Overheats at idle

ALEX&ALICIA

MEMBER
2005 CHEVROLET EQUINOX
4.6L
V6
4WD
AUTOMATIC
130,000 MILES

Okay, my fiancé and I have been battling this for over a year it does fine in town driving as long as you do not drive for over half and hour as soon as you do and come to a stop the temperature gauge stars skyrocketing every time. We have gone to many mechanics and have replaced water pump, radiator, overflow cap, and yes the fans work at both speeds. We do bleed the air out but still after driving for a while it over heats and I am not sure if all the air ever gets out. It is getting really frustrating and we do not know what to do. There is no anti freeze in the oil and the exhaust does not blow clouds of white smoke. Please help! Oh ya and sometimes when the engine is over heating the radiator is cold as can be but I have felt the radiator and burnt myself also. If we rev the engine while it is over heating it cools down. Also, had Midas do a pressure test on it and said it was fine, supposedly did a whole diagnostic and told me it was water pump which I replace before the radiator.

2 Replies

CARADIODOC

MECHANIC
33,871 POSTS

Thank you for listing the engine size and mileage. We need the engine size when looking up wiring diagrams and parts lists which can be quite different, and we look at the mileage when making judgments as to the best suspects.

One thing you might consider is having a chemical test performed at the radiator, or for GM vehicles with no radiator cap, at the reservoir. This is to check for a leaking cylinder head gasket. The test involves drawing air, while the engine is running, through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are present the liquid will turn bright yellow.

Those gases that sneak into the cooling system can pool under the thermostat and prevent it from opening. Thermostats have to be hit with hot liquid to open. Hot air will not do it. One potential clue to this is if you repeatedly bleed the system and keep finding air.

If you find a head gasket is leaking and it remains a minor leak, consider drilling a very small hole in the plate of the thermostat. A lot of engines come with that already. That will let the air pass to the radiator and reservoir, then the hot liquid will get to the thermostat.