OEM 2003 Toyota Prius Thermostat

2003 Toyota Prius Thermostat Parts Q&A

• Q: How to service and repair the thermostat on 2003 Toyota Prius?

  A: The service process for the thermostat begins with draining engine coolant before continuing. Begin by disconnecting the wire harness clamp from the water inlet before taking off the 2 nuts which detach the water inlet from the cylinder block and finally removing the thermostat together with its gasket. Luxury and precision serve as criteria for testing the thermostat after hydrating it in water as you heat it up to measure its valve-opening capability - it needs to be between 80 - 84 degrees Celsius (176 - 183 degrees Fahrenheit); if this specification fails then replace the component. Examine the valve lift of the thermostat because it needs replacement if it does not extend past 8.5 mm (0.345 inch) at 93 degrees Celsius (199 degrees Fahrenheit). The valve needs to be checked for its ability to close completely when temperatures drop below 40 degrees Celsius (104 degrees Fahrenheit). Any exceptions indicate the need for thermostat replacement. The install procedure requires you to position the thermostat inside the cylinder block using a new gasket while placing the jiggle valve in an upward direction with a 10 degrees tolerance. The water inlet needs two nuts before installation while the wire harness needs to be reconnected to the water inlet and tightened to 9.0 Nm (90 kgf-cm, 80 inch lbs.). Complete the engine system by adding coolant and then start the engine while inspecting for any coolant leakage.