View Full Version : heating/cooling question

10-31-2008, 06:56 PM
so i was doing a simple lower radiator hose and thermostat today on my car. everything went okay. but im still wondering why the fan kicks on when the car is about to over heat. the fan does work but idk where the problem might lie. coolant temp sensor maybe? fan relay?

any advice or guesses?

thanks in advance

Duffy Floyd
10-31-2008, 06:59 PM
Which fan? The main fan starts in slow at 222F degrees and shift to fast at 226F degrees. Depending on the pressure in the coolant system that isn't all that far from the boil point.

10-31-2008, 07:03 PM
i did notice there was 2 fans. i think one is for the AC its in front of the radiator and IC. the other one im guessing is the main one that sits in front of the water pump/crank area. i cant tell if the front one kicks on or not. but the main one kicks on at high temp.

Duffy Floyd
10-31-2008, 07:49 PM
The pusher fan is in front of the radiator and is an over temperature fail safe fan. The main fan to the rear of the radiator operates as described.

11-03-2008, 06:30 PM
i see. thats the fan that kicks on when the car is about to over heat (about 1 CM away from the red line on the temp gauge) any other time it doesnt kick on. i talked to one of my friends he said it might be the fan relay or the coolant temp sensor. is it a possibility? or another problem that im overlooking

11-06-2008, 09:16 PM
Replace the coolant temp sensor they have a tendency to get lazy with age fan should kick in around 220 or so. Replace the radiator cap as well as the system needs to maintain the proper pressure to function properly.

11-08-2008, 04:20 PM
The fan relays are contained in the IRCM box just behind the driver side headlight.

Typically you can check to see if the low speed fan winding is working by turning on the A/C when the engine is running. When the A/C is turned on, the EEC will tell the low speed cooling fan winding to energize.

If the fan doesn't come on, you should track that down first. If it does come on, but you still don't notice a fan until engine temp is high, then you can try changing out the temperature sensor for the EEC (not the one for the gauge). The EEC temp sender is left of the blower snout, the gauge sender is on the thermostat housing.

11-22-2008, 05:46 PM
so im having yet another coolant problem.

i havent changed out the coolant temp sensor yet. moneys been tight cause of bills and holidays. but will do it next week.

im not sure whats going on, but the low coolant light comes on and off once in a while, it started like 3 days ago. i made sure that the radiator and overflow tank are ful, and they are.

could it just be a bad sensor? and if so witch one?

thanks for all the help. if it wasnt for alot of you knowledgeable SC guys, id be stuck.

11-22-2008, 07:28 PM
There is a float style sensor directly in the coolant reservoir. Not sure what would cause it to flicker. You can try and re-seat the connection and see that clears it up.

11-22-2008, 08:26 PM
>There is a float style sensor directly in the coolant reservoir.

My 1990 SC w/VMM has a dual-contact submersible probe that is attached to the top, extending down low in the coolant expansion tank.

The contacts rely on coolant/water to conduct electricity between them and if they aren't bathed in coolant, the circuit turns on the low level warning light - I've seen these become covered with deposits over time that can eventually inhibit current flow between them, triggering the low coolant indicator in the VMM. With our cars seeing so many years and miles, it should be no surprise that this type of component needs a bit of attention.

The sensor probe can be removed (pried out...note any index tab) from the top of the expansion tank - use caution, as the leads from the top of the probe to the contacts are sheathed with plastic insulation that can be easily cracked/broken (due to age/heat) - this can leave the leads exposed - suggest resealing with silicone. This could also be a good time to remove and muck out the expansion tank if it contains any sludge, etc.

Carefully scrape or wire brush any deposits off of the inside & outside face of each contact and then reinstall into the coolant tank and reconnect the harness. Fill the expansion tank to the right level and check for proper warning light operation.

If the contacts on the end of the probe are clean, check the circuit at the probe connector.

11-23-2008, 01:27 PM
>There is a float style sensor directly in the coolant reservoir.

My 1990 SC w/VMM has a dual-contact submersible probe that is attached to the top, extending down low in the coolant expansion tank.

good to know. I haven't taken mine apart, but due to the size of the fitting on the top figured it was a float style like the sensor on my wife's durango for low washer fluid.