Radiator fan won't activate? [Archive] - Glock Talk

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pellertpale
04-23-2007, 17:57
My '98 Pontiac GP GT stays in the proper temo. range on the interstate, but as son as I slow down it gets up to 220-230. I haven't heard the fan kick on either.

What are the possible problems? A sensor, or the FAN itself? I don't know a whole lot about fixing cars, if that's not obvious.

Any advice will be appreciated.

NotAMonte86
04-23-2007, 19:03
Not sure at what temp the fan is supposed to kick on... I know on one of my GM's it was too high for comfort, so I wired up a switch to the fan.
But if you're sure it's over the kick-on temp, then there are a couple things it could be. Turn on the a/c... which should turn on the fan. If the fan kicks on, then you may need to replace your temp sensor. If the fan doesn't come on, then it could be the fan motor or relay. In that case, swap relays with a known good one and check again.

SBM
04-23-2007, 19:43
Originally posted by pellertpale
My '98 Pontiac GP GT stays in the proper temo. range on the interstate, but as son as I slow down it gets up to 220-230. I haven't heard the fan kick on either.

What are the possible problems? A sensor, or the FAN itself? I don't know a whole lot about fixing cars, if that's not obvious.

Any advice will be appreciated.


All GM vehicles are known for a high temp to activate the fan (s).

As suggested, turn the AC on, or defrost..either, and see if the fan starts. If it does, you have removed the fan itself from the problem.
If it does not start, they are cheap and simple to replace...but you need to verify that you have 12VAC to the motor on the harness when it should be.

If it DOES start with the AC on, you have either

A bad sending unit for the fan.
A bad temp sender, and its showing higher than normal...and you havent given the fan time to start...even though the dash is reading high.

Also, keep in mind that some of the newer GM vehicles started having the fans controlled by the PCM. I dont have a wiring diagram for that model here...but IIRC that one does, particularly if its the HO V6. I quit working for GM about 99...so my memory on those is shakey but Im sure that one has a fan temp sensor, that feeds to the PCM that turns the fans on...its also cheap IIRC...about $30 or less.
Ask me about an F body tho...and Ill tell you that you NEVER want to replace the sending unit for the fans on a V8....Id like to shoot the idiot that thought under the passenger side exhaust manifold was a good idea.

pellertpale
04-24-2007, 14:39
Will try the AC in a few minutes. I have replaced other coolant/air circulation parts a while back. Damn GM! Never again will I spend my money on their crap.

pellertpale
04-24-2007, 15:38
So my fan activated, but (you guys are probably going to kill me) my radiator hose is not solid. It is squeezed together oblong oval style flat side on top and bottom. Do I need coolant/water? If so what temp do I wait for it to cool to before I add it? Shouldn't the hose be stiff with water/coolant?

SBM
04-24-2007, 20:36
Originally posted by pellertpale
So my fan activated, but (you guys are probably going to kill me) my radiator hose is not solid. It is squeezed together oblong oval style flat side on top and bottom. Do I need coolant/water? If so what temp do I wait for it to cool to before I add it? Shouldn't the hose be stiff with water/coolant?

Well...

Is it the top, or bottom hose? If its the bottom, replace it with a new hose, and insure that the new hose has a spring in it. They tend to rust out over time, get removed by someone that does not understand why they are there...get sold without the spring, etc, and try again. While you have the system empty, replace the coolant, and replace it with the proper solution ratio, remembering that it also acts as your water pump lube.
If its sucked shut, its possible that you have also, the wrong thermostat in the car...but not as likely as simply a bad hose.

The bottom hose is the "intake" as it were, and they are under pretty good suction when the engine RPMs are up there.
There were at least 4 service bulletins that we saw about this, and how some of the aftermarket hoses didnt have the spring.
Replace the hose, refill the coolant, insuring you get all the air out of the system, and, then, simply allow the car to idle watching the temp. You can also remove the rad cap, and insert a thermometer into the coolant, and watch when the fans kick on, if they do. GM vehicles that year will vary, but most fans will kick in between 220F and 245F.
It seems high, but it was done for emission controls during that time frame. My '92 Firebird will not come on till about 240. Its normal, and ok.
If its still not cutting the fans on over that, then its time for a new sender.

pellertpale
04-29-2007, 06:58
So I took the cap off the other day, and found what looked to be peanut butter. I took my car to the closest Jiffy Lube, and they did a flush and fill. Apparently the last placed I took it for an oil change topped off my coolant with normal fluid not dex-cool. i was very angry to hear this. I know it was from the garage(a napa certified establishment) I took it to due to the time frame.

The thing that really got me was the kid mopping the floor at jiffy lube knew not to mix the two, but the napa guys...

well anyway I will keep you posted.

Thank you for your time!

Bushflyr
05-04-2007, 12:09
You should really consider going green on your coolant. Dex-cool causes no end of trouble. Just drain it flush a couple times and fill with green. Your motor will thank you. :wavey: