Suspect water pump

Dreadnaught

Just because there aren't any bubbles in the coolant doesn't mean you have a head gasket issue. You need to get a block tester so you can better diagnose if you have a head gasket issue. I just had a car a few weeks ago that had blown head gaskets and when we took the car for a road test and monitored the Engine Coolant Temperature, the temp would barely get above 210. Once, we got back to the shop and took the cap off the degas bottle there was an extreme amount of pressure in the cooling system.

Are you sure that your fans aren't intermittently not working?

I don't think its your water pump, our water pumps have metal fins pushing coolant through the engine. But hey, don't rule out broken water pump fins even though I've never seen someone said that they had it happen to them. Here at Ford, like on the 3.5, the fins are plastic and will come apart sometimes at about 100K then the car will over heat. Another way too check if it could be your water pump is witness marks coming from the weep hole or mlky oil. This is due to the pump leaking and going into our oil since our water pumps are under the front timing cover like on the Ford 3.5 gasser. This can set VCT codes. Get a cooling system pressure tester and pump it up to the pressure on the cap and watch for leaks at the weep hole, etc.

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