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Brake issues


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Need the forums help diagnosing what my brake problem is.

Car is v3 sti ra with 4 pots. The pedal feel feels like it doesn't start braking till about halfway down the pedal travel.

Whats been done so far:

Full brake bleed with genuine subaru dot 4 fluid, new rotors, rebuilt 4pots using new seals etc, pistons of brakes are good and everything is clean, new pads

So tested brakes out and pedal feel hasn't improved much.

Then thought, oh might not have bleed it properly so got dba 650s and new pads again, full bleed with motul. I found a post on here that talks about the order of bleeding as my friend and I went right rear, left rear, left front then right front.

That was the first bleed.

When the dbas went on, another bleed was done using the screenshot of the workshop manual saying to bleed from drivers side, then left rear then left front and right rear with motul brake fluid.

Braking feel has improved slightly. I am pretty sure we have done a thorough bleed using two 500ml bottles per bleed.

What are my next steps I can try to improve the pedal feel? Brake booster? Goodridge braided lines?

How can I test brake booster?

I have not done the back brakes yet but pads seem meaty and rotor has no lip, there are no shudders or anything. Handbrake all good.

Any help or suggestions greatly appreciated

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Phone photos showing orientation of 4 pots, sorry about the quality.

20120320101031.jpg

20120320101016.jpg

Slides? you mean the pins that thread through the caliper and brake pads?

Got this image off a v3 sti thats on trademe at the moment which seems to have them mounted the same way as I do

210447366full.jpg

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I helped dzk with his brakes & can confirm only one nipple on each of the front 4pots and is at the top. When rebuilding them noticed only slight nicks on edge of the a couple of pistons (mating surface to pads/shims) but looked in pretty good shape. Wondering how much the shims affect brake sensitivity, I guess the more you have the more indirect the braking pressure would be?

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So what else can be tested? checked? goodridge braided brake lines? Is there a universal test for brake booster? Anyone in Wellington keen for me to bring car around and they test the brakes to see what they think it could be?

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Using the one man bleeder with two people. So one person connecting the bleeder and refilling reservoir and other pumping the brake pedal slowly until new fluid bled through. Done this twice, once doing from the furthest from the reservoir to the closest. Then using this method from the sticky

brakessubie.jpg

and still no real change

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seems to be only half the instruction there :)

here is my failsafe way of bleeding brakes

2 people

a clear plastic tube( 1/4 inch to fit over nipple )

a container to catch the fluid in

1/fill master cylinder

2/fit tube to bleeder

3/pump the pedal a few times then hold it down

4/second person open the bleed valve( pedal should go to floor) watch for bubbles in tube

5/close bleed valve

6/repeat 3/4/5 a few time at each wheel

should negate that it is a bleeding issue

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  • 2 weeks later...

Is there an easy check for faulty master cylinder rex-leggy?

Cudda, going to change all the brake lines to braided goodridge this weekend. 4 pots were overhauled with genuine subaru seals etc. Will look into new rear pads if they look worn.

They are only silverline pads on the rear (car came like that) so perhaps replace those while I am at it.

Been expensive the last couple of weeks. Cusco Master Cylinder brace $177 and goodridge lines $190 just today

I think with the cylinder brace, it improved the hardness of the pedal feel about 10-15% so hopefully the lines and rear pads help somewhat.

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by clamping the rubber lines first will let you know whether the master cyclinder is where the problem is at, & if its solid then its just a case of releasing Front left / right or Rear left / right caliper hose clamps to determine where the pedal gets soft, could be a case of all of them combined too, rear caliper slides if single pot's

so best to start clamping befpre you change to braided lines,

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