car engine overheating

[HornOnTheBayou]

My fiancee's has a 97 Neon and the engine has been overheating the last two days. When I turn off the AC, it goes back down a lot. I know turning off the AC is supposed to help it a little bit, but the temperature gauge is going down to well under the half mark. Is that normal? The reason I ask is because she recently had the AC worked on and I wonder if something happened. Anybody have any insight?

 

[horn1]

thermostat problem?

 

[TxStHorn]

Check the radiator fluid, first. It sounds backwards, but more water and less antifreeze will actually make your car run cooler.
If fluid level's good, look to the thermostat, then the sending unit for the gauge.

 

[horn4life]

How well is the AC cooling? I am assuming you have electric fans that pull air across the radiator ond AC condenser.

I also wonder if you are talking about turning off the AC while sitting in heavy traffic or at low speeds? If the car runs cool when moving at higher speeds but heats up at lower speeds it's probably a fan problem or a thermostat problem not allowing the coolant to flow in a cycle

Check you fuses for the fans first as it's as easy as anything

 

[MrPhlegm]

While you're looking at the antifreeze check to make sure that it dosen't have oil in it. If it does, trade that sucker in cause you could have a blown head gasket, very expensive.

 

[hollisdude]

hahahahaha - blown head gasket. I've been there and it is correct, that is an $1800 job if it is.

 

[accuratehorn]

I think the car has two electric fans, like Hondas. If so, one is probably inoperative. Or if there is just one, it may be inoperative. The car will cool ok going down the road due to air flow over the fins of the radiator, but will overheat when stopped.
The relay, thermostatic switch, or more likely the fan motor is probably bad.

 

[HornOnTheBayou]

Thanks for the thoughts.
It's not overheating at low speeds. It happened Monday when we were driving on the highway from Galveston to Austin.
I'll check on the other stuff when she gets home from work.
But does anyone think it has something to do with the AC being fixed? Maybe I'm crazy and grabbing at straws, but I've been thinking about it.

 

[accuratehorn]

If it tends to overheat more on the road than at idle, then it is not the fans. It would tend to be a clogged up radiator, partly stuck thermostat, or slightly leaking head gasket. Start with a new thermostat. The old one may be broken-you can see a break in the metal when you take it out.
Shouldn't have anything to do with fixing the A/C, except there is more heat to remove with the A/C operating.

 

[BigWill]

or maybe the mechanic pulled a fan wire while working on the AC.

 

[TxStHorn]

I would not be inclined to beleive the overheating was due to the AC repair - I suspect it's either coincidental, or the mechanic failed to put something back properly.