# 2000 gmc Sierra No Heat



## BillyRgn (Jan 28, 2004)

Anyone ever have this problem, the engine temp is normal, but the heat will only come out at outside temp. It did not work for a couple days and then it worked for a day and now it doesn't work again, all this is according to my brother who has been driving that truck. The truck is a 2000 gmc Sierra 2500 sle with the 6.0 vortec this is the new body style I checked it myself last night and the engine was at normal operating temp, the coolant level in the resvoir was good and it was dry under the heater core, the heat was about the same temp as the inside of the truck on leval 5. Usually on 5 you have to turn it way down after a few minutes because it is usually very warm. Anyone have this problem before? Thanks in advance - Billy


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## larboc (Dec 8, 2009)

Does it have a/c?


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## mayhem (Aug 25, 2006)

Had the exact same issue with my 2000 Silverado 2500 6.0 a few yearsa go.

With the engine up to operating temperature pop the hood and touch the two coolant lines that go to and from the heater core, they're the two thick black hoses that go into the firewall on the passenger side. I bet one of them is untouchably hot and the other is nice and cool. If this is the case, your heater core is plugged up, possibly from not changing the Dex Cool coolant in the system. Let the thing cool off, then pull both lines off the firewall and push them out of the way, take a garden hose on a low to medium setting (do NOT use a nozzle for this, just a running hose) and run the water through the core in both directions. With a bit of luck your core os fine and just plugged up, running a steady stream of water through the core in both directions should loosen and blow out the gunk thats stuck in there and get you back in shape. When I did mine I got a big plug of what looked like enough coffee grounds to make a full 12 cup pot of strong coffee. Ran the water back and forth in both directions till it flowed totally clear, reattached the two hoses (make sure they go in the right place...might want to mark one of them), topped off the system and burped it to get the air out and its been working great for a few years now.

Hope this helps.


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## deicepro (Mar 24, 2009)

I would check the heater core lines like the post before me ^^^^^said
Or like what happened on my truck, the motor that selects the heat could be stuck between hot and cold...


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## BillyRgn (Jan 28, 2004)

larboc;1361257 said:


> Does it have a/c?


Yes it does


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## BillyRgn (Jan 28, 2004)

Thanks for the quick response I will try that tonight and keep you posted


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## mayhem (Aug 25, 2006)

Had to dig a bit to find it, but here's the original thread.

http://www.plowsite.com/showthread.php?t=55423


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## cubicinches (Oct 19, 2008)

Or the heater control in the dash is bad... fairly common problem with those trucks.


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## mayhem (Aug 25, 2006)

The heater core lines will tell the story here.


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