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Andrew J.
Andrew J., Auto Service Technician
Category: Car
Satisfied Customers: 3
Experience:  15+ years of automotive servicing, restoration of classic automobiles, autobody repair
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Replacing Thermostat

Customer Question

how to replace the thermostat on a 1997 dodge ram van 1500
V6 3.9
Submitted: 11 years ago.
Category: Car
Expert:  Andrew J. replied 11 years ago.



Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. Disconnect the negative battery cable.
  2. Drain and recycle the engine coolant.
  3. If equipped with air conditioning:

    1. Remove the engine cover.
    2. Remove the drive belt.
    3. Remove the alternator.

      Fig. 1: The thermostat housing is located at the front of the intake manifold, and is attached by two retaining bolts

  4. Remove the upper radiator hose.
  5. Remove the upper radiator hose from the thermostat housing.
  6. Remove the retaining bolts from the thermostat housing.
  7. Remove the thermostat housing, thermostat, and gasket from the intake manifold.

    Fig. 2: The gasket usually sits atop the thermostat, as in this case. However, on some engines, the gasket is underneath the thermostat flange

    Fig. 3: Remove the thermostat from the manifold by lifting it straight up

    To install:

  8. Clean the gasket mating surfaces.

    Fig. 4: Take care when cleaning the surfaces for the new gasket; it is necessary to remove any residue to allow the gasket to adhere

    NOTE: If a new thermostat is being installed, make sure the replacement is the specified part for the vehicle.

  9. If the gasket goes beneath the thermostat flange, be sure to first install a new gasket. Install the thermostat spring side down into the intake manifold.
  10. If the gasket goes on top of the thermostat flange, install a new thermostat gasket above the thermostat.

    Fig. 5: Place the new thermostat and gasket on the intake manifold before attaching the thermostat housing

    Fig. 6: The word FRONT is usually stamped on the thermostat housing. This goes toward the front of the vehicle for installation

    NOTE: The thermostat housing may have the word FRONT on it; this goes towards the front of the vehicle.

    Fig. 7: This exploded view shows the typical order of installation of the thermostat

  11. Install the thermostat housing onto the intake manifold.
  12. Tighten the housing bolts to 200 inch lbs. (23 Nm).
  13. Reinstall the upper radiator hose onto the housing.
  14. If the vehicle has air conditioning:

    1. Reinstall the alternator.
    2. Reinstall the drive belt.
    3. Reinstall the engine cover.

      NOTE: Ensure that you have retightened the radiator drain before refilling with coolant.

  15. Refill the radiator with a proper coolant mixture.
  16. Connect the negative battery cable.
  17. Start the engine and bleed the cooling system.
  18. Ensure that the thermostat is operational (by checking the upper radiator hose for warmth), and that there are no leaks.



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