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Have changed the brakes from an V2 sti model to my impreza, bled them properly Front Right ->Rear Left ->front left->rear right, I have done this a couple of times, first with some fish tank hose and a one way valve on the end so I could do it alone, but after I found this problem I got someone to help me and did it slowly and just single push then open nipple close nipple while pedal still held in but I am still getting the same result. The pedal feels hard when the car is not started but as soon as i start it the pedal goes way down. Not to the floor but moves about 5 cm from the unstarted position. I have swaped a different booster in there to see if that changed anything but no joy. The one way valve in the vacum line is working. The car pulls up but the pedal feels very soft.

Any ideas ?

Do it my controversial way...

Open the bleed, pump the pedal 3-4 times or until smooth clean stream of fluid flows, close the bleed. Do it for each corner in no particular order making sure the reservoir is kept full.

If you haven't changed the master cylinder you'll find it takes more stroke to push the big pistons out too so make sure you have the right master.

You need the master cylinder from the donor car.

As already mentioned you will need the master cylinder that went with the brakes to give original feel. Your brakes will work fine the way they are but will always use alot of pedal

the master cylinder is the one from the donor car, and nice clear fluid is coming out of the bleed nipples (has had about 2 litres of fluid pumped through the system) and no bubbles after bleeding the pedal is hard as a rock, but as soon I start the car the pedal just goes way down and feels really soft will take it for a brake test to make sure it passes, the car has to have a engineering certificate to get legal again, and more to the point just want to make sure that the car stops all the time and does kill me or my son.

Another thing I noticed is that when it is off and i push the brake pedal I can hear a whoosing sound not sure if this is significant or not

SWK is a very long pedal normal in an impreza, the rs I had was nothing like this

did u put the booster on from the Donor car to?

same booster, swapped for another gc8 one but same problem

Adam, bleed it again using my method...

Hey Adam

The softness your experiencing when you start the car is the brake assist booster working as it should.

If everyone jumped in their car put the foot on the brake, started the engine they would find that their brake pedal will drop and go "soft". This is due to the engine vacuum doing some of the work.

The other thing to look at - the brake pedal - does it have the same push/pull point as the donor car?

I'm sure your brakes will be fine, you may just have a really good booster there and you'll find your brakes may be a lot more touchy...

Give it a go at low speed (where you can resort to hand brake if need be) and see how it goes.

Cheers

Bennie

PS i'm late for uni

Ben wrote:Adam, bleed it again using my method...

will give it another try, brake fluid is only $6 a bottle so not much to worry about.

You dont have ABS do you, as they can be a prick to bleed.

The Impreza should have similar pedal to the RS.

Liberty brakes are split front and rear.

Are all your brake lines tight?

Can you back off the master cylinder a bit to see in behind it to see if it is leaking, if it had been stored for some time the seals harden up.

Definately does sound like you have air in the lines somewhere. Try undoing the bleed nipple a bit on the front calipers and put your finger firmly over it while you get someone to push the pedal down slowly. I have had trouble before on fronts not filling up properly but have not found a fool proof way to get the air out yet.

You may need to prime the calipers but if you arnt getting any air come out any more the problem, if there is one, may be some where else

If all else fails see a Subaru specialist .

Lastly , check your pedal box against that of the donor car - sometimes they are different . Also check if the donor car had a master cylinder stopper bracket to support weak flexible production cars fire walls . Flex = travel too .

Cheers A .

What were the calipers like before you put them on(have they got shit in them)I have had a couple gum up from no use and the caliper slides wernt budging at all giving a spongy pedal.......just my 2 cents....