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Engine Overheating

Tiny
AVERYSMOMMY
  • MEMBER
  • 2008 PONTIAC G6
  • 3.5L
  • V6
  • FWD
  • AUTOMATIC
  • 30,000 MILES
Engine would be warm but heat would not blow warm air. Finally would blow warm air but then the engine would overheat. Heater would then blow cool air. No water leaking anywhere. We thought it was the thermostat sticking so we replaced it. Did not fix problem. Was driving car to mechanic and the car ran hot so we pulled over to allow engine to cool. It would not crank. Fan motor is working and there is no water leaking into floorboard. Any ideas? (Motor was replaced abt 2 years ago and has approximately 30,000 miles. Transmission and body have 178,000 miles.)
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Monday, December 7th, 2015 AT 9:40 AM

29 Replies

Tiny
JOHNNYT73
  • MECHANIC
  • 924 POSTS
Are you sure that you burped all the air out of the cooling system?
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Monday, December 7th, 2015 AT 10:00 AM
Tiny
AVERYSMOMMY
  • MEMBER
  • 2 POSTS
Yes, we did that when replacing the thermostat.
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Monday, December 7th, 2015 AT 3:16 PM
Tiny
JOHNNYT73
  • MECHANIC
  • 924 POSTS
Have you tried replacing the cap?
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Wednesday, December 9th, 2015 AT 7:47 PM
Tiny
MYLUVS534
  • MEMBER
  • 1 POST
  • 2008 PONTIAC G6
  • V6
  • FWD
  • AUTOMATIC
  • 127,000 MILES
I just bought the car from a dealership however didnt buy the warranty but I have a 2008 pontiac g6 and not all of the time but my car is over heating up to 220-225 but fans kick on and cool it down im just afraid 225 if too hot and can cause damage
I dont understand it! Please help me?
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,873 POSTS
I too get nervous with temperatures that high, but that's how some models are designed. On a lot of GM cars the fans don't turn on until 220 degrees. That's why we use a pressure cap on the cooling system. Every pound of pressure raises the boiling point by three degrees Fahrenheit. Water boils at 212 degrees, then a 15 pound cap adds 45 degrees to that, so you're safe as long as there's no leaks in the cooling system.

The important point is you observed the radiator fan does turn on.
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
JOYMARTIN1966
  • MEMBER
  • 1 POST
  • 2008 PONTIAC G6
  • 3.5L
  • V6
  • 92,000 MILES
My car is overheating. Yesterday we ran it and it started running hot, we sat on side of the road until it cooled down then I decided to turn around and go home, about 5 miles up the road it Never ran hot. So we decided to press our luck and drive it own to town 20 miles away and it never ran hot again, there or back. That night my son went to work again 20 miles away and the same thing happened it ran hot he sat awhile and went on to work, The next morning same thing happened, so we decided to change the thermostat and now it seems to be worst it will not run 1/3 of a mile before it gets hot. Can you give me any advice?
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,873 POSTS
You may have a radiator fan that is intermittently not turning on. You didn't say at what speeds this is occurring. The radiator fan isn't needed at highway speeds.

The next suspect would probably be a leaking cylinder head gasket. That will allow combustion gases to pool under the thermostat and prevent it from opening. Thermostats have to be hit with hot liquid. Hot air won't do it. Your mechanic can perform a chemical test at the reservoir for that.
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
ED LEESON
  • MEMBER
  • 1 POST
  • 2008 PONTIAC G6
Engine Cooling problem
2008 Pontiac G6 6 cyl Front Wheel Drive Automatic

will this product hurt my cooling systeme I have a small leak in the rad
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
FACTORYJACK
  • MECHANIC
  • 4,159 POSTS
It should not hurt it, however I personally do not endorse the use of them products. Then again, I have to work on the vehicles after that stuff is in the system. Is there another alternative? Was the leak self inflicted, or is the manufacturer warranty expired?
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
DAJEWOO
  • MEMBER
  • 2 POSTS
  • 2007 PONTIAC G6
  • 91,000 MILES
3.5 liter engine. My car overheats as I drive it, and the heater does not get warm. It is winter here about thirty six degrees and it overheated after driving in less than five minutes. Sometimes if your on the highway for a long stretch the heater will get warm but if you slow down it cools. Also, noticed the fan seems to stay on a long time after you stop the engine. We replaced the thermostat, added coolant, and there does not seem to be any leaks, although I am not sure the water is circulating. Any help on what might be wrong would be greatly appreciated.
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,873 POSTS
You are right about lack of circulation. The clue is you will find the upper radiator hose near the engine is hot but there is no hot coolant circulating into the heater in the dash. If the system was low, including after replacing the thermostat, there is likely an air pocket that has to be bled out. Look for a bleeder screw near the thermostat housing. If there is not one, look for a sensor near the thermostat that can be removed to burp the air out. Thermostats only open in response to hot liquid, not hot air, so an air pocket will prevent it from opening and cause overheating.

If you bleed out a lot of air but the problem comes back in a few days, suspect a leaking head gasket as the most likely cause. It will continue to allow air into the coolant and coolant will go out the exhaust. There are two different tests your mechanic can perform to identify a leaking head gasket.
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
DAJEWOO
  • MEMBER
  • 2 POSTS
Could not find a bleeder valve or sensor to take off. It is pretty crowded, but took off each radiator hose and filled with coolant. Seemed to remove the air and now is working great again. Thanks for the advice, it helped put me on the right track.
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,873 POSTS
Great news. Cannot argue with success. Keep an eye on the coolant level in the reservoir. If it starts going down, you can add a bottle of dye to the coolant, drive the car until the level goes down some more, then search with a black light. The dye will show up as a bright yellow stain that you can follow back to the source. If you find it inside the tail pipe, suspect a leaking head gasket.

Your mechanic can also perform a "sniffer" test. That involves drawing air from the radiator through a glass cylinder with two chambers partially filled with a special dark blue liquid. If combustion gases are present, that liquid will turn bright yellow. Combustion gases get forced through a leaking head gasket, or less commonly through a crack in the head, and cause that air pocket by the thermostat, and when the engine is off and cools down, coolant is drawn into that cylinder and forced out the tail pipe later. Coolant can also be sucked into the cylinder while the engine is running.
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
KSMITH810
  • MEMBER
  • 6 POSTS
  • 2007 PONTIAC G6
  • 3.5L
  • V6
  • FWD
  • AUTOMATIC
  • 106,000 MILES
I was driving my mom to work on the freeway, ran over a saftycone bottom side hit first broke my radiator, tried driving it home and kept putting water into the reservoir replaced the radiater, the car still was overheating replaced the thermostat tested the old 1 didnt work. Still overheating we just replaced the o ring in the metal heater line to the upper radiator hose housing still overheating noticed by the o ring the metal hose is leaking air still but not misting out coolant.I am hoping if I replace the metal pipe and it still overheats what should I b looking at to fix this I have no heat blowing inside the car and its winter, I have 2 kids I am doing the work myself cause I cant offord to take it to a mechanic, if anyone can help much appreciated. Thank you
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
What engine does it have?
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
KSMITH810
  • MEMBER
  • 6 POSTS
3.5l v6
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
KSMITH810
  • MEMBER
  • 6 POSTS
And now I have fixed the air leak out of metal pipe and now I noticed new oil on the engine under the distributor cap could that be part of the head gasket and if it is than obviously I would have to replace it, but what els would I need to take off and is there more gaskets I would have to replace?
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
The first thing to resolve is to get all the leaks fixed and air pockets out of the cooling system and that may not be easy. Pressure test the cooling system to determine if you have any leaks. Once you confirm all the leaks are fixed, then I would have the system vacuum filled to remove all the air. At this point I wouldn't be surprised if the previous overheating hasn't caused internal damage like a blown head gasket.
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
KSMITH810
  • MEMBER
  • 6 POSTS
No check engine light on eather
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)
Tiny
TIMRISS
  • MEMBER
  • 2 POSTS
  • 2005 PONTIAC G6
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 57,000 MILES
While cleaning my car the other day, I decided to add some coolant to my engine. This has been the second time in the two years I've owned the car my low coolant light has went on. Well I added the coolant and later that night my temperature gage starting steadily rising and stopped at 200 degrees in the middle of the night. This is very alarming because before I added any coolant my temperature gage would barely rise at night. I got in my car the following afternoon and again it stopped at 200 degrees. This is the first time ive seen it that hot at any time of day. My car has not overheated yet and overheats at 260 degrees. I am very concerned and plan on visiting a mechanic soon but I cant get there for a few days. Has anyone else ever had a problem like this where your car actually gets hotter after adding coolant? I looked in the manual and my car said to use dex-cool. I used Predstone 50/50 antifreeze which is the same exact stuff I used last time I filled my coolant and I didnt have this problem. Can anyone help?
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Wednesday, August 7th, 2019 AT 5:11 PM (Merged)

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