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 to 84€D (176 to IBS®1)

If the valve opening temperature is not as specified, replace the thermostat.

(c) Check the valve lift.

Valve lift: 10 mm (0.394 in.) or more at 95#D (203W)

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 77€C (171^)).

If not closed, replace the thermostat.


If the reservoir cap has contaminations, always rinse it with water.

Before using a radiator cap tester, wet the relief valve and pressure valve with engine coolant or water. When performing steps (a) and (b) below, keep the tester at an angle of over 309above the horizontal.

Radiator Cap Tester

(a) Using a radiator cap tester, slowly pump the tester and check that air is being released from the vacuum valve. Pump speed: 1 push every 3 seconds or more


Push the pump at a constant speed.

If air is not being released from the vacuum valve, replace the reservoir cap.

(b) Pump the tester and measure the relief valve opening pressure.

Pump speed: 1 push within 1 second NOTICE:

The pump speed above should be followed for the first pump only. It will close the vacuum valve. Once the vacuum valve is closed, the pump speed can be reduced. Standard opening pressure:

78 to 122 kPa (0.80 to 1.25 kgf/cm2, 11.3 to 17.8 psi)


Use the tester's maximum reading as the opening pressure. If the maximum reading is less than the minimum opening pressure above, replace the radiator cap.

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