Cooling fan problem

[Rock_28]

2000 GP SE 3.1l Neither one of my cooling fans are working at all. I checked the fuses and they seem to be fine. Any ideas On what could be the problem. I just changed my first and hope only last manifild gasket and plenum seals and it turned out perfect but now when I'm stuck in traffic my temperature needle nearly hits red. Fans definitly are not working.

Rock

[richtazz]

How quickly does it heat up from cold? Did you bleed the air from the cooling system after replacing the intake gaskets? Did you install a new t-stat while you had it down?

The fans are factory set to come on at about 230 degrees. They should come on regardless of engine temp (once it's warmed up and in closed loop mode) when the AC is set to max. If they still don't come on, then you need to check the relays in the underhood fuse/relay center. If the check engine light isn't on, then I would rule out the coolant temp sensor, as the same sensor is used for both PCM fuel management and fan turn on.

[Rock_28]

it heats up and stays at 210 while i'm driving and then when i'm stuck in traffic it heats up slowly not fast but never enters the red. I did change the t-stat and what do you mean by bleeeding the coolant and how. If its not the temperature sensor or the fuses(see through fuses are not blown so how do i check the square fuses/relay in the under hood box.

[Rock_28]

Help!!!!!!!!!!

[BNaylor]

Rich asked you whether the fans are turning on when the A/C is turned on. So try that.

You can split the baby by doing the following to get the fans to turn on or what circuit the problem may be in. Disconnect the electrical connector to the engine coolant temperature sensor (ECT). Make sure engine is off first. Then start engine. Both fans should turn on within 5 seconds of starting the engine. There are 3 cooling fan relays in the engine compartment fuse box. The fan relays are controlled by the PCM module via input from the ECT sensor.

Any air pockets or air in the cooling system can cause overheating. There should be a bleeder valve on the thermostat housing where you can bleed air out.

[Rock_28]

Originally Posted by bnaylor

Rich asked you whether the fans are turning on when the A/C is turned on. So try that.

You can split the baby by doing the following to get the fans to turn on or what circuit the problem may be in. Disconnect the electrical connector to the engine coolant temperature sensor (ECT). Make sure engine is off first. Then start engine. Both fans should turn on within 5 seconds of starting the engine. There are 3 cooling fan relays in the engine compartment fuse box. The fan relays are controlled by the PCM module via input from the ECT sensor.

Any air pockets or air in the cooling system can cause overheating. There should be a bleeder valve on the thermostat housing where you can bleed air out.

The fans donot come on when i turn the ac on but I did like you said and disconnected the plug from the coolant sensor and the fans did come on. Now today i just changed the coolant sensor so that wasn't the prob. What next and by the way thanx you helped me alot with my manny gasket and plenum changing

[BNaylor]

Originally Posted by Rock_28

The fans donot come on when i turn the ac on but I did like you said and disconnected the plug from the coolant sensor and the fans did come on. Now today i just changed the coolant sensor so that wasn't the prob. What next and by the way thanx you helped me alot with my manny gasket and plenum changing

You're welcome.

Ok, since fans turn on with ECT disconnected that means the input from the ECT is good to the PCM module. Next it shows the output from PCM to the cooling fan relays is good. So you can rule out the ECT and all cooling fan relays plus the fans. The part not working since A/C is not turning on the fans or since not turning on at 220-230 degrees is your PCM module. It is the brain of the operation. Try disconnecting battery negative cable for a few hours and then reconnect to see what it does. This should cause a quasi PCM reset.

Also, make sure you check for no air in the cooling system just to be sure. Try all of that and lets see what happens.

[Rock_28]

Originally Posted by bnaylor

You're welcome.

Ok, since fans turn on with ECT disconnected that means the input from the ECT is good to the PCM module. Next it shows the output from PCM to the cooling fan relays is good. So you can rule out the ECT and all cooling fan relays plus the fans. The part not working since A/C is not turning on the fans or since not turnng on at 220-230 degrees is your PCM module. It is the brain of the operation. Try disconnecting battery negative cable for a few hours and them reconnect to see what it does. This should cause a quasi PCM reset.

Also, make sure you check for no air in the cooling system just to be sure. Try all of that and lets see what happens.

OK i'll try it, don't be surprised if you hear from me again. LOL Thanx bud!

[Rock_28]

Well i did like you said and when i started the car the fans came on for about 10 seconds ans shut off. I drove the car and then let it sit like i was in traffic and the fans never came on. The teperature read 255 before i shut the car down. This is wierd. I know the thermostat works cause when initially the car warms up goes to 230 and then drops to normal temp. but that only happens once of twice. What do I think now, I don't think it reset. Well at least i know the fans work and the temperature sensor is working.

Rock

[BNaylor]

What was the reason for changing the LIM gaskets? Was it just using coolant or overheating before that? When you did the LIM work did you flush out the old coolant, assuming it is Dex-Cool and run the bleeding process? What replacement coolant was used? On the ECT replacement did you use plumber's tape on the threads? Threads are self sealing and no tape should be used. From what I can see if all of the above is OK then it is pointing to a PCM module. I've seen this on other GM 3100/3400 cars.

But to be safe check the PCM reference voltage at the input of the ECT connector to make sure it is there and the output the ECT to the PCM module.

[Rock_28]

Originally Posted by bnaylor

What was the reason for changing the LIM gaskets? Was it just using coolant or overheating before that? When you did the LIM work did you flush out the old coolant, assuming it is Dex-Cool and run the bleeding process? What replacement coolant was used? On the ECT replacement did you use plumber's tape on the threads? Threads are self sealing and no tape should be used. From what I can see if all of the above is OK then it is pointing to a PCM module. I've seen this on other GM 3100/3400 cars.

But to be safe check the PCM reference voltage at the input of the ECT connector to make sure it is there and the output the ECT to the PCM module.

I had a small leak in the LIM thats why I changed those, its wasn't over heating before but wanted to change the gaskets before it started. I did flush out the old and put in new prestone 50/50, new thermostat, no tape on the ect, I bleed out the sytem until just fluid poured out of the 2 bleeders.
When i did what you said about unplugging the ect sensor the fans did work, but when i plugged it back in they didn't work so are you saying its the pcm module and whats the damage usually for that$$