Section 531 (Engine Cooling System): Thermostat: Inspection

WARNING: This page is about a different car, the 2007 Lexus RX 350. However, it is still accessible from the selected car via links, so may be relevant.

INSPECT THERMOSTAT
1. Inspect the thermostat.
  HINT:
  
  The valve opening temperature is inscribed on the thermostat.
  
  Fig 1: Identifying Temperature Mark On Thermostat
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Immerse the thermostat in water and gradually heat the water.
  
  Fig 2: Immersing Thermostat In Water
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3. Check the valve opening temperature.
  Valve opening temperature:
  
  80 to 84°C (176 to 183°F)
  
  If the valve opening temperature is not as specified, replace the thermostat.
4. Check the valve lift.
  Valve lift:
  
  7.7 mm (0.3031 in.) or more at 95°C (203°F)
  
  If the valve lift is not as specified, replace the thermostat.
  
  Fig 3: Checking Valve Lift
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
5. Check that the valve is fully closed when the thermostat is at low temperatures (below 40°C (104°F)).
  If it is not fully closed, replace the thermostat.