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Gmc9305

2005 sierra crew cab 5.3l heat issue

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2005 sierra with 92k. Bought a year ago with 82k and the problem existed when purchased.

On cold days I can warm up the truck upwards of an hour and have no hot air blowing. Blower motor works, engine temp stays steady at 210f. If I rev the throttle to about 2,000 rpms, warm air will come out but gradually decrease as it sits idle. Also, it takes about 15 minutes of steady driving before it gets real hot.

 

I'm thinking thermostat, water pump issue, or blockage?

 

Any suggestions appreciated.

Edited by Gmc9305

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Could be one of many issues. What does the temp gauge say? Could also be a blend door actuator.

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Reads 210. Is the blend door actuator behind the control panel? Been driving for about an hour and a half straight at slow speed and heat is good...

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Blend doors are behind the dash. About a $1500 dealer fix

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I actually don't think it's the blend door actuator. I ran it through all the selections and all work. Could it be air in the system? Occasionally I will smell some coolant.

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Flush the heater core for starters

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Good temp reading suggests pump and thermostat are working. When running dry for heat and then try to hold the water lines feeding the heater core thru the firewall. If one is cooler than the other - then blockage in heater core. If both hot, then door/actuator.

 

Sent from my XT1053 using Tapatalk

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So I let it cool and checked the coolant and it was low. I added about 1/2 gallon. Could I be loosing coolant through the overflow due to boil over or bad thermostat? I do smell coolant from time to time. Tomorrow morning I can check to see if the coolant was the issue.

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Sounds like a blend door to me. $30 or $50 Fix two 5.5MM Bolts

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I just added a 1/4 gallon more to top off. Both heater hoses are equally scorching hot. Temp just under 210.

 

What would cause the loss of coolant then? Separate issue?

 

The air temp has stayed hot all day since adding coolant even at idle. I think low coolant was a factor, but I don't know how I'm losing it except maybe through the overflow cause I smell it sometimes.

 

Could the blend door still be part of the problem?

Edited by Gmc9305

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Loss of coolant could be bad head gaskets. Have you checked the oil?

 

Heater core leaking? Check the carpet on the passenger side.

 

Rad have a small leak? Look carefully at the plastic side tanks.

 

Could still be a blend door.

 

Find the blend door at the bottom of the dash in the very middle. Look and feel for the hole / knob on the actuator. Place finger over the hole and change the control from heat to cold and see if the door actuator moves. If not thats the problem.

 

That is an easy fix. Two 5.5 MM bolts and one plug.

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i had the same issue. turns out my thermostat housing was corroded inside and wasn't allowing pressure to push water through my core. so on high speeds all i got was cold air. its also possible your electric hot cold actuator isn't working. id check that first. its under the dash around the passengers left foot area. there's 2 small bolts. remove it but leave plugged in. turn the dial(with key on) check to see if it actuates. if it doesn't. than that's your problem. if ti does id check the housing. its not expensive and at least its an easy fix.

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So far I've seemed to correct my problem by adding coolant, over half a gallon. So I think the issue may be that I'm loosing coolant somewhere (I think through the overflow) and not an actuator because everything it is working as it should.

 

I'm going to pressure test the system and go from there. Initially I was thinking I had a stuck open thermostat and it was taking a little bit to get warm.

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So tonight I smelled coolant when I passed in front of the truck. I checked around the coolant tank and there's evidence of coolant coming through the overflow tud and running down the wheel well.

 

Any idea why I constantly keep loosing coolant through the overflow tube?

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