Radiator/Heater Coil Issue on 2002 Chevrolet Blazer

When you flush your radiator, the heater core gets flushed as well. You will have to run the vehicle untill the heater is blowing hot air during the flush, that way its going through the thermostat. Empty the radiator as per normal and thats it.

my 98 Blazer I had to replace radiator water pump heatercore and hoses. Had head gasket go. Once that happens air and dexcool corrode cooling system. Do you smell antifreeze? Are you loosing antifreeze? Check oil see if its another color not clear or black but i think light brown. Have you flushed out system?

flush & fill is best -just fill is ok,you can fill it through the over-flow tank,(may take a while ) or remove the radiator cap & fill there

Flush coolant system out first with prestone or peak coolant flush if problem still exist replace heater core.

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Did you mean the only time it blows hot air is under acceleration?

First thing check the coolant level in the radiator. If coolant is low the first hing to stop working is the heat.

If the coolant level is fine but the coolant is muddy I woulds suspect a plugged heater core. You can try back flushing it by removing both heater hoses (engine cold) and then use a garden hose to flush clean water through the heater core. Do this on both pipes going into the heater core. Keep flushing until the water runs clear. Re attache the the hoses, remove the radiator cap, start the engine, let the engine come up to temp and top off the radiator with straight coolant (to comp for the water in the heater core). You may have to repeat this process several times over several days but you should be able to get it cleared enough to get sufficient heat without having to replace it.

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clean out the radiator hoses and make sure there's no stop leak in the radiator or hoses. also flush the heating coil out several times

I recommend flushing the radiator thoroughly if not done recently. there seems to be some sort of blockage in the radiator at this time. if you get lots of metal fragments that are flushed out during this flush, i will then recommend a rebuild on the radiator or replacement of the radiator. make sure the cooling fans are cycling on time as well.

open the drain valve on the bottom inside of the radiator, run the engine with the garden hose in the radiator cap, have the heater switched on high temp.  After the water comes out clean, turn off engine and let all water drain out.  Replace with 50/50 mix if distilled water and antifreeze.  Collect old antifreeze as it is very toxic and poisonous. 

Yes the issue is most likely an air block, jack the front of the truck up as far as you can, fill the recovery bottle and run the engine for about 10 min, then shut down and run cold water over the radiator, this should purge the air, recheck the recovery tank and refill as ness.