The heater core in your Chevrolet Astro van, which acts as a small radiator in the engine cooling system, can get clogged with coolant and other contaminants over time. This prevents coolant from entering the system and causes the van's engine to overheat. If you can flush these contaminants out of the core so it can work again, you can save yourself the trouble of replacing the core altogether.
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Things you need
- 3/8-inch diameter tube
- Garden hose
Drain the coolant from the cooling system by placing a large container under the radiator's drain fitting and remove the fitting; you may need pliers for this, and attaching a 3/8 inch diameter hose to the fitting helps. Repeat the process for the drain plug at the engine block, then close the drains.
Remove the coolant reservoir and the windshield washer fluid reservoir from the engine compartment by disconnecting the overflow hose from the radiator, removing the washer reservoir's mounting bolts and lifting both containers out. This is only needed if the Astro is a 1994 or earlier model.
Detach the heater core tubes from the firewall within the engine compartment by loosening their hose clamps. Plug the hoses--rubber works best--to prevent contaminants from entering.
Insert a garden hose into one of the firewall openings for the heater core hoses; make sure the garden hose is connected to a faucet. Depending on the size of the hose and the opening, you may need to hold the hose in place while someone else operates the faucet.
Turn on the water for the hose and look for the water to come out the other opening in the firewall. Let the water run until the water coming out of the opening is clear.
Re-connect the heater hoses to their appropriate openings on the firewall. Re-connect all other components you disconnected, such as the washer fluid and coolant reservoirs.
Refill the engine coolant; use fresh antifreeze with a 50/50 mixture of water if the old coolant contains any contaminants. Add the coolant directly to the radiator through its filler neck until it's full, then fill the reservoir to the lower mark. Run the engine with the radiator cap off until the upper radiator hose gets hot, shut the engine off and let it cool, then fill the radiator to the lip on the filler neck.
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