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Proper way of burping the coolant system?

rcnacura May 29, 2018

  1. rcnacura

    rcnacura US Spec 8V

    So I went and did a track day and my water temps went into the red alot. Car then did the warning to let the car idle. So if back of the throttle and then the temps would eventually go back to "normal", but as soon as I did some wot passes out will come up again.

    I opened the coolant reservoir to release any air, but didn't really make a difference. Refilled, let it idle and air was releasing but still not much progress. Never had this happen before, but I did just take off some coolant hose to replace an oil line in the turbo last week.

    Any tips/suggestions on how to properly get all the air out? Or if you think it might be another issue, please do let me know your thoughts. Tia

    Sent from my Pixel 2 XL using Tapatalk
    racerboy55 likes this.
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  3. farmerpalmer

    farmerpalmer Registered User

    I suspect it was not air, but steam. As water boils, it turns to a gas. When it cools, it returns to liquid.
  4. rcnacura

    rcnacura US Spec 8V

    But it's a closed system so it shouldn't create hot spots and overheat.

    Sent from my Pixel 2 XL using Tapatalk
  5. Chris43

    Chris43 Registered User

    Antifreeze should lift the boiling point of the cooling water way above 100°C anyway
  6. MrFlibble

    MrFlibble Guest

    There are no cooling system bleeders to allow air bleeding, and as a result no reliable way to purge air already in the system.

    The workshop manual requires the system to be drained and then refilled under vacuum.

    A technique I have found useful on other cars is to use a "zero pressure" radiator cap. By preventing pressurisng the system air bubbles will be larger so more likely to bubble out. You can easily make a zero pressure cap by removing the seal mechanism or drilling a hole through the cap.
    Last edited by a moderator: May 31, 2018
    rcnacura likes this.
  7. T-800

    T-800 Guest

    Having recently completing a GTD MK 7 timing belt replacement I purchased a vacuum filler


    Works perfectly by utilising compressed air rushing by a Venturi, this causes a vacuum in the coolant system (hoses collapse) you then can introduce fresh coolant by opening the system to air, this sucks in the coolant and refills the system in minutes, with no air locks.

    Very quick and easy.....if you have a compressor.

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