Ford Enthusiast

[JohnnyQ]

Squeeze top radiator hose (when motor is cool) and watch for bubbles around the thermostat housing. The housing is injection molded plastic attached to the cylinder head (Rt. side) and prone to breakdown overtime. Small gasket inside the housing drys and cracks. Coolant leak very slowly past the gasket usually at higher idle only (while driving) Usually very slow if any at first then more and more leaking. Noticed sometimes no leak at all while at idle. Also, the small leak at the housing will not allow pressure on the thermostat, this is usually how the overheating occurs ( no coolant movement) HOT coolant doesn't pass the thermostat (high temp sensor on other side of thermostat) so fan never comes on. I replaced my thermostat and was temporary fix then noticed the housing issue. Dealer item and removed blower box and battery to get to it. Actually pretty easy. Hope it's just the thermostat. Good luck.