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Thread: CLR in heater core?

  1. #1
    "Sign of the Cat" RUNnWYLD's Avatar

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    CLR in heater core?

    So its time to do a cooling system flush and was wondering if I should use CLR on my heater core. The cooling system is 100% stock and i know CLR isnt good for aluminum. Would this be a recommended way to flush the core on my 71 Cleavland?

  2. #2
    Contributor Ò¿Ó O'ville Stang's Avatar

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    I have a friend that used it to clean in his rad! It worked fine, car now runs way cooler!!

  3. #3
    pist'n broke member

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    if the rad or core is brass Id say no problem...if theyre aluminum & theyre old...and theres already some corrosion inside...the walls may leak if the CLR eats through

    vinegar is a very mild acid & is used to clean coffee makers...Im sure it would be ok inside the heater core...but it may not be aggressive enough

    to get all the scale out...would be good to see what the shops recommend

    I will add this though...if I wanted to de-scale the water jackets on an engine I was building Id use half water & muriatic acid

    & run water wetter...would really keep things cool

  4. #4
    Been around a LONG time

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    I've used it. Works mint, although I only let it sit for less than 10 minutes.
    Any caustic stuff should be flushed thoroughly before it damages seals and rubber hoses.

  5. #5
    Boost Goggles Apocolipse's Avatar

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    What about the motomaster rad flush stuff? Prob cheaper then clr.

  6. #6
    Been around a LONG time

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    ^^^ I have a bottle, but I'm afraid the crystals would chew up the seals moreso than the CLR.

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