HINT: The thermostat is numbered with the valve opening temperature.
(a) Immerse the thermostat in water and gradually heat the water.
(b) Check the valve opening temperature.
Valve opening temperature: 80 - 84C (176 - 183F)
If the valve opening temperature is not as specified, replace the thermostat.
(c) Check the valve lift.
Valve lift: 10 mm (0.39 in.) or more at 95C (203F)
If the valve lift is not as specified, replace the thermostat.
(d) Check that the valve is fully closed when the thermostat is at low temperatures (below 40C (104F)).
If not closed, replace the thermostat.