97 overheating

Fortunately, or maybe not, my heater control valve begins to leak antifreeze whenever the A/C is turned on. I brought my car in and they ordered a new one for me but I can't bring my car to get it put in until next weekend.

I'm driving the car without turning the ac on, and for the most part the temp. stays in the normal range. But sometimes it spikes and looks like it's about to overheat.

My question is, should I go ahead prepare to replace the thermostat too? Obviously I should wait and see if replacing the heater control valve fixes the spiking, but is it possible (since it's happened without the ac on, and without the leak (coolant level stays the same)) that the thermostat is broken too?

Just my humble opinion, but I don't think I would go anywhere with an over heating vehicle without replacing the thermostat first.

You're absolutely right. Normally the first step would be to replace the thermostat. But the coolant leak from the heater control valve is visible when the hood is popped and the a/c is running.

hey tell me if this sounds like your problem this is what is happening with my 1996 explorer that gage will go up to normal than in a few miles it will spike almost to hot than back done to normal again this will continue until I turn the control on the right to off than the temp runs steady in the middle of the gage if the control is on ac or heat vent or defost the gage is up and down .The things that I have allready tryed are changed thermostate flushing out the rad changed both rad hoses as they were collapsing when the temp would spike had two mechanics look at it for a cost of $90. maybe we are in the same boat .

...... but is it possible (since it's happened without the ac on, and without the leak (coolant level stays the same)) that the thermostat is broken too?


You do need to check the fluid level in the radiator when you have a leak and make sure it is full. You can't trust just looking at the overflow reservoir when you have leaks.

Your coolant temp sensor sits high in the engine, if coolant is low at all and you get air in the system it can cause spikes.

But assuming your cooling system is full, I think you would be wise to go ahead and do the thermostat since you have noticed that the spiking occurs even if the air is off.

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