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Hot engine...but no heat from heater

Hot engine...but no heat from heater

Postby 4thgenZ71 [OP] » Dec 27 2012, 7:23am

I need some help/thoughts on this one. I'm sure it's something simple that I'm missing but I'm at a loss.
Engine temp rises to 240+ after warmup while in idle and while driving. Heater only blows out cold air. Changed thermostat but no change.

Thanks in advance,
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Re: Hot engine...but no heat from heater

Postby 035.3Z71 » Dec 27 2012, 7:25am

Maybe there's a blockage in your heater hose?
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Re: Hot engine...but no heat from heater

Postby dan89 » Dec 27 2012, 7:26am

check the heater core. many times the hoses that run in or out gunk up. If your lucky a couple squeezes of the hoses to break up build up and you might be able to free them up for a short time fix! They also make a flush kit for them that is pretty simple to use or you could just take off the hoses and flush water through it with a garden house. The hoses are easy to find they are on the left side of your engine compartment going through the firewall near what would be the back side of your glove compartment. If your engine is hot and the heat is on, both of these hoses should be warm or hot to touch. If one of them is not warm, your problem is most likely here.
Last edited by dan89 on Dec 27 2012, 7:39am, edited 1 time in total.
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Re: Hot engine...but no heat from heater

Postby 4thgenZ71 [OP] » Dec 27 2012, 7:37am

Thanks for the quick reply. Antifreeze? Check! I'll check the heater core in the morning and see what I can do to flush it.
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Re: Hot engine...but no heat from heater

Postby dan89 » Dec 27 2012, 7:42am

4thgenZ71 wrote:Thanks for the quick reply. Antifreeze? Check! I'll check the heater core in the morning and see what I can do to flush it.



no problem. good luck!
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Re: Hot engine...but no heat from heater

Postby ASTE25 » Dec 27 2012, 1:05pm

When the engine is warm feel both heater hoses. If one is cool and one is hot then you have an obstructed heater core (or a bad heater core valve, if it has one. some vehicles use a mechanical valve to turn the coolant flow on and off to the heater core). If they are both about the same temperature I would say you have a problem with a blend door actuator.
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Hot engine...but no heat from heater

Postby 01darkhorse » Dec 27 2012, 7:15pm

I had a s10 that had air in the line. Burped it and had heat after that. Just my experience
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Re: Hot engine...but no heat from heater

Postby soap » Dec 27 2012, 7:35pm

You know, I've never dealt with the cooling system on one of these trucks. Are any of the newer ones what I call "entrapment" engines, or is the radiator still the high point in the system and there are no bleed screws to open if you get air in the lines?
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Hot engine...but no heat from heater

Postby Machster69 » Dec 27 2012, 8:03pm

The reservoir is higher than the rad...
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Re: Hot engine...but no heat from heater

Postby soap » Dec 27 2012, 8:04pm

Thanks. And no air entrapment points?
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