you can. Coolant will start to pour out pretty fast so you will want to get the end of the hose right into the bucket. Coolant inside the motor will be draining slowly out of the thermostat housing too.
5. Once all the coolant has drained out, you can remove the thermostat housing. It is held in by two 12mm bolts. One can bee seen easily in the picture, but the other is hiding behind the inlet for the housing.
6. Once the housing cover is off, you will be able to see the old thermostat. It might tale a little work to pry it out, and there might also be some more coolant hiding behind it waiting to pour out so keep that bucket handy.
7. Insert the new Zero/Sports Thermostat oriented the same way as the stock one fit inside the housing. Replace the cover/bolts and torque to 10 ft/lbs. Reattach the lower radiator hose to thermostat housing and re-tighten hose clamp.
8. Follow the instructions in the service manual page seen earlier to refill the system with coolant.
9. Enjoy your cooler running Subaru!