Radiator cooling fans are on all the time - Page 2

BNaylor · #16 03-04-2006, 08:02 PM

Quote:

Originally Posted by birdboyd

Latest update:

I took the car into a shop and had it hooked up to see what the problem is. What they came up with is that it needs a new temperature coolant sensor. They said that the sensor would not send a signal or one that did not make sense to the computer, which would then turn on the fans to "protect" the engine, figuring it is better kept overly cool. This would be consistant in what GregA has said. They also said that a new thermostat was needed.

I am not sure about this diagnose. I checked the resistance of the sensor in the car and it checks out fine. They said they checked out something with a heat gun and it was not reading correctly. Other than that I guess it could be a possiblity. I don't belive it about the thermostat because that seems to be working like it should.

After they checked it they cleared codes. Now it is working again. I am reluctant to change the sensor until it acts up again. If I change it now and it works I will be wondering if that was the fix, or if just decided to quit acting up.

Anyone have any comments or things I should try?

I'd replace the ECT (engine coolant temperatue) sensor if it acts up again. Resistance can check out but it is a static check only. The PCM provides 5 volts to the ECT sensor and then the sensor sends the signal with a voltage drop back back to the PCM. It could be noisy or probably more like no signal. Maybe the electrical connector was flaky.

If you disconnect the ECT the fans will run on high all the time probably for safety purposes.

birdboyd · #17 03-05-2006, 09:03 PM

Thanks once again for your advice bnaylor3400. I think it is starting to make sense. I still want to wait until it acts up to replace it. As a learning experience I want to know for sure that is the problem. If I replace it before it starts to act up I will never know if that was indeed the issue. I think it might be though. I still say they wanted to replace the thermostat as an "add on". It seems to be working as designed.

jc83 · #18 03-07-2006, 06:29 PM

the temp sensor is mounted on the side of the radiator below the fill cap...its tough to see...mine used to set off the fans alot....i went to a pickapart junkyard and got a good one instead of paying big bucks from gm and it solved the problem...ps i believe there are 2 temp sensors in the system..1 on the radiator and the other on the block somewhere..?? good luck

BNaylor · #19 03-07-2006, 07:05 PM

Quote:

Originally Posted by jc83

the temp sensor is mounted on the side of the radiator below the fill cap...its tough to see...mine used to set off the fans alot....i went to a pickapart junkyard and got a good one instead of paying big bucks from gm and it solved the problem...ps i believe there are 2 temp sensors in the system..1 on the radiator and the other on the block somewhere..?? good luck

I really don't agree with that. The sensor on the passenger side of the radiator is the coolant level sensor. See pic below. The ECT (engine coolant temperature) sensor is located below the thermostat housing and helps the PCM control turn on/off of the fans.

First off that is not what the GM Grand Prix service manual shows. To test what I am saying, disconnect the ECT and the fans should come up in the high speed position for safety reasons. If you disconnect the electrical connector at the coolant level sensor it won't do anything. It won't even cause the fans to come on or turn on the coolant warning light. The coolant warning light needs a ground applied to turn on. However, both sensors may trigger the coolant warning light when conditions are met like low coolant level and/or overheating.

richtazz · #20 03-08-2006, 06:03 AM

I agree with Bob (bnaylor)that even though the ECT is checking ok on the bench, it may be breaking down under exposure to heat. I would change it if it acts up again, and if you haven't changed the T-stat within the last year, do it too while the cooling system is open. I change my t-stat every spring as regular maintenance(while checking cooling system for sludge and dirty coolant). Most people don't realize that a T-stat doesn't just open and close once. It can open and close (partially) 10-15 times per minute to properly regulate coolant flow and temperature. The bi-metal spring takes quite a beating, and can become slow or weak, restricting flow, not completely closing, or not completely opening. This could cause many problems, like weak heater output, running hot, etc.... Just my

jc83 · #21 03-08-2006, 09:54 AM

sorry screwed up-- your right-- what it did (coolant sensor) at the time was allow the temp to go to near the redline on the dash temp gauge...this happened a few years ago forgot the specifics of my story..sorry for confusing you..

canadian guy · #22 03-08-2006, 06:46 PM

sounds to me like whoever flushed the rad might have got debris on the end of the coolant temp sensor, u can try to remove it and clean it if NOT replace...should solve the problem....

birdboyd · #23 03-09-2006, 07:20 PM

New update 3/9/06---

Replaced the coolant temperature sensor. Torqued it down to spec found in one of these posts. Although tempted, I did not use teflon tape, per another thread due to the NPT threads. Hooked everything up and fans still were on. So was the SES light. I did notice that the temp gauge was reading warmer then before, but well within limits.

Took it to Autozone to read codes. Code read PO128-- Coolant temp always low. I told them to clear it and they responded that they couldn't due to emissions laws now. I decided that it would be worth while to rent a code reader while I was there and clear it. Once I did the fans went off.

That was yesterday. Today the car came home and the fans were on again, but no SES light. Hooked the scanner up and same code popped up. Cleared it and fans are off.

Started scratching my head. The book with the code reader said to check thermostat, it could be defective. I thought it was working, but now I don't. The first thing I noticed is that the upper hose was hot, but the lower hose was cold, and so was the radiator cap after 25 minutes of driving. It does not seem like it is circulating. So my thoughts are that it works once in a while, and the fans turn off when the PCM senses the correct temp. It gets stuck closed and the PCM reads cold temps, and throws on the fans for fail safe.

Could this be right? Could it really be something like this that I should have originally checked for? My other thoughts are that some Dexcool sludge got built up in there, or when I had the flush done it all collected in there.

So the way this car is set up, with the 3.1L, what do you think? There was no build up on the old Coolant sensor. Looked like new. Is there any other tests I should do on the thermostat?

Thanks again for everyones help. I am just trying to figure things out. I hope this is coming to an end. At least I am learning alot about my car!!

wlkjr · #24 03-09-2006, 09:12 PM

Could it be that coolant level sensor mentioned above? I believe if the thermostat was stuck closed it would overheat very quickly and blow steam. May only be opening partially.

birdboyd · #25 03-09-2006, 09:22 PM

Oops-- actually I meant to say stuck open. That way it is in a constant loop and doesn't have a chance to build up pressure or heat.

BNaylor · #26 03-09-2006, 09:50 PM

Quote:

Originally Posted by birdboyd

Oops-- actually I meant to say stuck open. That way it is in a constant loop and doesn't have a chance to build up pressure or heat.

If the thermostat is stuck open I would agree with the DTC error code you are getting and go with Rich's suggestion to change out the thermostat.

birdboyd · #27 03-09-2006, 10:03 PM

Is there an in car test I can do on the thermostat? I don't want to rip it out until I know for sure. However searching other posts seem to point to a bad thermostat also.

BNaylor · #28 03-09-2006, 10:15 PM

Quote:

Originally Posted by birdboyd

Is there an in car test I can do on the thermostat? I don't want to rip it out until I know for sure. However searching other posts seem to point to a bad thermostat also.

Not while it is installed. When pulled out you can visually inspect it. If stuck open you will see it stuck open. The test was putting it into a pan of water on the stove and heating it up while monitoring with a temperature gauge. But that was to test the opening point. If stuck open it would be moot to test anyways. Good luck!

birdboyd · #29 03-31-2006, 08:14 AM

Good morning,

Sorry I did not get back with the fix. After guessing for so long I believe I finally have it fixed. All it turned out to be was a bad thermostat. It was not allowing the car to get up to temperature. The computer would sense that the reading was wrong for how long it was running, and would throw the fans on to protect the engine. I now have a new thermostat and temp sensor (just in case) installed and it has been fine for two weeks now.

I would like to especially thank bnaylor3400 for his time and guidance. It is users like you (and many others) that make me happy to use this board.

birdboyd

BNaylor · #30 03-31-2006, 09:44 AM

Quote:

Originally Posted by birdboyd

Good morning,

Sorry I did not get back with the fix. After guessing for so long I believe I finally have it fixed. All it turned out to be was a bad thermostat. It was not allowing the car to get up to temperature. The computer would sense that the reading was wrong for how long it was running, and would throw the fans on to protect the engine. I now have a new thermostat and temp sensor (just in case) installed and it has been fine for two weeks now.

I would like to especially thank bnaylor3400 for his time and guidance. It is users like you (and many others) that make me happy to use this board.

birdboyd

You're welcome and glad you got it resolved. Thanks for the feedback.

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