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In the summer 2008 I had my entire cooling system replaced.  About ten days afterwards the overheating problem disappeared only to return in the summer of 2010.  To make a long story short, it was the cooling fan relay that needed to be replaced.  Now the car is running like a champ!  -  Bob the finder www.bobthefinder.com  

did this compleatly fix the problem after you replaced everything?  

This is a little late but I have your fix. The engine coolant has to pass through the Heater Core before it gets to the Thermostat. Disconnect the hoses to the Heater Core and flush it out or replace the Heater Core and your done. GM used this design to speed up in-cab heating.    

I have been fighting this problem for 5 yrs. Its always the simple things. Went through all the same things, radiator, relays. Rework the connections on the bottom of the fan relay! Actually runs a little cool.  

After 5 yrs fighting this problem, rework the connections on the cooling fan relay. Or replace the socket. I spent a lot of money, seems its always the simple things. Now i think its running cool, probably because i was used to it running hot! The fan kicks on now as soon as i turn on the ac and the fan kicks on about mid range. Good luck.  

rsuchland:
After 5 yrs fighting this problem, rework the connections on the cooling fan relay. Or replace the socket. I spent a lot of money, seems its always the simple things. Now i think its running cool, probably because i was used to it running hot! The fan kicks on now as soon as i turn on the ac and the fan kicks on about mid range. Good luck.

rework the connections on the cooling fan relay. Or replace the socket.

thank you for this....

its going to help a lot.. as those sunbirds have been known for being almost impossible to cool....

       
this is what the relay looks like....



this is the straight on look at the relay pin...




30 and 87   are the contacts... that open and close...

85 and 86 are the coil windings... that operate the relay...

i have used a strong needle pointed  device to close the grip on the connector terminals where the relay plugs in at.....  

Well, I have a '98 pontiac sunfire(2.2L OHV) and my problem is completely different. My Sunfire overheats when I am sitting idle but also when I run at anything above 65mph. When it starts to over heat when I am idling, all I have to do is drive it. I don't know what to do about that. But also, why do you think it overheats while I am driving at these speeds? I also am not sure if it is supposed to have 1 or 2 cooling fans. Oh, and what the hell is the switch on the turn signal that says,"R/A on /off". Thanks!  

Well, I have a '98 pontiac sunfire(2.2L OHV) and my problem is completely different. My Sunfire overheats when I am sitting idle but also when I run at anything above 65mph. When it starts to over heat when I am idling, all I have to do is drive it. I don't know what to do about that. But also, why do you think it overheats while I am driving at these speeds? I also am not sure if it is supposed to have 1 or 2 cooling fans. Oh, and what the hell is the switch on the turn signal that says,"R/A on /off". Thanks!  

Well, I have a '98 Pontiac sun-fire(2.2L OHV) and my problem is completely different. My Sun-fire overheats when I am sitting idle but also when I run at anything above 65mph. When it starts to over heat when I am idling, all I have to do is drive it. I don't know what to do about that. But also, why do you think it overheats while I am driving at these speeds? I also am not sure if it is supposed to have 1 or 2 cooling fans. Oh, and what the hell is the switch on the turn signal that says,"R/A on /off". Thanks!  

Well, I have a '98 Pontiac sun-fire(2.2L OHV) and my problem is completely different. My Sun-fire overheats when I am sitting idle but also when I run at anything above 65mph. When it starts to over heat when I am idling, all I have to do is drive it. I don't know what to do about that. But also, why do you think it overheats while I am driving at these speeds? I also am not sure if it is supposed to have 1 or 2 cooling fans. Oh, and what the hell is the switch on the turn signal that says,"R/A on /off". Thanks!  

Well, I have a '98 Pontiac sun-fire(2.2L OHV) and my problem is completely different. My Sun-fire overheats when I am sitting idle but also when I run at anything above 65mph. When it starts to over heat when I am idling, all I have to do is drive it. I don't know what to do about that. But also, why do you think it overheats while I am driving at these speeds? I also am not sure if it is supposed to have 1 or 2 cooling fans. Oh, and what the hell is the switch on the turn signal that says,"R/A on /off". Thanks!  

well..

there seem to be 2 different radiator cooling fans...

this one for cars with AC  





this is what's shown for cars without factory AC..




does your radiator cooling fan cycle on and off... then back on.???   is the fan blade actually pulling air through the radiator ...

wiggle the fan blade.. is is properly attached to the radiator fan motor...   the center is not burned out of the plastic???

the radiator fan is controlled by the cooling fan relay...   and thanks to the previous posters...  they have pointed out that there are problems with the relay socket..  that there is not enough grip on the relay pins to send enough power to spin the fan at full speed...


now... with your car.. overheating at idle and at high speed....   i have seen that before...  and several things could be happening...    the OEM temp for that model is 180F... not 192 like almost any other car...



people have removed the thermostat to fix cooling system problems...  this just does not work with cars equipped with electric cooling fans...   without a thermostat.. the coolant will circulate without stopping..    normally the thermostat  stops the water flowing through the radiator as the radiator fans are cycled on by the computer..   this stopped coolant can now be cooled by the fans....  without the thermostat controlling the flow through the radiator.. the coolant will be flowing so fast.. there is no chance of the coolant ever being brought down in temp... so at low speeds where you have NO ram air cooling.. it will eventually overheat.. and at speeds above 55 usually.. yours seem to be 65.. the coolant is passing through the radiator so fast that even the ram air cannot take the heat out..


another thing that can cause overheating problems...  improperly installed radiator caps.. or defective radiator caps that don't hold pressure..   the system has to operate at 13 to 16 pounds pressure ... if it does not.. the system can boil the coolant inside the engine.. causing steam bubbles to form..  

if you don't have a 50% to 70% mix of coolant to water...   you can have an overheating problem..


OH the letters on the turn signal switch...




thats for the cruise control....      do you still have the Owners manual in the glove box..   its explained in detail how to work them properly...     stepping on the brake will cancel the cruise control..    please drive with it in the OFF position..  so there are no mistakes..

R/A      Resume/Accelerate

on/off of the Cruise control.....


overheating diagnosis on your car is really going to take a few tools...

a professional scan tool..  most generics will NOT do what needs to be tested..  professional model scan tools can test the radiator cooling fan circuit by requesting the computer to turn it on... and off...

you can with a generic scan tool.. watch the engine coolant temps  on the ECT display on the scan tool.. this is a different circuit usually than what is displayed on the dash board..

you will need to verify the cooling system is operating.. by monitoring the temp of the parts on a cold start...   since you cannot see the coolant flow through the radiator .. you can feel that the engine is building temp.. but the radiator stays cold until the thermostat opens around 180F... then the radiator should get hot and the engine should cool off a few degrees.. at this point the radiator cooling fan should come on..    run for 30 seconds to a minute.. then shut off..   the temp will come up again and the fan should come on again..  for 30 seconds to a minute... then shut off...

after the first cycle..  you won't be able to feel the difference in the temps..   you will need a 30 to 40 buck infrared non contact thermometer like this... there are cheeper models.. be sure that the high temp shown on the box is above 250F or its really worthless for working on cars..  i spent 60 bucks on the one i use.. it is good for almost 1,200 degrees.. but then i do this for a living.. real professional models can cost up to 200 bucks...  do the same as the 30 or 40 buck models..



or this..

 

oh... if you have the smaller of the radiator cooling fans.. it sure looks like the AC version is a direct fit..

what's funny.. the ac version seems to be a few bucks cheeper.. at least at AZ.. in dorman brand..


its probably relay 20...  but check your owners manual...



this is the relay.. i have not found individual components for the socket..   so you will have to use thin pointy tools to probe them carefully to tighten them....
RELAY,FAN CONT ACDelco #15-8733) GM 12193604  

Do you have heat? Heater core has coagulated coolant and needs to be flushed or replaced.