No heat in 1998 Jimmy

I have been struggling with a problem in my Jimmy that I am hoping someone can help me with. I am getting very little heat from my heater. I have checked the coolant level as well as replaced the thermostat but still no
joy. The temperature gauge appears to be showing the motor is operating at the correct temperature. I have 74K miles on the truck and I had the coolant replaced at 50K miles. If anyone has any ideas as to where I should look next, I would love to hear them.
Thanks in advance,
John
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at
should
One of three things:
1. Vacuum line to heater core bypass valve is cracked/broken/missing 2. Heater controls malfunctioning not allowing vacuum to heater core bypass valve 3. Heater core is plugged
I'd remove both heater hoses first and flush the core out with a garden hose, REVERSE the direction of normal coolant flow.
Doc

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Doc,
Thanks for the reply. I appreciate it very much. I know what I will be working on in the morning!.
John

bypass
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No problem, let us know how it turns out.
Doc

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doc, wanted to add another possibility, friend of mine had a 98 envoy with a similar problem....these truck actually have no bypass, the coolant is always running through, but for some reason she kept gettin an airpocket in the core, as a matter of fact the core is a little bit higher then the top of the radiator, and any airbubble will stay in there, and you may have to flush it fill it and the bleed the air outof the system
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