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Thread: 09 Impreza Power Steering Fluid Hiss

  1. #1

    09 Impreza Power Steering Fluid Hiss

    Hello everyone, saw the thread on a power steering pump rebuild and all the useful information that came from it and I figured I'd get some input on the power steering hiss noise that plagues a lot of the newer Imprezas 2.5i and STI (from my observation, please chime in if this has always been a problem)

    Did some research into this issue and found that it was "normal" (proper fluid levels, no leaks) for there to be a hissing noise coming from the power steering pump especially during parking situations. What alarmed me though is a whole thread I found dedicated to people installing a power steering fluid cooler that claimed to eliminate the hissing noise and prolong the life of the power steering pump along with any associated seals. Could this be a key piece of "maintenance" that will prevent something more major such as a steering rack seal leak down the road (theory being that the boiling power steering fluid is harder on seals)?

    0529101841b.jpg7389594108_e804d4b6f0_b.jpg

    I'm usually not a fan of these DIY mods that stray from the factory design but could this really be beneficial for the car? Also it seems most of the people that performed this lived in warmer States down south. Can the fluid become too cool to circulate efficiently during our harsher winters?

    Any input into this will be much appreciated
    Martin Wong
    2009 SSM STI

  2. #2
    Martin,
    I had hissing noise when ps fluid levels dropped, that was only addressed when I had the rack rebuilt. I had a pinion shaft leak that wasn't apparent for a while because the splash guard/belly pan collects it. Are your PS fluid levels low?
    Laszlo - red '17 WRX
    The all-new Subaru WRX is coming. Pardon our dust.

  3. #3
    The second photo looks like a JDM STi PS cooler. I use the GD version.


    Stephen - I drive Blue Subarus of the rally and track varietals.

  4. #4
    Thanks for the reply guys.

    Las Yes I checked the level and it is right on. I've heard switching the fluids over to something like Redline is a temporary fix.

    Steve: Did all GDs come with a PS fluid cooler or just on certain JDM models? The unit pictured above is a Group-N JDM item. Key question, is this a worthwhile investment/install?

    -Martin
    Martin Wong
    2009 SSM STI

  5. #5
    I think that cooler was on JDM STi's only.

    I believe in keeping fluids cooler. I've used both Mobil 1 ATF and Amsoil tranny fluid in my STi and never felt a difference between them, nor with the cooler vs. without. If you've felt your PS reservoir after a long track session, it seems to make sense as a preventive maintenance measure. I'm glad that I did it.

    GR's seem to have an issue with this so using quality synthetic fluid and keeping it cool makes sense. Make sure that the piping is big enough to not restrict flow.


    Stephen - I drive Blue Subarus of the rally and track varietals.

  6. #6
    Thanks for the input everyone, I will see if something like this does the trick: http://www.summitracing.com/parts/der-13200/overview/
    Martin Wong
    2009 SSM STI

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