09 3.5L GT Overheating Nightmare - Pontiac G6 Forum
 
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post #1 of 6 (permalink) Old 08-13-2018, 01:01 AM Thread Starter
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09 3.5L GT Overheating Nightmare

First let me start off by saying that I hate, hate, HATE this vehicle. I'm a Jeep guy and always will be. That being said my mother purchased this car in 2010 with 20K on it and used it as her daily for about 6 years and in those 6 years. She didn't really keep up with her maintenance & ran this thing hard for those 6 years (I basically had to beg for her to take it to get it's oil changed everytime it needed it). It's had a rough life and it's now been sitting with this issue for 2 years because every time it's supposedly 'fixed' it comes right back & it's been nothing but issues hence why i've grown to despise this vehicle. We've taken it to professional mechanics (at least 3 different shops) to have them try and fix it's overheating issue and every time we get the call saying "you're all fixed up" we go a few days and lo and behold it overheats again. In the past 2 years we've gone through 4 thermostats, 2 water pumps, 1 radiator, 2 heater cores, a switch from dex-cool to standard coolant and this f****r is still overheating. The problem comes and goes as well. After completing my 2nd heater core replacement yesterday I took it for a 20 minute cruise around town, got up to 100mph on the highway A/C blasting on full to try and put the engine under max load and it maintained a cool 200* the whole time and I thought I fixed it. My brother (who is receiving the vehicle as a hand-me down) called me today and said the temperature gauge spiked for a few minutes and then went back down to 220. My suspicions are starting to lead me toward a faulty radiator fan or fan circuit because I don't know what else It could be aside from air in the system but I had the bleeder valve opened for 15 minutes while it ran and I manually pumped the hose's to try and burp the air out. I'm at a loss here and any help would be appreciated!

Thanks!
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post #2 of 6 (permalink) Old 08-13-2018, 09:18 PM
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Originally Posted by Skippy102595 View Post
First let me start off by saying that I hate, hate, HATE this vehicle. I'm a Jeep guy and always will be. That being said my mother purchased this car in 2010 with 20K on it and used it as her daily for about 6 years and in those 6 years. She didn't really keep up with her maintenance & ran this thing hard for those 6 years (I basically had to beg for her to take it to get it's oil changed everytime it needed it). It's had a rough life and it's now been sitting with this issue for 2 years because every time it's supposedly 'fixed' it comes right back & it's been nothing but issues hence why i've grown to despise this vehicle. We've taken it to professional mechanics (at least 3 different shops) to have them try and fix it's overheating issue and every time we get the call saying "you're all fixed up" we go a few days and lo and behold it overheats again. In the past 2 years we've gone through 4 thermostats, 2 water pumps, 1 radiator, 2 heater cores, a switch from dex-cool to standard coolant and this f****r is still overheating. The problem comes and goes as well. After completing my 2nd heater core replacement yesterday I took it for a 20 minute cruise around town, got up to 100mph on the highway A/C blasting on full to try and put the engine under max load and it maintained a cool 200* the whole time and I thought I fixed it. My brother (who is receiving the vehicle as a hand-me down) called me today and said the temperature gauge spiked for a few minutes and then went back down to 220. My suspicions are starting to lead me toward a faulty radiator fan or fan circuit because I don't know what else It could be aside from air in the system but I had the bleeder valve opened for 15 minutes while it ran and I manually pumped the hose's to try and burp the air out. I'm at a loss here and any help would be appreciated!

Thanks!
There are two cooling fans controlled by three relays. The relays allow the fans to be 0) turned off, 1) wired in series for low, 2) wired such that one is off and the other on full, for medium, 3) and both on for high. The engine computer controls the three relays.

If one of the relays is bad, when the engine commands the fans to go from low to medium (or medium to high), the fans may instead go from low to off (or medium to low). Don't hold me to all those possible combos, but understand, the fans may not step up like they're supposed to. With one intermittent relay, the fans will work correctly at some times, and not at others.

On the highway, enough air usually gets pushed into the radiator for this to go unnoticed, but around town, when stopped in traffic is when you'll notice it.

I don't know for sure if I can diagnose it down to one relay. But you can replace all three for about 30 bucks, a little less via mail order. In the underhood fuse block, these are labeled 28, 29 and 30.

HTH.

Doug

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post #3 of 6 (permalink) Old 08-15-2018, 03:35 AM Thread Starter
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Thank you for the reply Doug. I tested all 3 fan relays yesterday and they all clicked when hit with 12v power so I’m not sure if they are the problem (could still be worth a try for $30).
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post #4 of 6 (permalink) Old 08-15-2018, 06:53 AM
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Thank you for the reply Doug. I tested all 3 fan relays yesterday and they all clicked when hit with 12v power so Iím not sure if they are the problem (could still be worth a try for $30).
It's the contacts that can go bad. They may click, but not necessarily close the circuit.

And some times they do work, which makes them harder to diagnose.

HTH.

Doug

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post #5 of 6 (permalink) Old 08-16-2018, 01:35 AM
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They are easy, pull them out and test as shown here. Having worked at a radiator shop rebuilding radiators and doing coolant leaks sounds like one of two things either that dex-cool which is some nasty crap can build up inside the radiator, engine ect and even though parts were replaced if you dont blow all that crap out it just gets right into the new components clogging them up. Or you got a cracked head. You cant know if the head is cracked without pulling them off and use some dye and a black light to know for sure. What you can do to blow out your system is remove the t-stat, put the elbow back on, run the car with the upper radiator hose disconnected from the radiator and blow compressed air and water through it, you will need this to do that which you will have to make your self. You get the idea.
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post #6 of 6 (permalink) Old 08-16-2018, 07:17 AM
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out of curiosity, have you changed out your coolant temp sensor?

2007 PONTIAC G6 GT

Waterfowler's 6 <---- Check out my 6

Last edited by waterfowler76; 08-16-2018 at 07:22 AM.
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