1996 Geo Prism

[Team Zissou]

Anybody have experience with this year Prism or Corolla? My girlfriend's car has been exhibiting some overheating issues tied to the use of the A/C system. Basically, the temperature remains constant when the heater's blowing full force, but turn down the heat or the fan and the engine temp starts rising

Now the radiator fans are operating and I suspect they reduce their speed when the a/c system turns on, I don't have any idea what's wrong per se, but I plan to change the thermostat, flush the system and put in some Toyota red antifreeze and see if it gets me anywhere. Any other suggestions from the peanut gallery?

 

[Mace]

when was the last time the radiator was flushed?

Thermostat?

 

[Team Zissou]

2 years since the radiator was flushed, no data on the thermostat. Although she's definitely overheated the vehicle twice in the last 4 years- most recently last winter. Thermostat has not been changed since then which is one reason I'd like to start there.

I crawled the internet looking for Prism information that would somehow tie the a/c system in with the cooling system. The fans seem to be the only connection, but they work. Only other thing I can think of is if something is inhibiting coolant flow, but that would not be affected by use of the a/c system.

 

[Bob_Garrett]

Does it get hot if you're driving at freeway speed with the heater off? If it does, I would suspect a clogged radiator, as the fans don't help much then (and should shut off if not overheating). Also, if you have (or can borrow) an OBDII pc based scanner, you can record precise temps under varying conditions (idling, freeway, AC on/off, heater on/off, etc).

If the coolant is circulating through the radiator the thermostat is likely ok, but a new one would be worth trying. You should be able to use a Toyota one. Just get one for the same year Corolla. That way you're not relying on an aftermarket unit of unknown quality.

 

[Team Zissou]

I keep waiting for some unfreezing weather so I can flush the radiator with a garden hose, but I may take it to a shop. I suspect a clogged radiator as well but unfortunately do not have an OBDII scanner to check temperatures. Thanks for the suggestions all!