Engine Overheat

My cars temperature gauge goes to the upper limit of normal before it comes back down and then starts over again. Suggestions have been fan clutch. Could this be thermostat or the gauge sender?

The most liekly candidate is the T-stat…assuming you’ve already checked your coolant level. Have you?

Coolant Level is good. I will go with the t-stat.

It could be air trapped in the cooling system. If there’s air in the cooling system and it gets to the water pump, it can cause the coolant flow in the engine to stall where it starts to overheat. Once the air leaves the water pump the coolant starts flowing again and the engine cools back down.

To remove any trapped air, get the engine up to operating temperature. With the engine idling loosen the upper radiator hose clamp. Take a small flat bladed screwdriver and slip it between the upper radiator hose and the radiator hose neck. Allow the engine to idle until nothing but coolant comes out of the upper radiator hose. Retighten the hose clamp.


I’ve never thought of that but boy it could explain my problem. I’ll check that first.

nice tip, thanks.

Turns out there was no T Stat installed. Flushed out radiator, installed TStat, things were running cooler. Driving to work this morning, engine went into serious overheat, head gasket blew. Let you know what the garage finds.

What year car? How many miles on it? Head gasket was probably on it’s way out. No thermostat wouldn’t cause overheating.


The reason no t-stat was installed was because someone had already determined the overheating “issue” could be “fixed” by removing the t-stat and mask the leaking head gasket.

Wild swings in temp are due to hot combustion gases leaking into the coolant by means of a crack or failed head gasket.


It is likely that if the engine got too hot, both gaskets are in jepoardy of failure. (Left and right heads.)

Good luck,


I agree wholeheartedly with Matt’s suspicion that the T-stat was removed by someone to try to cope with a chronic overheating condition. Your adding the T-stat beck in made the situation worse.

A blown headgasket is a very real possibility here. Verification can be accomplished by checking the coolant for the presence of hydrocarbons, by doing a pressure leakdown test of the cylinders (the true definitive test), or by removing the radiator cap, running the engine, and watching for bubbles in the coolant in the fill hole. Those would be the combustion gasses being blown into the water jacket and migrating up to the system high point, the fill hole.

While you very likely have a blown headgasket now, it’s also possible that some other problem is the real rot cause. A clogged radiator, a water pump with eroded impellars, a T-stat that had stuck, a collapsed hose liner. any of these could have caused overheating with subsequent head warpage and/or breeched headgaskets.

I think it’s important to have the overall system and engine evaluated if you’re to truely solve the problem properly.

This cloud has a silver lining. I suspected the T-stat had been removed for the reasons stated above but indications after the coolant flush and new T stat it was safe to drive. The garage confirmed blown head gaskets. We are somewhat mechanically competent but the age of the car (93) and my work schedule, prevent replacing the gaskets and discovering the cause myself. I’ve traded it (after owning it for one week) to the garage for a road ready 96 Cougar (restored by the garage). Perhaps wiser heads would have not gone with this 93 car, but I needed transportation really bad. I’m moving on poorer but wiser. Thanks for the great advice and information. This is a great site.

Thanks for posting the conclusion. Most of us here hang out here because we enjoy the technical challanges and because we enjoy helping people. It’s good to hear the final result occasionally.

I guess the truth is that you’ve just borne the cost of a bit of education.

Sincere best.