Question about 1999 Chevrolet Blazer

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Heater turnes to cooll air after a few miles driven

I took my wifes little Blazer in because the heater was not staying hot. I thought it might need a new thermostat so I took it to a repuatable repair shop. They said, that after a doing pressure test that the radiator and both hoses had leaks. So we had a new radiator, hoses and thermostat installed. Heater still acts the same way with after driving a few miles the hot air suddenly starts blowing cool. The car does have the Climate Control heater system but the problem is still there even when used manually. Any help would be appreciated. Thanks.

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I have seen many blazers have stopped up heater cores. most are fixed easily. you will have two hoses going to the firewall up top passenger area. you can undo them and get a garden hose with a hand sprayer and try to press against the metal line on your core and blast the water. it will come out the other side so watch out and also cover distributor with a plastic bag. repeat for other side. go back and forth a few times until you have a good flow and the water is clear. reconnect hoses and top off coolant. try this it doesn't cost hardly anything.

Posted on Nov 13, 2009

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The heater core may be "plugged". Take both hoses off and using a garden water hose, see if you can get water to flow in and out of both hoses. If it flows slow or a lot of gunk comes out, its plugged, just keep reversing the water until it flows freely in both directions. Then hook up the hoses, top off the coolant and test drive it.

Posted on Nov 13, 2009


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