Audipwr1

Hoping the brain trust can help here.

Car came with a low and soft pedal (engagement well towards bottom of pedal range, not a firm feel).

What I have replaced
Brake Master
Did stainless brake lines from hard lines to caliper
new pads
new rotors

No change / bled the system twice / drove it 100 miles between the master job and the other parts.

I guess whats left is ABS unit and booster? Ideas?

FDAUTO

iTrader: (4)

What was your bleeding method and how is the bite as you press the pedal? How much of the travel is dead space?

Audipwr1

Round 1:
new lines/pads/rotors - pressure bleed
Pedal feel low and not changed

Round 2:
New Master
Pressure bleed
No change

3/4 travel is nothing

Bite does feel a little mushy and very low - I would typically say oh its air in the system, but the fact that it was bled twice (professionally at a shop) didnt change the feel of the pedal as it was before (with super old fluid in it when I got it) - I dont think its air - but I dont personally know for 100% certain it isnt, the shop I used is good / methodical / but arent themselves RX7 Ninjas - so if there is some trick to this car to bleed it that is weird / nuanced that would be helpful data to know

DaveW

Did you check caliper function? Are the pads on both sides of the rotors making firm contact with the rotors (show similar wear pattern on both pads)? If not then something may be amiss with one or more of the calipers. Any pull to one side under braking? That is also a sign of a caliper misfunction such as a binding piston, slide pin, etc.

A caliper issue could cause the caliper to be flexing the caliper mount and/or rotor due to uneven loading, and you could be feeling that flex.

gracer7-rx7

iTrader: (16)

There's nothing special about bleeding the FD's brake system so you probably have the basics covered.
What you could be experiencing is some sort of leak at the calipers. They can sometimes leak at the bleeder screws or at the pistons depending on what might be worn out. I've dealt with old calipers where the threads in the caliper where the bleeders screw into was worn and leaking brake fluid - therefore soft pedal. Need a very careful visual check of the bleed screws for that. I've also dealt with leaks at the piston that also results in a soft pedal. Need to remove the brake pads and carefully inspect for any signs of wetness.

Audipwr1

You guys think leak over booster? Debating where next to spend money on this

gracer7-rx7

iTrader: (16)

doubt it... booster holds vacuum. there's troubleshooting steps to it somewhere that you can do before firing the $$$ bazooka at it.

Narfle

iTrader: (16)

I'd double check all the lines and bleeders. Could be a bad master cylinder. I'd check the slave cylinder and clutch lines too. Are you losing fluid? If you have that little feel, I'd expect you to be losing fluid visibly or have a bad master cylinder.

billyboy

Booster going out would give hard pedal - more likely to get a master failing and leaking into a booster. Assume pressure tested crimped lines rather than assembled?

I'd try to bleed with a friend to eliminate one variable. Jack stands, fluid, flare nut spanner, tubing and old drink bottle isn't much of an investment if not at hand.

DaveW

We had an issue on my wife's '07 Audi - the Audi dealer service department replaced the fluid and bled the system while it was in for other work, but left it with a low pedal. Turns out their bleeder system had an issue. So they did it a 2nd time, but it still had a somewhat low/soft pedal, so I bled it myself manually. That fixed it.

DaleClark

iTrader: (55)

First off, bleeding brakes just SUCKS. It's more art and luck than science.

The tiniest thing will make a difference in how the pedal feels. One tiny air bubble, a seal in a master cylinder that's a bit worn, old brake lines that are ballooning....all little things that can add up to a difference in feel.

Harbor Freight sells a vacuum brake bleeder that helps out a great deal, you will need an air compressor to run it. Crack the nipple open and let it eat.

The Motive power bleeder that connects to the brake master and pressure bleeds the system works super well.

The old two person pump the pedal and bleed also has its place.

Big one here is bench bleeding the master, if you don't do that you can many times have air in the master that will never get out of there. Hook up lines from the master output ports looped Into the reservoir and pump until no bubbles. Some parts stores have bench bleed kits, they are also on Amazon.

Dale

Audipwr1

Is there a way to adjust the travel of the pedal manually? IE is there an adjustment to the rod that engages the booster?

boostin13b

There should be a lock nut on the rod and you should be able to adjust the engagement similar to the clutch rod. I've had to do this on many cars ive worked on with different swaps, just not on an FD. Be careful though, you need some free play otherwise it will cause the brakes to drag, you will notice this within a couple blocks because it will eventually force you to stop since you cannot completely release brake pressure.

DaveW

Link to my bleed method in VW MK7 GSW forum:
https://www.vwvortex.com/threads/eas...post-113507177

zli944

iTrader: (2)

Recently picked up a Motive power bleeder (the european car fitting works for the FD MC) and it's really great. Since we have the joined res for clutch you get to bleed both!
Having used the compressor powered one, I much prefer the Motive. The compressor power bleeders also works great but the issue is the hose to the bleeder valve doesn't have enough of a nipple to form a perfect and consistent seal. I always end up seeing bubbles in the line so it's hard to tell when the brakes are fully bled. The Motive makes it very much unambiguous and you can do all 4 corners in less than 5 minutes (unless your bleeder valve keeps rounding out like mine, open to suggestions for alternatives, I ordered a pair of brembo bleeders, part # X101739, to try out).

DaleClark

iTrader: (55)

You can get Speedbleeders to replace the bad bleed screw. They are bleed screws with a spring and ball check valve in it so fluid can only go out. It does help with bleeding brakes and works well in a track situation where you may not want to bring a bunch of equipment.

I've had them on my FD for 15+ years and they've been great, no problems.

On the adjustment question, the brake booster has a rod that is adjustable but I've never seen a case where it needed to be messed with. Mazda has a special tool to test it, that's in the shop manual, but I think you can do the same thing with a digital caliper.

I think in this case the first thing is doing a bench bleed of the master. If there is air trapped in the master you can NEVER get it out.

Dale

mecman

iTrader: (11)

I agree with Narfle. Check that the slave cylinder and clutch lines are not leaking either. I also vouch for the Motive Brake bleeder! Works like a charm and allows one person to bleed all the lines quickly. The suggestions to replace the bleeder valves is a cheap thing to eliminate and would go ahead with that on our nearly 30 year old cars.

Audipwr1

Resolved

sadly the shop I was using did a horrible job

the New brake lines weren’t tightened so they were leaking and pulling in air

Upside is the new 929 master cylinder with well installed and bled brakes is epic

great feel and high engagement to match throttle pedal

DaleClark

iTrader: (55)

Glad you got it sorted out and Thanks for posting the resolution!

Dale