Overheating
Symptoms
Temperature gauge climbs into the red zone, particularly in slow traffic or on hot days. Coolant may boil over. Persistent overheating causes head gasket failure and head warping.
Cause
The M10's cooling system was designed for German weather, not Australian summers. The original radiator loses capacity as internal passages corrode. The thermostat sticks. The water pump impeller corrodes. Electric fan switches fail. Many 2002s have had their cooling systems neglected for decades.
Fix
Upgrade the radiator to a larger-capacity aluminium unit ($300-500).
Replace the thermostat (make sure it opens at the correct temperature, 80°C).
Replace the water pump if it has any play.
Ensure the electric fan operates correctly.
Consider an additional electric fan for cars driven in traffic.
Total cooling system refresh: $400-800.
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