Question about 2005 GMC Sierra

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2005 GMC Sierra Overheating

I'm having a problem with this truck overheating. The truck is a 2005 GMC Sierra 1500 2 WD 5.3L V-8. So far we replaced the the water pump and the thermostat but the truck still overheats quickly. Also, when we run the heater it does not blow hot air but the gauge is running 230-260. I've noticed other people having similar issues...any help would be most appreciated..

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  • Irene allard Feb 05, 2009

    If you are asking if I've changed the coolant...than, yes I've drained and replaced all the coolant. As far as I can see there are no leaks. FYI: When the car was idling for 1/2 hour it ran without any temperature issues--thought the issue was taken care of BUT as so as I drove it, about 1 mile, the truck overheated.

  • Irene allard Feb 05, 2009

    When the pickup starts to overheat the heater starts to blow cold air--I'm not sure what is causing this. If someone would talk me thru how to bleed the air off of the coolant system, I'll give that a try. Thanks.

  • Anonymous Feb 12, 2009

    I have the same problem. It's a 2004 GMC Sierra 1500 Crew cab. 5.3L
    Was the problem air in the system or was it the head gasket?

  • James Bradburn
    James Bradburn May 11, 2010

    is there a small bleeder bolt on the thermastat housing? Is there a bleeder bolt anywhere on the top hard coolent lines? If so crank the car turn the bolt till coolent or air comes out. But let the truck warm up some first. When there is a stream of coolent coming out and no air then its good. But being that there is no heat then it may take a min. Let me know how you doing on that.

  • James Bradburn
    James Bradburn May 11, 2010

    Ok but you changed the coolent but will need to bleed the coolant system to get all air out of it.

  • James Bradburn
    James Bradburn May 11, 2010

    Have you bleed the cooling system?

  • Frankie Klassen Sep 01, 2012

    I also have the same problem on my 04 Sierra 1500 Crew cab 5.3L, Did anyone figure out what caused this?

  • Anonymous Mar 21, 2014

    How do I replace the fuel pump on my 1998 Sierra GMC truck?



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  • Expert
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If your sure there is no trapped air in system after refill and air bleed off, is fan clutch pulling good air thru radiator? Even if it is, the heater should have coolant as hot as what temp gage is showing! Try backwards flushing heater core (dex cool is notorious for plugging these up). There is a TSB for cracked cylinder heads from GM for unexplained coolant loss.Remove drivers side valve cover, and look at center three head bolts for coolant around them, if coolant has been getting in thru this suspect area, there will be a milky/pudding like goo under valve cover and on head. GM had a company called Castec cast these and the areas near the head bolts were found to be too porous (NO recall YET!) Ya, you guessed it, replace heads! Unfortunately, if its gotten hot to many times, it has probably hurt the heads/gaskets. Hope this helps. PS: The castec logo is under the rearmost pair of rocker arms,may have to remove them to see.

Posted on Feb 05, 2009

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  • GMC Master
  • 443 Answers

Hate to ask but did you put the thermostat in rightside up ? and someone else might be right did you bleed the system and get the air out of it? sometimes there is a air lock that will drive you crazy.. another thing when you replaced the water pump did it heat up before you changed it ?? if so did you put right gaskets on it for correct flow.. ? thanks Jerry if you have more holler

Posted on Feb 05, 2009


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