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Old 01-12-2022, 06:57 PM   #1
Kostamojen
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Member#: 2272
Join Date: Sep 2000
Chapter/Region: BAIC
Location: Fire Caves
Vehicle:
2019 Macan 4cyl
1993 Impreza FWD WRX swap

Exclamation Brakes won't Bleed: Complicated Non-ABS Impreza brake problem, looking for ideas...

Alright, this is a little complicated, so I'll start with the car. Its a 1993 Base model Impreza turned into a track car. You can read more about it here:

https://forums.nasioc.com/forums/sho....php?t=2916708

Right now, the brake system consists of:

Rockauto 4-pots up front
02 WRX rear calipers w/ H6 rotor upgrade
Stoptech brake lines all around with Stoptech pads
JDM Type-RA Non-ABS brake proportion valve
2002 Impreza TS 4-port Non-ABS master cylinder
The original 1993 Single stage brake booster
Hill holder has been deleted

The problem I'm having is I can't get the brakes to have pressure. I'm not seeing ANY bubbles during brake bleeding, I've tried two separate brand new master cylinders both bench bled. I disassembled the first one and didn't find any evidence of the master cylinder seals being blown. The brake lines are not leaking, I've inspected all of them.

I ran the car with the stock proportion valve and stock master cylinder (3 port not 4 port) with the hill holder for track days and autox in 2020 and 2021. I had issues with the rear brakes locking up (the car spun once at speed getting on the brakes too) and brake feel being poor. Previously with a 1995 Impreza non-ABS I had, I ran it with a SVX non-abs master cylinder and that car had EXCELLENT strong feeling brakes plus no issues with brake bias but I never tracked that car just a few autox's and daily driving.

I decided to add the JDM proportion valve and I heard about folks using the 2002 TS master cylinder instead of the SVX master cylinder after it was discontinued, but I didn't know about the 3-port/4-port difference. So I first tried the car with plugging one of the master cylinder ports and it was OK but had terrible brake feel, so I went with deleting the hill holder and routing the brake lines to the master cylinder directly (since the hill holder acts like a T in the brake lines).

So ya, I've bled the brakes maybe a dozen times, gone through 8 containers of Motul 660, bought a Motive pressure brake bleeder, and so far I can't get the master cylinder to pressurize properly at all. I've done the pump pedal solo method, the pump the pedal with an assistant method, just using the Motive bleeder, using the Motive bleeder plus both the other methods, and NOTHING is working. Tried this with two separate master cylinders as mentioned same result...

So whats the issue here? Is there a bad kink a brake line possibly causing this (nothing I can see)? Is the master cylinder not cooperating with the brake booster? Is something going on with the proportion valve? Have one of the brake bleeder screws had an issue? Is there something else I haven't thought of yet? I'm stumped and have a time issue too as the car needs to be smogged by the end of the month or it has to go non-op...

Here are a couple photos for reference:





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Old 01-12-2022, 07:42 PM   #2
Kostamojen
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Member#: 2272
Join Date: Sep 2000
Chapter/Region: BAIC
Location: Fire Caves
Vehicle:
2019 Macan 4cyl
1993 Impreza FWD WRX swap

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Just quickly measured the clearance between the new TS style master cylinder (since I have a spare one now laying around) and the old stock 3 port master cylinder, and they have the same clearance. So its not the master cylinder to brake booster clearance issue...
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Old 01-12-2022, 08:11 PM   #3
Kostamojen
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Member#: 2272
Join Date: Sep 2000
Chapter/Region: BAIC
Location: Fire Caves
Vehicle:
2019 Macan 4cyl
1993 Impreza FWD WRX swap

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Does anyone have a diagram for the 4-port brake system and master cylinder? I can't find one showing which port goes to witch brake.
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Old 01-14-2022, 11:14 PM   #4
Kostamojen
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Member#: 2272
Join Date: Sep 2000
Chapter/Region: BAIC
Location: Fire Caves
Vehicle:
2019 Macan 4cyl
1993 Impreza FWD WRX swap

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So I tried bleeding the brakes one more time, this time using the pattern as described in the FSM's:



Prior to this, I was doing the "farthest to closest" method.

I went through once just doing a basic bleeding, and there wasn't a change. So I used the Motive kit again, and still no change, but I noticed the pedal was stiffest when I finished the front left (passenger side) caliper. So after doing all 4, I went back to that pass side front caliper and did that one and left it as it...

The pedal works now, but it still feels not good. It won't stiffen up 100%. I'm not sure whats going on still...
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Old 01-22-2022, 05:30 PM   #5
Kostamojen
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Member#: 2272
Join Date: Sep 2000
Chapter/Region: BAIC
Location: Fire Caves
Vehicle:
2019 Macan 4cyl
1993 Impreza FWD WRX swap

Default

So I figured it out...

Got a cheap tool to measure the distance between the brake booster and the master cylinder. Spec is supposed to be .020" but it was more like 1mm (.050" or so).

Wound up adjusting the brake pedal to fix that clearance, and the pedal is MUCH better now, super firm in fact. I knew there couldn't be an issue with the fact that there was no air in the system and no leaks and basically nothing wrong that I could find. All is good with the world now
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