I have a 97 GXE Auto with 130K miles.

I noticed recently that my cooling fans run constantly when the car is at normal operating temperature. When I first turn the car on when it is cold, the fans are off. However, as soon as the car warms up, they both come on and stay on, even it the car is just idling and the ambient air temperature is ~50F.

Also, if I start the car cold with the AC on both fans come on right away.

The upper radiator hose gets too hot to touch, while the lower radiator hose stays cool to the touch.

This is even after some very spirited driving.

The car never overheats and no codes have been thrown.

I thought it might be the ects (Engine Coolant Temperature Sensor) so I replaced it because it was the easiest thing to replace, but that made no difference.

Has anyone else had a similar situation? What was your remedy?

My thinking is:

Bad thermostat?
Bad fan relays?
Bad CPU?

Thanks in advance.

 

I'll let someone else handle this but the fans are supposed to come on when you turn the a/c on. Just a FYI.

 

The fans DO come on when I turn the AC on, my problem is that they stay on once the car reaches temperature and run constantly, even when the AC is off and it is relatively cold outside. They don't cycle on and off like they should.

 

sounds like there's a short somewhere. check the ects and fan harnesses.

at absolute worst, the fan motors will die and you'll have to replace them (which takes all of 5 minutes).

 

If there was a short wouldn't they be on even when I started the car with the engine cold?

After the car has been sitting overnight and I start it, the fans don't come on until the car reaches normal operating temperature, but then they never shut off.

Thanks!

 

good point. actually, it does sound more like a sticking relay. i'd still check the harnesses though. just in case.

 

Engine coolant temperature sensor or the relays.....or wiring from sensor to pcm

 

Definitely not the engine coolant temperature sensor. I changed that today and am still having the problem. I will replace the 2 relays and see if that fixes it.

 

Just do it (RELAYS)....if that dont fix it then I would check voltage from harness (5.0) means its good, otherwise pcm problem maybe or faulty ects you installed...check that(ECTS) also after harness check.

 

Did you replace the correct ECTS? There are two of them, one for the gauge inside the car and the other for the ECU. The one closest to the block is the one for the ECU, which controls the fans.

 

I used to have a 1997 cavalier where the fan ran all the time. the previous owner wired it so it would always stay on. Wired it straight to the fuse box in the car. If the fan wasnt on then the car would overheat.

My point: Maybe someone wired it to stay on permanently

 

Yes, I definitely replaced the ECTS. It was the one closest to the block.

 

I thought about that, but if this was the case, wouldn't the fan come on even when the engine was cold? As I mentioned above, the fan is off when I first turn the car on in the morning, but once it reaches temperature it comes on and stays on.

 

if thats the case then u most likely have an electrical / sensor issue

 

I don't have much experience with this issue but this statement here sounds like the key to your problem. Check the thermostat. From what I have read how it functions, it prevents the flow of coolant through the engine until it warms up. Now if it warms up and its not flowing like you stated here, I would say that its stuck.

 

I think id go with the fan relays first. They look to be sticking or something?

 

+2 replace T-stat and flush/backflush radiator.

 

There are two relays for the cooling fans one for low speed operation and one for high. You can usually swap a relay with one of the same type that controls another function such as wipers. That would help eliminate a sticky relay as the cause to the problem.

The ECU controls fan operation but it's unlikley that your ECU is bad.
What's strange is that even though you feel your engine may be overheating your temp gauge is normal and your check engine light is not turning on. The thermostat could be a problem but perhaps your fans are operation properly? The FSM has good informtion on fan operation in the EC section under Trouble diagnosis for overheat.

 

im having the same issue lmao...i just swapped the relays out (fan relay #1 was not hot-hot, but warm.) and i still have this issue. its weird because i dont go under my hood ever, only to add oil, or when i need to maintain something...and that hasnt been in about a month...and the problem happened a few days ago...so its not like i pulled on a harness or anything of that sort. i was thinking my ects, because about 2 months ago i changed my thermostat.

 

Just an update...... I replaced my ECTS and the 3 cooling fan relays and am still having the problem.

Next I will try changing the thermostat!

 

well...in your case of the upper being too hot, and the lower cold...check thermostat, cuz when the thermostat opens, the lower hose gets hot (of course)

 

Same thing I told him before in my previous post. He solved his own problem.

 

hmm...you mentioned that the top hose was hot to touch.
my hose is hot but hot enough for you to keep your hand on it.
it's possible that the t-stat could be bad and the ecu is preventing it from overheating.
odds are they're running on high too.

orrrr either you have air trapped somewhere??

 

Hi I am also facing the same problem.

Could you please tell me how to resolve this.

Mine is 2000 Nisan maxima GLE.

Thanks

 

I never figured it out. I still have the car, and the problem still exists, but as someone mentioned the worst that can happen is I have to replace my fan motors, which takes 5 minutes.

The electrical demons got the best of me on this one!

 

In the same boat. Replaced Tstat and hoses when water pump was changed, replaced ECTS and still fans turn on but won't cycle on and off as they should. Relays were swapped as well with a new one from OEM fog light kit.

Talked to a mechanic friend and he suggested it could be something with the auto climate control, have to follow up on that and will post here if I find anything.

 

I know you said you changed the ECTS, but to make triple sure you changed the correct one - was it the one with the 2 wires?

I would get an OBD reader that can tell you other things besides codes, specifically the water temperature (which is the ECTS reading) and see what the ECU thinks it is working with. On my car, the water temp is regulated at 198 degrees, rarely going more than a degree or 2 higher.

I don't remember if you said that you changed the thermostat. But the radiator hoses shouldn't have a lot of difference in warmth IF the water is flowing. Then there is the worst case senario where the impellor blades on the water pump are corroding off. This would also reduce the water circulation in the engine. It has happened.

photos courtesy of org member Nelsito65:

 

About the only way the climate controls (auto or manual) could do this would be for the controls to send out a false "a/c is on" signal. But this would cause the fans to be on as soon as you started the car.

Otherwise, the fans are controlled based on the ECTS temperature reading.

 

I think your on to something there.

Btw, how many miles are on that pump?

 

I don't know, Nelsito65 didn't say. I don't know if that was from his own car or one he was working on. I think that things like that are more of a maintence issue than age. The chemicals in the antifreeze were more likely worn out and depleted and not able to prevent the corrosion that ate the impellor blades.

When you look at the center hub of the old pump, it is coated with a brown slime. That should not be. I can guarantee you that every surface in that cooling system was coated like that. That junk would be in the radiator and when you took the cap off, it would be on the bottom of the cap. He may have been running straight water in that car but definitely not good, healthy antifreeze. That's why you need you change your antifreeze every so often.

 

Remove the radiator carp and turn the engine on and let it idle for a while so the thermostat can open and the cooling system can circulate. There could be air bubbles stuck in the system. Try a new cap too.

 

You've been here long enough to know the rules about bumping old *** threads. Lol