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How to Install a Mishimoto Racing Thermostat on Your 1996-2004 Mustang GT, Mach 1 or Cobra

Installation Time

1 hours

Tools Required
  • 10 mm socket for removing thermostat housing and alternator bracket bolts
  • 8 mm socket for removing battery terminal cable
  • Extension
  • Ratchet
  • Torque Wrench for re-installing thermostat housing bolts
  • New O-ring
  • Coolant
  • Bucket for catching coolant
  • Vice Grips
  • Screwdriver for popping out the old thermostat
  • Funnel
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1.  Step one is to empty the coolant. Depending on the size of bucket, you will need to jack the car up. Be very careful before opening the radiator drain plug as coolant is dangerous and toxic. Place your bucket under the car and slowly open the drain plug until a stream of coolant is coming out. This is a great time to flush your coolant system. Make sure to remove the coolant reservoir cap so that all of the coolant comes out.    

2. Get your 10 mm socket, an extension and your ratchet. Undo the alternator bracket bolts. Remove the bracket.    

3. Now remove the thermostat housing bolts. They are also 10 mm bolts. They are going to be pretty solid but with a good amount of force they will move.    

4. Pull off the thermostat housing and hose. You can disconnect the hose from the housing. To this you will require vice grips or pliers to pinch the metal clamp and slide the hose off. This is not necessary.    

5. Use a screwdriver to carefully pull the old thermostat out. Be careful not indent the housing. Vice grips may also work well for this step.    

6. Place new thermostat and o-ring into where the old thermostat was. If you push down on the thermostat, it will pop into place. It will not stay exactly where it was because the spring will push it back up. Make sure the o-ring is in position for a good seal.    

7. Now get your torque wrench. Set it to 18 ft/lbs or 25 Nm. Put the housing back on and tighten up the bolts.    

8. Reattach your alternator bracket.

9. Close your radiator drain plug and refill your coolant with your choice of coolant.

10. Important* When filling coolant or before remove the positive battery terminal connection to reset the ECU.    

11. When you are finished filling the coolant reattach the positive battery connection and you are ready to take the car out for a drive. Make sure that you have added enough coolant as air pockets with work their way out after a good drive.

Installation Instructions Written By AmericanMuscle Customer Michael Riola 4/1/2013