How to Replace a 1.8T Thermostat

1. Allow the 1.8T engine to cool for several hours so that you don't risk burning yourself. Then lift up the front end, using the jack, and put the car on a pair of jack stands. Put the drain pan underneath the front of the radiator and open the petcock on the radiator. Let all of the coolant empty into the drain pan.
2. Unbolt the thermostat housing from the bottom of the engine using a 3/8-inch ratchet, extension and socket. Pull the housing off of the engine, then make a mental note of the orientation of the thermostat. Pull the thermostat out of the housing and discard it.
3. Pull the o-ring out of the housing and install the replacement. Then install the replacement thermostat in the housing in the same orientation as the original. Bolt the housing back to the engine using the 3/8-inch ratchet, extension and socket.
4. Open the radiator cap. Fill the radiator with the 50-50 prediluted coolant. Lower the car off the stands using the jack. Start the car and let it run for 15 minutes with the heater set on high. Turn off the car and let it sit for an hour. Open the radiator cap and top off the radiator with the 50-50 prediluted coolant.