DIY BMW 540I Thermostat


1. Slide the drain pan under the radiator petcock. Open the petcock and allow 2 pints of coolant to drain. Ensure that the drain pan is clean, so that you can reuse the coolant.
2. Loosen the hose clamp at the thermostat, using a screwdriver. Pull the hose off the thermostat. Unbolt the three retaining bolts on for the thermostat housing, using the appropriate socket. Remove the housing. Pull the thermostat out of the housing, or engine, if it doesn't stick to the housing.
3. Clean the gasket mounting surfaces, using the rubber scraper and rags. Install the O-ring on the thermostat housing. Insert the thermostat onto the engine, ensuring that the support bar on the thermostat is facing out.
4. Install the thermostat housing and tighten the bolts to 6 lb.-feet of torque. Refill the cooling system.