Turning the heat on brings it down very fast. Is that just because of where the sensor is, or is it really cooling the engine coolant?
Does all this point to the need for a radiator flush or what?
Things to check. First one first: Radiator fins clogged with dirt and debris. Thermostat may not be opening all the way. Radiator fan (or fans) may not be turning on. Temp sensor (or sensors) may be going bad. Hoses may be collapsing. Cooling systems rarely clog up, unlike in the old days.
Maybe one of the easier fixes. It's amazing how far you can throw a malfunctioning thermostat when you really want to.
Thanks!
Thanks again. It was the water pump.
Tom, thank you for the update. It's been so long since I've replaced a water pump that I had completely forgotten about that part.
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