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no heat + truck is running hot

This is a discussion on no heat + truck is running hot within the Technical / Maintenance forums, part of the General Discussion category; I have changed the thermostat and flushed the heater core, the truck will warm up just fine but it will ...

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    no heat + truck is running hot


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    I have changed the thermostat and flushed the heater core,
    the truck will warm up just fine but it will not blow any heat, when i go to drive it, it quickly goes up to 240 degrees and then sometimes goes down, but it never blows warm air.
    i just cant figure out what it could be?
    somebody please help I am at my parents house 3 hours from home and need to get back sunday

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    Hey watch this Colby 04's Avatar
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    Re: no heat + truck is running hot

    pull the thermostat, see what it does. did it overheat before the new thermostat?

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    Re: no heat + truck is running hot

    changed the thermostat this morning, it was doing it yesterday before I changed it, i had the water pump and a head gasket replaced a couple weeks ago and havent had any problems until now, i really am starting to think that there is a air pocket trapped in the heater core, but would that cause my truck to run extremely hot?

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    Hey watch this Colby 04's Avatar
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    Re: no heat + truck is running hot

    Quote Originally Posted by blacktavert
    changed the thermostat this morning, it was doing it yesterday before I changed it, i had the water pump and a head gasket replaced a couple weeks ago and havent had any problems until now, i really am starting to think that there is a air pocket trapped in the heater core, but would that cause my truck to run extremely hot?
    the heater core is located under the dash and wouldn't cause your truck to overheat(unless it's leaking), but will contribute to lack of warm air. I would try pulling the thermostat to see if it will have any effect on it.

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    Re: no heat + truck is running hot

    agreed check the passanger side floor for any wetness, if so the heatercore is leaking.

    Also check where the heatercore comes through the firewall for a hose leak
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    01 GMC Z71 SUNSET ORANGE DRTRAYDEUCE's Avatar
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    Re: no heat + truck is running hot

    no heat + hot motor = no water , that has been my experience .

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    Re: no heat + truck is running hot

    The heater core is the highest point on these trucks, therefore they are notorious for trapping air pockets. Pull the heater hose on the return side and run the truck and see if if pushes alot of air out.
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    Re: no heat + truck is running hot

    Quote Originally Posted by Sinister Z71
    The heater core is the highest point on these trucks, therefore they are notorious for trapping air pockets. Pull the heater hose on the return side and run the truck and see if if pushes alot of air out.
    this is the problem im sure. anytime u flush your rad watch ur temp 1 air pocket do alot of damage
    84 shortbox on 20s blown 383stroker

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    Re: no heat + truck is running hot

    i have changed the thermostat, and I have no leaking on the floormats, I have a feeling it is an air pocket, i just could not get it out,
    i end up taking it in

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    Re: no heat + truck is running hot

    Quote Originally Posted by blacktavert
    i have changed the thermostat, and I have no leaking on the floormats, I have a feeling it is an air pocket, i just could not get it out,
    i end up taking it in
    Dude just pull the return line from the heater and let it push the air out and reattach hose, bleed as necessary.
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    Custom true duals with 40 series Flow masters and 4" x 24" Stainless angle cut tips angled out at the bed corners.

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    Re: no heat + truck is running hot

    Mine is doing the same thing his is doing But mine is leaking when I had my AC on this summer it leaked by the passenger side is this my heater core? And now my heat is not blowing hot... What should I do to solve this problem

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    Re: no heat + truck is running hot

    Quote Originally Posted by 98RhinoZ71
    Mine is doing the same thing his is doing But mine is leaking when I had my AC on this summer it leaked by the passenger side is this my heater core? And now my heat is not blowing hot... What should I do to solve this problem
    replace heater core...and bleed system for air pockets..

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    Re: no heat + truck is running hot

    Quote Originally Posted by 98RhinoZ71
    Mine is doing the same thing his is doing But mine is leaking when I had my AC on this summer it leaked by the passenger side is this my heater core? And now my heat is not blowing hot... What should I do to solve this problem
    Sounds like it is time for a new heater core

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    Re: no heat + truck is running hot

    I've always heard that if you have air pockets that won't come out, put the front of the truck on ramps, effectively making the rad cap the highest point in the system.

    Never had the problem, so I never tried it... still thought it could help.
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    Re: no heat + truck is running hot

    How hard is it to install a heater core anyways? is their any links to help me along? how big of a job is it?

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    Re: no heat + truck is running hot

    Quote Originally Posted by 98RhinoZ71
    How hard is it to install a heater core anyways? is their any links to help me along? how big of a job is it?
    There are six screws that hold on the bottom of the heater box. They are hard to find. The box is brittle, and will most likely break as you have to twist it a little to get it out, but GM sells new ones for about $45.00. This exposes the core, which is held in by a simple clamp. Take the hoses off at the firewall FIRST, then remove the core and put it all back together. It's really pretty easy, except for the tight quarters around the floorboards on the side of the trans hump, and sometimes the hoses are really stuck to the core ends. DO NOT pull them through to the inside! Clean them all the way off. There's a grommet that will be destroyed if you pull the core off with part of the hoses still attached.
    Some tips: use a little WD-40 on the hose ends to help them slip onto the new core. You need a second person to hold the core while you do this part. Be careful of the orientation of the clamps under the hood at the firewall, you want them on opposite sides of the hoses, not together, so that the release mechanisms are easier to use. It might take a very small socket set and extension to get that screw out that is nearest the trans tunnel. Ignore the factory manuals, Chiltons, and Haynes- they all say you must loosen the dash. You don't have to.

    HEY! Ignore this post if this is a NBS. They are apparently different. My experience is all with OBS.
    Last edited by porker; 11-24-2006 at 06:57 AM.

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    Re: no heat + truck is running hot

    Yea my truck is a 1998 do you still consider this the old body style I condsider it the nbs but im a old timer and think the 80's are the old ones

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    Re: no heat + truck is running hot

    Quote Originally Posted by 98RhinoZ71
    Yea my truck is a 1998 do you still consider this the old body style I condsider it the nbs but im a old timer and think the 80's are the old ones
    It is the old body style. I'm also an older poster, but the convention seems to be 1988-1998 = obs; 1999-2006 (7?) = nbs; the older ones are oobs (old, old body style). Ha!
    But, just take out those bottom screws, and if the box will come apart, then look to see if you can get to the heater core clamps. The air bag might make a difference. I've only done 1995 models, they don't have the passenger air bag. I can't imagine it preventing this repair, though.
    OH, BTW, I forgot that I was on my son's computer. I'm porker, chevysnbuicks' dad! I'm 53.
    Last edited by chevysnbuicks; 11-26-2006 at 07:39 AM.

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    Re: no heat + truck is running hot

    Alright new problem I dont know if it is my heater core now my truck is using alot of antifreeze i filled it up the other day and guess wut it took about a whole bottle! yea and it blew hot air finally but today It was low again on it and its doing the same thing again not blowing hot air and running hot I took the cap off its low again on coolant... no signs of leaking anywhere I have no idea wut is going on any clues? at all?

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    FSC's resident metal head chevysnbuicks's Avatar
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    Re: no heat + truck is running hot

    Quote Originally Posted by 98RhinoZ71
    Alright new problem I dont know if it is my heater core now my truck is using alot of antifreeze i filled it up the other day and guess wut it took about a whole bottle! yea and it blew hot air finally but today It was low again on it and its doing the same thing again not blowing hot air and running hot I took the cap off its low again on coolant... no signs of leaking anywhere I have no idea wut is going on any clues? at all?
    Sometimes a pinhole in the radiator can do that. My Roadmaster had a hole in the radiator that would leak coolant until the level got lower than the hole, then would only leak it while the engine was running. The combination of the fan blowing a fine mist over the engine compartment and the heat from the engine made it hard to see the water leak. But, after a while, the hole got big enough that you could see it after a fill-up. Water would sort of stream out of the hole. Look for signs of leakage around the sides of the tanks, usually on the driver's side, of the radiator itself. The other possibility, of course,is that you've blown a head gasket or cracked a head or block. I understand your '98 would have a vortec-headed 350 in it, right? Those vortec heads are just a bit fragile when it comes to cracking because of overheating. you might have both problems- heater core and blown gasket or cracked head.
    You should also check the heater-hose ends. They are made of aluminum, and if the previous owner of this truck mixed green anti-freeze with the Dex-cool, the ends of the hoses could be eaten away. It's really hard to see the leak on these, as one is in the back part of the intake manifold, and the other is on the front, near the water pump. Both places are in hot areas that tend to dissipate the water as it leak, so you smell it but don't see it. Easy change on those hose ends, BTW. Quick-release fittings that work with just finger pressure.
    If your housing that screws into the intake is leaking, taking it out can break it. There is a tool offered through Car-Quest called GM hose fitting removal tool that will take out the broken pieces if yours shatters when you take it out. Nice little tool for about $5.00. You get to use a BFH, also!
    Last edited by chevysnbuicks; 11-26-2006 at 07:53 AM.

 

 
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