How Do I Replace the Thermostat on a 1989 Mustang?

If you are still driving around town in your 1989 Fox Body Mustang, chances are you are doing so because of that 5.0 engine Ford stuffed into the engine bay. The Fox Body era started the aftermarket explosion for the Ford Mustang franchise. Mustang owners took advantage of the solid 5.0 engine and started building huge horsepower by adding on parts like turbochargers and superchargers. But added horsepower adds additional stress on the thermostat. The thermostat has to work harder to keep the engine cool because additional horsepower causes an engine to run hotter.

Instructions

1

Trace the upper radiator hose to the location where it connects to the Mustang's intake manifold. The metal cover that the hose connects to is called the thermostat housing. The housing holds the thermostat into the intake.

2

Loosen the band clamp that holds the hose onto the thermostat intake, then slide the clamp back onto the hose. Pull the hose off and drain the contents of the hose into a clean container. Push the hose off to the side to gain access to the thermostat housing.

3

Remove the two bolts that secure the thermostat housing onto the intake manifold. Press a scraper between the intake and the housing to break the seal between the two. Over time, the gasket becomes sticky.

4

Scrape the old gasket material off the intake and the thermostat housing. Do not get any of the old gasket material into the hole in the intake.

5

Lift the old thermostat out of the intake manifold and place the new one into the manifold. One end of the thermostat has a large spring on it. Place the end with the spring into the manifold.

6

Place a bead of RTV gasket sealer around the thermostat, on the sealing base of the intake. Place the new gasket into place. Place another bead of sealer on the bottom of the thermostat housing. Place the housing on top of the gasket and secure it with the original bolts. The sealer promotes a better seal between the gasket and the metal intake and housing.

7

Secure the hose onto the thermostat gasket, then top off the radiator with a 50/50 mix of radiator fluid and distilled water.