2000 Saturn SL2 2000 Saturn SL2 cooling fan only coming on

2000 SATURN SL2
115,000 MILES • 4 CYL • FWD • AUTOMATIC
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TONER
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I have a 2000 Saturn SL2 and recently in stop and go traffic we saw steam coming from under the passenger side of the hood and saw it coming from the coolant cap on the expansion tank and the temp gauge was about halfway (it is ALWAYS at 1/4 when driving/stopped).

I changed the bottle and cap with new OEM parts, still having the same problem, so I changed the Thermostat and temp sensor (brass tipped) and the temp gauge is still going up. I also swapped the relay with the horn relay since they are the same # and the horn still works using the fan relay.

The cooling fan only comes on with the AC on, when switched off the fan turns off. I haven't let it go above 1/2 way on the temp gauge since I am afraid to do so. For the 6 years I have owned this vehicle the gauge has NEVER gone over 1/4, even when I lived in AZ for 3 years.

I have never noticed/heard the fan before since everything has been working, but when the temp gets past 1/4 and I turn the AC on the temp gauge goes down, so there must be a fan issue.

The only 2 other things I can think of are the PCM or the fan motor itself, but it works with the AC on!

Thanks in advance for any help!
Aug 29, 2010 at 7:26 PM
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SATURNTECH9
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Let the car idle and see if the fan come's on just past half way on the gauge that's where the fan should come on in that yr and model.You probably had a bad temp senor and that's why it boiled over because the coolant temp was really much hotter then half way on the gauge.If you had a good cap before you changed it it shouldn't have boiled over till the gauge read into the red.Just over half way on the gauge is 222-226 degree's that's when the fan come's on in that yr and model saturn S model.Let me know what you find.
Jan 12, 2019 at 12:26 PM
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TONER
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ok, I will test it further in the morning and post back, it's just NEVER gone above 1/4 on the temp gauge, I don't understand. thanks!
Jan 12, 2019 at 12:26 PM
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SATURNTECH9
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If your car never got above 1/4 on the gauge you had a problem with your thermostat sticking open.When the car sits and idle's the gauge will rise to just above 1/2 way then the fan come's on.I'm glad you changed the thermostat sound's like you really needed a new one.
Jan 12, 2019 at 12:27 PM
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TONER
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Everything is working. The fan comes on about a 1/5 of the way between the 1/2 and 3/4 marks, and the fan goes off once it drops below the halfway mark. Sitting in the driveway after the fan goes off a few minutes later the gauge goes back up and the fan comes back on.

So as of right now, a new thermostat, temp sensor and a new cap and everything is working.

Just have to get used to the temp gauge being around 1/2 now (the right reading) since you said it was around 1/4 due to a stuck thermostat.

So I'm thinking the stuck thermostat must have also got stuck closed, restricting coolant flow, for the vehicle to lose coolant out of the cap? When the vehicle originally did this, I replaced the bottle and cap, then it did it again, that's when I changed the thermostat, temp sensor and cap (again). Unless the temp sensor was also bad, but the gauge did work. Just trying to understand what caused the overheating/coolant loss. The coolant level when cold has always been correct (check my vehicles every week especially when I was living in AZ).

Thanks for the help!!!
Jan 12, 2019 at 12:27 PM
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SATURNTECH9
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I have never seen a thermostat stick closed they always stick open that's why the car stayed at a 1/4 on the temp gauge.Most of the time what cause's the car's to over heat is the coolant temp sensor.So my guess is the coolant temp sensor caused the boil over.Sounds like everything is working great now glad to hear it.
Jan 12, 2019 at 12:27 PM