Thermostat
Thermostat
Section titled “Thermostat”The thermostat regulates engine temperature by controlling coolant flow to the radiator. It opens at 97°C (207°F).
Failure Modes
Section titled “Failure Modes”- Stuck open: Engine runs cold, poor heater, P0128 code
- Stuck closed: Engine overheats rapidly — stop immediately!
Replacement
Section titled “Replacement”Part: 11 53 7 509 227 (Wahler OE, 97°C). Housing bolts: 10 Nm.
Replace with every cooling system overhaul.