How to Install a Thermostat in a BMW

1. Place a drain pan underneath the radiator drain plug of your BMW and then take the cap off of the radiator. Turn the radiator drain plug with a pair of pliers and allow the coolant to drain out completely. Once the radiator is completely drained, turn the drain plug and shut off the coolant drain. Use an old coolant container and pour the discarded coolant into the container. Use a marker to label the old container as 'used' coolant.
2. Find the engine coolant plug at the back of the BMW engine, near the oil drain plug. Place the drain pan under this plug and use a metric socket wrench to undo the plug and allow the coolant to drain out of the motor. When the coolant has completely drained, tighten the drain plug and remove the drain pan. Pour the discarded coolant into your used coolant container.
3. Identify the alternator cooling duct, located at the front of the engine running from the alternator to the radiator. This tube will slide off without any fasteners or clips. Remove the tube and set it off to the side. Locate the six screws that were under the tube, holding a shroud in place.
4. Undo the six screws holding the shroud with a metric socket wrench. Locate the two hose clamps that are attached to the thermostat housing and loosen them using a screwdriver. Remove the hoses and locate the cooling fan under the hoses, and remove the bolts to the fan with a metric socket wrench. Hold the fan while you are removing the bolts to keep it from falling. When the bolts are loose, set the cooling fan aside.
5. Unfasten the bolts that are holding the thermostat housing in place with a metric socket wrench and remove the housing. Examine the thermostat and take note of the position of the arrow on the thermostat. Take the thermostat out of the housing and use a piece of emery cloth to clean the area around the face of the housing to clean off any remaining gasket material or debris.
6. Place a bead of gasket seal around the face of the thermostat housing and position the new thermostat in the housing with the arrow pointed in the same direction as the one you removed. Attach the thermostat housing with bolts and reattach the cooling fan. Place the hoses back over the thermostat housing and tighten the clamps with a screwdriver.
7. Position the shroud cover over the cooling fan and secure with screws and a socket wrench. Slide the alternator cooling duct tube back into place and refill the radiator with coolant. Once the radiator is full, put the cap back on the radiator and start the BMW motor. Let the motor warm up for about five minutes to verify that the thermostat is working properly and then turn off the engine.
8. Discard the used coolant by taking it to the local recycling center or automotive recycling center.