Question about 1998 GMC Envoy

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Cold and no heat

I have a 1998 GMC Envoy had my fan clutch replaced a few months ago because I had only cold air blowing, had heat again. now I'm back too no heat changed the thermostat and it's still blowing cold. I just wanted too know if I missed a step or if this is a sign of another problem. Please Help!!!

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This is a common complaint for the 4.3 v-6 by GM, what happens over time is air gets into the cooling system, usually a small coolant leak at the intake manifold gasket. Ait gets in the cooling system and starts electrolisis. From this the coolant starts to solidify. If I'm correct your heater core is plugged. Remove the radiator cap (engine cold only) and inspect the coolant. The proper color should be red. If the elctolisis is taking place the coolant will turn to rust and look like mudd. If you find mudd in the radiator, most likely the heater core is plugged. This is a very expensive repair. You'll need to remove the raditor & sent it out to be boiled out. Replace the heater core, thermostat and the coolant hoses. You'll also need to perform a "prestone" flush. You may need to flush the cooling system monthly until the system is clean.

Posted on Apr 15, 2009

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