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Posted on Dec 24, 2010

I have a 2005 pontiac montana and i am having trouble with it over heating, i have changed the water pump, thermostat, heat sending unit, drained and flushed the radiator and purged the air out of the system from the discharge side of the pump and the return side just before the radiator and it is still over heating any suggestings??

  • Sean  Piquet
    Sean Piquet Dec 24, 2010

    1. Have you checked to ensure your electric radiator fan is kicking in once the coolant temperature has reached the threshold temp level? If the temp sensor has failed or the fan motor has died you will have no fan and there will be insufficient air flow through the radiator in some driving conditions.
    ------------------------

    2. If the fan is OK then I suspect either: ............
    ---- there is a debris blockage in the cooling system in the engine impairing coolant flow; or .........
    ------ you have an air lock in the cooling system impairing coolant flow from inadequate bleeding of air.

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  • Posted on Feb 02, 2011
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Sean I have a 2004 Montana and mine is also overheating. I just paid Pep Boys $300 to replace thermostat and it is still overheating. They checked for coolant leaks, water pump is okay, the pressure checked out ok. No air in the system, etc. Today I brought it to a different mechanic and he says my cooling fan is kicking in very slow after the temp gauge goes 3/4 up which is not supposed to happen. My fan does not have a relay and he said it is either the temperature sending unit, but most likely it is the COMPUTER which is going to a very, very expensive repair. He said this happens a lot with Montanas! I am pissed. I just bought it used and the previous owner probably dumped it b/c he knew it needed a computer. Also the Fuel gage does not work and it will cost $800 to replace the fuel tank which contains the fuel sensor.

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