Replace the thermostat if it is open at room temperature. To test a closed thermostat:
1. Hang thermostat A in a container of water. Do not let thermometer B touch the bottom of the container.
2. Heat the water and check the temperature with a thermometer. Check the temperature at which the thermostat starts to open and at which it fully opens.
3. Measure the thermostat valve lift in the fully open position. Standard thermostat:
- Lift height: more than 8.0 mm.
- Beginning of opening: 80-84°C.
- Full opening: 95°C.