radiator fan problem

[Mr Crow]

I'm putting the thermostat in today. Is there any special way to put the antifreeze in? Do I have to bleed the system?

[Mr Crow]

Installed the thermostat. No change. Unplug harness to sensor, fans go on. Plug it in, they go off. Could it be that the new temp sensor is defective? I have seen it happen.

[BillBoost37]

Crow...

Normal t stat temp is 195F. Therefore you should usually see 200F on the gauge. Fans don't turn on til 214-218, for low speed.

What you describe is perfect operation and the fans running when unplugged is s failsafe for the system with a short or open wire.

Now..if' you'd like some more help. How's about you tell us what you are driving, if you have mods and if your temp gauge matches what the pcm sees the temp to be.

[Mr Crow]

BB37 Sure. It's a 1998 Grand Prix GT. 3800 Gen II. No mods. So I take it that the gauge should go to 200 degrees before the fans go on? We just bought the car 2 months ago. Should the fans run when the key is off? As I said, I'm unfamiliar with the newer stuff. I have a 71 Torino wagon and a 65 Chevy Van. Newest is an 89 S-10 pickup. The GrandPrix is very cool. I've always liked that body style. Thanks, Crow.

[Mr Crow]

Obviously I have a lot to learn about this car. The car runs steady at 200-210 degrees now. The gauge must have been reading incorrectly. Drove it around for about 50 miles and never overheated. Also, had a noise I thought was an alternator bearing going bad. Removed the belt and saw that the idler pulley was missing. That's right,Gone. Only the bearing was there. and that was locking up and turning purple. Put a new pulley and belt on and all in good again. Love this car.