I have a 99 blazer and just recently my heater stopped working. It blows air but just not hot air. I think my heater core might be clogged or maybe it is the thermostat. If anyone has had the same problem or has any suggestions it would be greatly appreciated.
Thanks!

 

Sounds like a plugged heater core, real common if you still have the Dex-Cool in the radiator. I would flush the core, flush the coolant, and replace the t-stat, and radiator cap. Use the green coolant as a replacement. Korey

 

Thanks, I think I will try that.

 

Make sure that it is truly the core and not a stuck t-stat, if you can feel a major difference between the heater core hosesnear the firewall next to A/C then you have a plugged core.

To flush the core you will need to attach a garden hose to the heater hoses, first the closest won to the middle (outlet) and listen for a sudden whoosh (plug being forced out and water beginning to flow), let it flow for a few more seconds. Then switch the garden hose to the other connection and let the water flow in that direction for a few seconds (30+) to see if flow has been completely restored. Then for good measure repeat the process. These instructions are for the core only.

To flush the dexcool if preferred then you will have to remove the plugs in the lower side of the block they should be near the motor mounts, they should take a 3/8" square drive to loosen if not then you will have to make tool fit.

Once you get all the DexCool out then i would recomend using the Yellow Prestone, it is certified to work with all other types of coolant and if you don't get 100% of the DexCool out then that would work better than the green. Plus the Yellow is an extended life coolant similar to DexCool, but not chemically the same.