OK to flush heater core with Drano, Limeaway, or CLR?

My 1994 Chevrolet Corsica is putting out lukewarm air from the heater. I installed a new 190 degree thermostat with no improvement. I have verified that very hot water is being sent to the heater core from the water pump. I know that the vacuum-controlled "flaps" in the air duct are working because I can hear them when I adjust the selector knob, so it must be the heater core.

I bought a heater core, then found out that the car must be lifted and placed on jackstands, the dash removed, and a lot of other awful things just to change the heater core.

Rather than go through all this, will it work to disconnect the two water hoses from the heater core, blow the coolant out of the heater core, then pour in either some Drano, Limeaway, or CLR, let it sit awhile, then flush it out with a garden hose?

Reply to
j
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Drano is the opposite of the other two. It's an alkali intended to break down grease. You don't have grease in your lines. Limeaway and CLR both are acids that are intended to attack corrosion.

I suggest that if you want to try something like this, you use Prestone radiator flush, which is an acid much like CLR but which has been tested fairly well in cooling systems.

You should know, however, that if you have a heater core that is plugged, it may also be well on its way toward leaking, and cleaning it out with the radiator flush may take it all the way over the edge. But it cannot hurt to try; the worst case is you'll have to replace the core anyway.

--scott

Reply to
Scott Dorsey

If nothing else works, try taking the two heater core hoses off and GENTLY reverse flush your heater core with a garden hose. This may be a last resort and it could make your heater core leak, just like all the other methods you mentioned.

Reply to
Kruse

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