Bleeding cooling system air

Discussion in 'General Motoring' started by Rick Courtright, Aug 7, 2008.

  1. Hi,

    I think we all know how Subies are about trapped air pockets when
    refilling coolant...

    I also have an old Toyota truck w/ the 22-R engine, which some of you
    know is also a problem child WRT trapped air. I've had a couple of 'em,
    and they've given me fits at every coolant change. I've gone thru all
    kinds of gyrations, and stumbled on this idea totally by accident, but
    it's worked quite well at the last coolant change and again the other
    day when a new water pump went in. My Subie's dead right now, but I'll
    try this trick on it when I put it back in service.

    I took an old radiator cap, and drilled a tiny hole (maybe a half
    millimeter?) in the little metal piece in the inner center of the cap.
    This is the piece that stays closed under pressure (engine hot), then
    opens under vacuum (engine cool) to allow coolant to flow back from the
    overflow tank. You can identify it by pulling--it will open under spring
    pressure. Drill the hole toward the center (inside the sealing ridge at
    the outer edge.)

    Once the system's been refilled, install this cap instead of the normal
    cap. Run the engine to normal temps w/ the heater on full and all the
    usual precautions (front of car higher than rear, watch the temp gauge
    carefully and all that.)

    What's happening is the system is essentially "open"--it holds no
    pressure--BUT w/ a cap installed you don't have the violent bubbling and
    eruption of coolant all over the place you often get if you run w/ no
    cap. This seems to help the coolant flow thru the system more easily
    than if it were under pressure, allowing air to move out of the nooks
    and crannies where it often gets trapped.

    Shut the engine off, let it cool, refill as required. Repeat the cycle
    once and cool again. Check again, refill again as required, install the
    proper cap, and test drive. Watch coolant level for a couple of days and
    top off as required.

    Hope this helps some of you who've been scratching your heads over
    trapped air...

    Rick Courtright, Aug 7, 2008
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  2. Rick Courtright

    Bob H Guest

    Can you post a link to a photo of the drilled cap? Your idea sounds very
    Bob H, Aug 9, 2008
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