HELP! Overheating problem has me worried 1989 Cultlass Calais

[amyindallas]

I have a 1989 Cultlass Calais 2.5 with 83k original miles. I bought the car in Feb. from an old man's daughter after he died. I have had no problems until recently. Saturday I had the oil changed and the guy said I really needed to get my radiator flushed and the water was a nasty brown color. I had planned to have that done on Tuesday anyways so I waited. I took a 3 hour trip (each way) on Monday and it was about 95 degrees that day. I drove all the way with the AC on and had no problems. On the way back, after 2 hours I stopped for food. There were no lights on the instrument panel on to let me know that there was a problem. As soon as I parked and turned the car off, a huge amount of the dirty water came gushing out. OVERHEATED. I waited until thecar cooled off and filled the radiator full of water and put on a new radiator cap (there was a hole in the old one) and drove the rest of the way home with no problems. I drove 55 MPH, no AC, and it was considerably cooler. Then, I got a new thermostat installed and got the radiator flushed and filled. Today, I am driving to work, it's hot, I have the AC on and after about 10 minutes of driving, I'm stilling at a red light and the idiot light comes on. I immediately turn the AC off and turn the heater on and the idiot light instantly goes off. I thought maybe it could be the fan but the fan is working. It does NOT (and has never since I have had the car) stay on constantly..just when it needs to. I'm thinking it might be the waterpump. But I have been dribing the car a week since the first overheat...would I be able to drive for a week with a bad waterpump??? What else could be the problem? I just feel that even if it's hot, I should be able to have the AC on and NOT overheat. Please help!! Thank you in advance.

Amy

[Slade901]

I'm just hoping you don't have a head gasket leak.

You can try to use a 70% coolant and 30% water mixture for higher temp protection as well as lower temp protection.

I would however remove the two coolant temp sensors and clean them first the put them back and and then test it. One of the coolant sensor is usually on radiator itself and the other one is behind/below the throttle body intake.

When you fill the cooling system, make sure you turn the bleeder screw above the thermostat and open it until coolant is flowing out of it without any bubbles.

You can rig the fan with a manual switch to turn it own while on a traffic stop and go.

Check this link http://www.thirdgen.org/tech/cool8dual.pdf

http://www.babcox.com/editorial/tr/tr110046.htm

Check this link about installing a manual fan swtich. It will give you an idea how to do it on your vehicle.
http://www.v6z24.com/howto/fan