How To Replace Thermostat Housing 02-05 Mercury Mountaineer 4.6L

Difficulty: Intermediate · About 40 min · Mercury Mountaineer

Replace the thermostat housing on a 2002-2005 Mercury Mountaineer with the 4.6L engine.

Steps

1. Remove the engine cover

   Disconnect the negative battery cable with an 8mm wrench, remove the cover's two 11mm nuts, lift it off, then unclip the hose from its back.

2. Remove the old thermostat housing

   Squeeze the radiator hose clamp's teeth and slide it back, twist the hose off, remove the housing's two 10mm bolts, remove the alternator's 10mm nut and move its wire aside, tap the housing to loosen it, lift it off, pry out the thermostat O-ring with a flat blade screwdriver, then vacuum the area and scrub it with a wire brush.

3. Install the new thermostat housing

   Press the new O-ring into place, insert the housing, tighten its two 10mm bolts and torque them to about 19 ft-lb, reposition the alternator wire and fasten its 10mm nut, push the radiator hose into the housing, then tighten its clamp with pliers.

4. Reinstall the engine cover

   Set it into place, tighten its two 11mm bolts, clip the hose onto its back, then reconnect the negative battery cable.

5. Refill the coolant

   Twist off the coolant bottle cap, fill to the cold line, run the engine briefly, then check and top off the level as needed.

Check your vehicle’s repair manual for exact specifications and fit.