How to Troubleshoot a BMW Cooling System

1. Replace the coolant. By replacing the coolant at regular intervals as suggested by your BMW owners manual, you can resolve many potential issues with the cooling system. The manual will give you the exact amounts and procedures for your particular model BMW.
2. Examine the water pump drive belt. The driving belt controls the operation of the water pump. The belt may need a tension adjustment or a replacement if it has stopped working. Its a common cause of BMW cooling system issues.
3. Check the hoses of the cooling system. Look for any holes, cracks or leaks. If you find any of these issues, order replacement hoses (hoses should be changed every two years as a part of your BMW maintenance schedule). Check the other parts of the cooling system for leaks and clogs as well, including the radiator, heater valve and control valves.
4. Get a reading from the thermostat of your BMW cooling system. If the temperature gauge drops suddenly from high to low, then this could indicate that you have a sticking thermostat or a problem with your fan clutch.
5. Review the speed and efficiency of the fan of your BMW cooling system. Use the auxiliary fan switch on your BMW to check the functionality of the fan to determine if this could possibly be the issue.