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?