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2007 1SG STS v8 awd
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502 Posts
Discussion Starter #1
Why when running the a.c. And sitting still the engine temp rises then it shuts the ac off because the engine is hot. This never happened before. Only while sitting for a while it rises. If I increase three rpms a but it helps to keep the temp down also.
 

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2006 STS V8 1SF RWD
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6,486 Posts
Mine did this yesterday too, granted it was 90 degrees out but I'm thinking it's the thermostat not operating correctly. Once I got going down the freeway it dropped down to normal temp almost immediately. Curious to see where this one goes...
 

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'06STSV(sold), '13 SHO
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616 Posts
Increasing rpm increases flow so you are moving coolant thru the radiator faster gaining some cooling just by moving more fluid. The issue you need to figure out is why if it not cooling enough at idle.

Possibly a failing water pump, failing cooling fans, thermostat, clogged water jacket in block, clogged radiator core.

What sort of temp is it running when you cruise on freeway or even side roads, does temp drop as soon as you are moving at all? That points to radiator (and my initial gut call) working well as it responds to airflow. If that is the case I would look at cooling fans, see if they are running properly and fast enough. They are there for when the car is not moving which is when you are having issues, best radiator in the world can't do Jack S if there is no air moving thru it....
Clogged radiator could show similar symptoms though usually not get fully cooled even when moving. Failing pump/therm also will not show big change in moving vs not moving, so check that 1st would be my recommendation. If needle goes from hot to normal just by having the car moving then I would look at fans #1.
 

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2006 STS V8 AWD, '95 Ford Ranger
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29,016 Posts
The car is designed to cool properly at 100MPH on a 100F day with a 100MPH following wind.

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Check for the radiator airflow being restricted by bugs or leaves. Check that the air deflector underneath in front hasn't been destroyed by driving up on the curb.
 

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2007 1SG STS v8 awd
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502 Posts
Discussion Starter #5
While cruising or just moving period the temp immediately drops. I just changed water pump two years ago and it did the same thing, ran hot until I moved. I suspect the two electric fans because they haven't come on at all. When the water pump was bad all the coolant leaked out and the fans would come on before it got hot. How could I check this for sure. Fans worked last year when ac was running when it was 90+ outside. Where is the fuse and what is it labeled so I could check that. And what else could cause both fans to fail. The clutch fan works of course it turns as the engine turns
 

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'06STSV(sold), '13 SHO
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616 Posts
I suspect the two electric fans because they haven't come on at all.
^^^^^^ You have your answer. If the car gets hot enough it disables the AC and the fans are not running then you have bad fans, fan relay or control module for them. I do not know the details of the STS fan circuit enough to help more than knowing it is something in the circuit that is bad if the fans are not running...
 

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08 STS4 V8 1SG & 04 SRX4 V8 & 01 Monte SS
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5,012 Posts
Does anyone here have the heavy duty cooling package?
(Should be pretty obvious with the big mechanical fan on the front of the motor).

If you do perhaps the mechanical fan is failing and not spinning correctly, or one of the pair of electric fans are having issues.
Or in the water pump category the HD cooling cars have a standard pump and an auxiliary pump as well, perhaps one has failed?
My 1SG hasn't had a temp other than 1 notch below midway on the gauge once the car is 'warmed up'. Doesn't matter what I'm doing it never goes up past that point.
 

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2007 1SG STS v8 awd
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502 Posts
Discussion Starter #8
Ludacrisvp said:
Does anyone here have the heavy duty cooling package? (Should be pretty obvious with the big mechanical fan on the front of the motor). If you do perhaps the mechanical fan is failing and not spinning correctly, or one of the pair of electric fans are having issues. Or in the water pump category the HD cooling cars have a standard pump and an auxiliary pump as well, perhaps one has failed? My 1SG hasn't had a temp other than 1 notch below midway on the gauge once the car is 'warmed up'. Doesn't matter what I'm doing it never goes up past that point.
I have the heavy duty cooling package
 

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2005 STS4
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30 Posts
Like Luda on my 1SG....

Have you checked the radiator fan relays (low and Hi speed $5) located under the hood? You can swap them out with other relays that are the same.

Other than that my money would be on the temperature sender/sensor ($15). I do not think the thermostat is stuck since the fans are never kicking on.
 

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2006 STS 1SG & 2007 STS 1SE
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2 Posts
I've got the HD cooling, too. No troubles. Once about 4 years back, I did have to replace the aux coolant pump under warranty. It was leaking. No trouble since.
 

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2016 XTS FWD Platinum
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1,107 Posts
I had a similar problem with my 06 STS also with the HD cooling package. I remember last summer, I had the car running probably for about 15-20 minutes & everything was good. Then I heard some strange noise, I can't really even remember what it sounded like, and then I noticed the temperature gauge start to go up past the halfway point. It had NEVER done that before. It always stayed right below the halfway point no matter what the load on it was. I immediately turned it off to let it cool off. I restarted it probably an hour later & everything seemed fine. Granted, it was the middle of the summer & it was probably 105 degrees outside. As long as I was driving the vehicle, everything seemed ok but as soon as I was idling for any extended time, the temperature would heat up. I took it in to have the cooling system checked out but they couldn't find anything wrong. Everything was fine all winter but at the beginning of this summer, it started to do the same thing. I had it checked again but they couldn't find anything wrong. I ended up trading it off before I could figure out what was wrong.

I'm curious to find out if anyone else figures out what it could be.

Max
 
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