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Jerry, Master Mechanic
Category: Dodge
Satisfied Customers: 17218
Experience:  ASE Master tech, 30 years exp. troubleshooter, driveability tech
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How to install a replacement thermostat in a 1999 Dodge Durango

Customer Question

How to install a replacement thermostat in a 1999 Dodge Durango, how much time would it take for a novice (experienced in changeing oil & filter,)
What to look out for etc etc
Submitted: 8 years ago.
Category: Dodge
Expert:  Jerry replied 8 years ago.

Hello and welcome to Just, Super mechanic here. About your vehicle.


It should take you about an hour. You will want to make sure that you get all of the old gaskets of before installing the new one. Here are the steps for it, thanks





Do not waste reusable coolant. If solution is clean, drain coolant into a clean container for reuse.

If thermostat is being replaced, be sure that replacement is specified thermostat for vehicle model and engine type.

Factory installed thermostat housings on 3.9L/ 5.2L/5.9L engines are installed on a gasket with an anti-stick coating. This will aid in gasket removal and clean-up.

  1. Disconnect negative battery cable at battery.
  2. Drain cooling system until coolant level is below thermostat.





  • Air Conditioned vehicles: Remove support bracket (generator mounting bracket-to-intake manifold) located near rear of generator.
  • On air conditioning equipped vehicles, the generator must be partially removed.






    1. Remove generator drive belt as follows: Drive belts on both 3.9L and 5.2L/5.9L engines are equipped with a spring loaded automatic belt tensioner.
    2. Attach a socket/wrench to pulley mounting bolt of automatic tensioner.
    3. Rotate tensioner assembly clockwise (as viewed from front) until tension has been relieved from belt.
    4. Remove belt from vehicle.
    5. Remove two generator mounting bolts. Do not remove any wiring at generator. If equipped with 4WD, unplug 4WD indicator lamp wiring harness (located near rear of generator).
    6. Remove generator. Position generator to gain access for thermostat gasket removal. WARNING: CONSTANT TENSION HOSE CLAMPS ARE USED ON MOST COOLING SYSTEM HOSES. WHEN REMOVING OR INSTALLING, USE ONLY TOOLS DESIGNED FOR SERVICING THIS TYPE OF CLAMP, SUCH AS SPECIAL CLAMP TOOL (NUMBER 6094). SNAP-ON CLAMP TOOL (NUMBER HPC-20) MAY BE USED FOR LARGER CLAMPS. ALWAYS WEAR SAFETY GLASSES WHEN SERVICING CONSTANT TENSION CLAMPS. CAUTION: A number or letter is stamped into the tongue of constant tension clamps. If replacement is necessary, use only an original equipment clamp with matching number or letter.
      1. Remove upper radiator hose clamp and upper radiator hose at thermostat housing.
      2. Position wiring harness (behind thermostat housing) to gain access to thermostat housing.






      1. Remove thermostat housing mounting bolts, thermostat housing, gasket and thermostat. Discard old gasket.


    1. Clean mating areas of intake manifold and thermostat housing.
    2. Install thermostat (spring side down) into recessed machined groove on intake manifold.
    3. Install gasket on intake manifold and over thermostat.





  • Position thermostat housing to intake manifold. Note the word FRONT stamped on housing. For adequate clearance, this must be placed towards front of vehicle. The housing is slightly angled forward after installation to intake manifold.
  • Install two housing-to-intake manifold bolts. Tighten bolts to 23 Nm (200 inch lbs.) torque.
  • Install upper radiator hose to thermostat housing.
  • Air Conditioned vehicles:






    CAUTION: When installing the serpentine accessory drive belt, the belt must be routed correctly. If not, engine may overheat due to water pump rotating in wrong direction. For correct 3.9/5.2L engine belt routing. The correct belt with correct length must be used.

    1. Install generator. Tighten bolts to 41 Nm (30 ft. lbs.).
    2. Install support bracket (generator mounting bracket-to-intake manifold). Tighten bolts to 54 Nm (40 ft. lbs.) torque.
    3. Position drive belt over all pulleys except idler pulley (located between generator and A/C compressor).
    4. Attach a socket/wrench to pulley mounting bolt of automatic tensioner.
    5. Rotate socket/wrench clockwise. Place belt over idler pulley. Let tensioner rotate back into place. Remove wrench. Be sure belt is properly seated on all pulleys.
      1. Fill cooling system.
      2. Connect battery negative cable.
      3. Start and warm the engine. Check for leaks.
    Customer: replied 8 years ago.
    IS it a good idea to replace the belt and hoses while I am in this ?
    Expert:  Jerry replied 8 years ago.
    You will want to have a look to see how they look, yes. If there are alot of cracks in the belt or if the hose(s) might feel kind of soft, then yes, you would want to replace them as well.
    Jerry and other Dodge Specialists are ready to help you
    Customer: replied 8 years ago.
    Sounds like a plan,,,I appreciate your help.
    Expert:  Jerry replied 8 years ago.

    Your welcome and come again whenever you need, thanks