Car runs hot when ideling

I'm wondering if the fan is intermittantly cutting out while its sitting in traffic. Simply gets hot and stops working?

How is it cruising down the highway? If its fine at highway speeds, but problematic sitting still, the first things I'd look at are the radiator itself and the cooling fan. Bent fins, bugs, cooling fan intermittantly working.

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This could be the problem. Is there a pattern I should look for to indicate something with the fan is bad? Should I try changing the relay? Any test i can do with no equipment (just basic tools)?

Again, at highway speeds the temp goes up to about 220 then suddenly drops. My radiator is new and the problem existed with the old one and is still there with the new one. I don't have a lot of money to shotgun this thing so I am hoping to get some ideas on how to isolate the problem. How should the fan work? Should it just kick on at a certain temp then cut off at a certain temp? I did notice, sitting in the driveway, it kicks on for approx. 5 secs periodically as the temp is going up to operating temp then shuts off. Is this normal? Not sure how to test going down the road?

Soapm wrote in alt.autos.gm

You said nothing about the thermostat. Replace that, they are cheap and easy. And when you refill the cooling system make sure the car is pointing up hill so that the radiator cap is higher than anything else on the car. That should eliminate any air bubbles. Just because you flushed the cooling sysem, or had a pro do it, does not mean that all the bubbles made it out of the cooling system.

The electric fan should kick on and run until you notice your temp dial drop (so it should remain on as long as engine temp. is high enough). So, the next time the fan is on, check your temperature gauge. The switch for the cooling fan also locates on engine near thermostat housing. Perhaps your fan or temperature switch for the fan is defective that is if your electrical wiring and contacts is proper condition Paul

If this has dual cooling fans like the later models, the right fan should be on and the left should be on at low speed at 212, and the left side fan should go to high speed at 226. You should make sure the fans are running and stay running when the engine gets up into that temperature range.

It might also be something like a cooling system restriction or partly sticking thermostat..

Ever change the thermostat?

Thanks for all the help Guys. Sorry it takes me so long to reply but my ISP's NNTP server (reader.news.uu.net) has only read capability. This means I cannot reply until the message has archived on google. I guess I am also in the market for a free NNTP server that will allow me to post.

Anyway, I am going to change the thermostat and the cooling fan switch. Sounds like I can spring for these and a gallon of antifreeze the next time I get paid. Sucks being poor! If I had J-LO's engagement ring then I could take my car to the shop to get it fixed...

I got a chance to take a good look under the hood today and had no problem finding the thermostat housing. I am guessing the brass colored screw on top is for bleeding the air from the system. Right?

However, I don't see any stinking fan switch. I don't aven see the temp sending unit. Can someone point me in the right direction?

There won't be an actual fan switch, the cooling fans are controlled by the ECM based on the coolant temperature sensor input. However, older GM vehicles often had two sensors, one for the gauge and one for the ECM. Usually on or near the thermostat housing, though they could also be in the cylinder head somewhere..

Ok, I changed my thermostat and the problem has changed a bit. Now it sits steady on the 200 degree mark while I am driving which is a good thing. i took a good drive on the interstate and she sat at one temp the entire time. I thought it was fixed. Then I stopped at the KFC drive through the temp gauge began to climb again. I also noticed that the fans were not on. I am saying this because I could not hear them and the roar they make by sticking my head out the window. I pulled to the side and opened the hood and the fans were on and the gauge began to go down.

Could it be my fans are not working right while the car is in Drive but come on when I put the car in park? Could it be that the fans work on low but not high?

Is it possible that at highway speeds the fans didn't need to run? Then there was a mild delay between that and the car figuring out it needs to run it. Maybe you just noticed the temp clime a bit during the delay?

Correct, the fans will not have to run at highway speeds. When you stop, the temp. climbs, calling for the fans to run. If you run the A/C however, the fans will run. I'm not sure if they both run in A/C all the time, or only when you're in recirc. mode.

Ok, thanks for all the help. I am almost certian my problem is with the fans. I let the car idle in the driveway until the temp got almost to the red line. Then I cut it off. The fans never turned on.

From what I can tell this leave 3 things that can be the problem. The computer, the temp sensor and the fan relay. Just below my radiator cap about half way down the radiator there is something with wires running to it. Could that be my temp sensor?

Also, I located my relays, they are on the firewall behind a cover. How do I tell which relay controls the fans?

This is a 92 Pontiac Bonneville SSE (no super charger) with 3800 engine.

thermostat

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