91 Toyota Corolla Overheating


Hello, Everyone.

I always appreciate your help here.

My 91 corolla recently got little bit overheating problem. Maybe 3 wks ago, radiator hose blew up, so that I replaced it. (I don’t think that this is related to overheating though. Just in case).

Anyway, I fill the coolant with distilled water. Maybe 1 wk ago, I noticed that my temperature gauge went up much more than usual, not in really high area though. It happens that if I drive 75-80 mph, it goes up more. However, if I drive 65 mph, the temperature went down little by little. Somtimes, when I drive in local way, the temperature goes up. I don’t know what caused it. Oh, more than half time, when I drive back home, I found out that there was boiling sound, so I opened the hood, and I found out the Coolant was boiling with steam out of it. I added up more water always it happened. I checked the radiator fan, fan is working, the way I checked the fan is when I turn on the AC, ac fan right in front of radiator works, and then big fan works later.

What I remember is that (not 100% sure though) even when I turned the engine, and put key still in, radiator fan was still working quite long. However, now, if I do samething, radiator fan stopped maybe 20 secs later.

Is it something in the radiator? or my radiator fan sensor or motor went bad?

Thank you very much for reading, and thank you in advance for your answer.


Well, I forgot to say that I saw the bubbles streaming through the overflow bottle.


I’d bet that you need a new thermostat. If it’s never been replaced, 16 years is a LONG time to go without needing one, but by now you probably do.

$5 part, 10 minute job. And don’t fill your cooling system with distilled water; use a 50/50 mix of ethylene glycol (green stuff) and water. Otherwise the coolant will boil away too quickly.


Water is not a substitute for coolant. “Antifreeze” is not just to prevent freezing, it lowers the boiling point and carries more heat than water.


Could it be leaking head gasket? (I hope not). I think that I saw that somewhere here in this forum.


First I’d try changing the thermostat and filling with 50/50 anti-freeze and water. You can buy it pre-diluted, but it’s not much, if any cheaper, kind of a waste, but anyway… try this first. But you might need a head gasket.


Well, I went to machanic today.
I’ve changed radiator cap with pressure release knob, and fill the coolant twice so far.
Everytime I filled the coolant top, it seemed like that there was no overheating problem. I mean the first ride after coolant filling, it looks like there was no problem. However, after first ride, again, overheating problem happened.
Anyway, mechanic told me that since radiator hose is hot, therefore no thermostat problem. and also he said it does not look like leaking gasket since idle sounds good, and there was no white in the exhaust gas. Anyway, he did pressure test, and he found out the radiator hose I changed 3 wks ago was leaking. so that he fastened it, and he did powerflushed radiator. and he also told me that I’ve lost 1 gallon of coolant. He testdrived for 10 miles and there was no overheating. I was so glad at that moment.
Anyway, I picked up the car, and went back to home in stop and go traffic. WELL, there was overheating problem gain. I had to turn on the heater to cool down the temperature here in texas.
What could be a problem? what do you think? any help?
I’ll go back to the mechanic tomorrow.
Thank you very much.


Please somebody help me!! Thank you.