2001 Ford Ranger 4.0L SOHC 150k miles Replacing the thermostat housing as it's leaking profusely. The "center" bolt will not budge. The two on the "outer" came out relatively easily. I've sprayed with penetrating oil multiple times & have let it soak for hours. I'm not very experienced with getting out bolts that are this stubborn. We don't have salt here! Since heating it would destroy the housing but it's garbage anyway so don't see where that would hurt. Heating the top would seem to be a waste so would have to heat near the bottom where the threads are located. The head is getting rounded now so not much more to try. I'm trying to replace w/o removing the intake manifold & perhaps that's hindering me more than it should. I had assumed that I could remove the other "sensor" as I'm pulling out the housing. Perhaps not though. Thank you.