Hey all -

I need to replace the thermostat in my truck - 2002 F150, 5.4L, FX4, about 120K miles. Now, I've done everything up to and including removing the power steering reservoir mounting bolt and the two thermostat housing mounting bolts.

Now, the book says that the housing should just "lift off". However, the thermostat housing is firmly stuck to the mounting surface and won't budge. I've tried tapping it with a hammer and block of wood, prying it up by tapping a putty knife under the edge, pulling, yanking, and cursing at it, and it won't move.

Has anyone come across this problem before? I don't want to beat on it too much because I don't want to damage it, and I can't heat it because there's too much in proximity to the housing.

Any ideas? Thanks all!

**Sorry, I meant "stuck" thermostat housing in the subject.

 

The housing doesn't just sit on the manifold, it sets IN it too. Below the mounting surface, the housing extends down into the hole, and seals against the gasket and then the thermostat. This might not be the "right" thing to do, but I'd spray a little penetrating oil around it and let it set, and then tap it with a dead blow or rubber hammer.

When you get it off, the gasket (at least on mine) sits on top of the thermostat, and may be stuck to the housing, so make sure not to forget to remove the old gasket......

 

All done - thanks for the advice, redwood. What ended up working was taking a drift pin and tapping on the bolt "ears" left and right several times each, to rotate the housing back and forth. Along with some Liquid Wrench, it eventually loosened up and came out - looks like it was just built-up corrosion that had locked it in place.

Thanks again!