Heater blows cool air

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COACHDOVE
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2001 Chevrolet Blazer with 70,000 miles. Heater started blowing lukewarm air.
I disconnected hoses to heater core and flushed it with a garden hose in both directions until water ran clear from both ends.
I also topped off radiator and let engine run with cap off to let any air out of system before replacing cap. Had hot air for about 1 minute after flushing core, but now its cool again. When I feel the hoses with engine running, the hose going in is very hot, but the hose coming out is cool and feels empty. Haven't found any leaks. Could this be a faulty core or is something else the culprit here? The engine seems to to never get near the halfway point (240 degrees) even when I run the engine at 3,000 rpm's in the driveway.
Nov 10, 2007 at 7:15 PM
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CHEVY22
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i would first suspect a thermostat, but there are other items that need to be checked; the water pump and the radiator. i would start with the thermostat it may be opening too soon or clogged.

let us know
Jim
Nov 10, 2007 at 9:20 PM
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ASEMASTER6371
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Good evening.

The fact that the other hose is cold, then that indicates a clogged heater core and it must be replaced.

https://www.2carpros.com/articles/replace-heater-core

https://www.2carpros.com/articles/car-heater-not-working

More dirt got dislodged and clogged up the passages.

Roy

Heater Core Replacement

1. Remove the heater/vent module. Refer to Heater/Vent Module Replacement .


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2. Remove the heater core access cover screws.
3. Remove the heater core access cover.


imageOpen In New TabZoom/Print



4. Remove the heater core from the heater/vent module.


Mar 26, 2020 at 3:50 PM
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