Brake problem 505 STI - Booster or compensator valve??
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  1. #1
    Fellow Frogger! 604 tragic's Avatar
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    Aug 2003

    Default Brake problem 505 STI - Booster or compensator valve??

    Our 505 STI is being readied to pass on to teenage son on P plates,but the bloody brakes are now not working properly. Mater cyl is OK & I suspect either Booster or rear compensator valve.
    How hard is it to change a 505 booster?? Any tips or traps?

    When braking, it seems like only the rear brakes are working. This happened a few days after I got 2 tyres from KMart (not recomended - like McDonalds - you'll need a wheel alignment too blah blah) But before I could stop them they jacked the rear way up off the ground by the diff only!!! Would this bugga the rear compensator valve? It doesnt seem to be leaking & there is still movement of the piston (3-4 mm) is this OK?

    The Booster does hiss but it seems to pass the 'start with foot on pedal' test.
    I remember the 604 had a gotcha when changing boosters as it is offset from the pedal box & makes it complicated. Is it the same in the 505??
    How much is a reco booster these days?

    So many projects - so little time.

  2. #2
    Fellow Frogger! Ralph's Avatar
    Join Date
    Jul 2001


    Replacing the booster is a bit of a job but not too bad. There's four bolts holding it on up behind the brake pedal, once you've undone these there's a clip that holds the shaft to the brake pedal top that can be tricky to get off and even trickier to get back on. The master cylinder comes off pretty easily and the actuating rod pokes into the back of it. Check the vacuum hose connecting the booster to the manifold first as these often deteriorate. Also the white bit of plastic the hose plugs into on the booster is a one way valve that can get stuck. Check these first before pulling the booster off.

    European Auto Imports has boosters for about $250.

    Jacking it up by the diff, although not the preferred method, shouldn't damage the compensator.

    On the internet, no one knows that you are only wearing a fez.

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