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John, Master Automotive Technician
Category: Car
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Experience:  ASE A1-A8 & L1 Master GM Tech 40 years experience
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How do I replace the thermostat in my 2001 Saturn SL 1.9L?

Customer Question

How do I replace the thermostat in my 2001 Saturn SL 1.9L?
Submitted: 8 years ago.
Category: Car
Expert:  John replied 8 years ago.

Hello janie g 01,

Here is some info that should help you.

Engine Coolant Thermostat Replacement

Tools Required

Universal Clamp Pliers

    Object Number: 872047  Size: SH

    Important: During extremely cold weather, -12°C (+10°F) or colder, the engine's coolant temperatue will decrease quickly when idling with the heater fan on high speed, and cool air may flow from the heater outlet.

    The fan control switch should be set at a slower speed position (fan speed I or II) to maintain the hottest air flow.



  1. Drain the coolant from the radiator and engine drain plug located at the right front of the engine.
  2. Disconnect the lower radiator hose at the thermostat housing. Object Number: 871724  Size: SH

  3. Remove the two bolts in the water inlet housing.
  4. Remove the water inlet housing and thermostat assembly.

    Important: The O-ring gasket must be replaced whenever the thermostat housing is removed.

  5. Remove the O-ring.
    Object Number: 876608  Size: SH

    Important: The thermostat element should not be removed if the assembly requires testing.

  6. Remove the thermostat element using the service tool provided with the replacement element.

    Notice: The thermostat will not function correctly once it is contacted by oil. If oil is found in the cooling system, it must be flushed and the thermostat's cartridge replaced.

  7. Inspect the thermostat components for damage, seat deterioration, etc.

    Notice: Use extreme care and do not damage or scratch the machined aluminum surfaces. Leaks will result.

  1. Check the valve opening temperature.
  2. Insert a small paper clip or tag wire between the main poppet valve seat and housing.
  3. Suspend the thermostat from the paper clip in a pan of water and gradually heat the water.
  4. Check the water temperature immediately after the thermostat falls off a tag wire or small paper clip.
  5. Replace the thermostat if it does not fall within specifications.


    New - valve opening temperature: 84-88°C (182-190°F)
    Used - valve opening temperature: 83-89°C (180-192°F)

    Object Number: 876603  Size: SH

  6. Check the full valve opening temperature.
  7. Use a pair of calipers and check the distance between the thermostat bypass valve and the frame when the thermostat is cold.
  8. Heat the thermostat in water until the main poppet valve fully opens.
  9. Measure the distance between the frame and bypass valve.
  10. Subtract the valve open reading from the close position measurement.
  11. Check the water temperatures and measurements to make sure the thermostat is opening at the proper temperatures and to the correct lift.


    New - valve opening temperature: 100°C (212°F)
    Used - valve opening temperature: 105°C (222°F)

  12. If the valve opening temperature is not within the specification, replace the thermostat.
  13. Check the valve lift.


    New - minimum valve lift: 7.5 mm (0.295 in)
    Used - minimum valve lift: 6 mm (0.236 in)

  14. If the valve full opening temperature or lift are not within the specifications, replace the thermostat.
    Object Number: 876673  Size: SH

  15. Check that the main poppet and bypass valve springs are tight when the thermostat is fully closed. If necessary, replace the thermostat assembly.
  16. Check the main poppet rubber seat. If the rubber is deteriorated, replace the thermostat cartridge.
    Object Number: 876675  Size: SH

  17. Check the thermostat for leakage around the main poppet and check the valves.
  18. Install the lower radiator hose on the thermostat housing assembly and fill the hose with clean water.
  19. Install a plug with an adapter in the other end of the hose.
  20. Place the thermostat in a two quart container and apply five 35.5 kPa (5 psi) of shop air pressure.
  21. Measure the amount of leakage from the assembly for 5 minutes.


    New - maximum leakage after 5 minutes: 0.89 L (1.68 pts.)
    Used - maximum leakage after 5 minutes: 0.95 L (2 pts.)

  22. If the leakage exceeds the specifications, replace the thermostat assembly.

Object Number: 871712  Size: SH

    Important: Make sure the element's retaining tangs are properly seated in the two legs and the element piston is correctly positioned in the water inlet housing.

  1. Replace the thermostat element using the service tool provided.
    Object Number: 871724  Size: SH