soft brakes 1st gen

[KK]

Rex,

I am in the same boat and have been since the beginning of last season. I have replaced almost everything! New calipers, MC (<-3), lines, caliper brackets, etc. Enough to drive you insane!

I replaced the booster with another one, but it was from the junkyard. After talking with a fellow racer (pro-7 guy) who had been hunting down the same problem and also replacing EVERYTHING, he found that it was the booster.

My car stops fine as well, but has this long/soft pedal and I hate it!. I am going to replace the booster and perhaps you should try the same.

It is very easy to do. First, unbolt the MC from the booster (undo all lines to master and get the MC out of the engine bay) along with the proportioning valve. Second, pull out the pin that connects the pedal to the pushrod. Then there are 4 nuts that go through the firewall (from outside in), remove them (12 or 14 mil). THe booster is now free and ready to come out. It will have some sealant on it making it a bit tough to break free from the firewall, but it will come off.
Reverse the process and you are done!

Remember to always bench bleed a new MC before installing also.

Hope this helps. For both of us...

[Rex B]

Thanks KK, that's about twhere I was coming up as well. Are you going to order the new unit from Mazda? Wonder if there's a reman unit? I'll check A-1.
Sounds like you are a little ahead of me. If you get that booster on, be sure and let us know if it solves the problem.

[KK]

you're welcome

I won't get it on until after next week, but will keep you informed.

I was going to order the Mazda part. I have had nothing but bad experiences with the reman-parts...

[IT7#66]

We went through the same thing before the season began and found a bad OEM proportioning valve. Also you may have a bad (new) MC.... It happens!

[lee graser]

Lets throw a couple more thoughts into this "soft-pedal" problem------If pads are worn at an angle this will give a "soft--deep " pedal---if the calipers are not 100% parallel to the rotors----this can cause a soft deep pedal (pads touch at an angle before full flat contact)---I have experienced this on a 1st gen 7---

[Rex B]

Okay, so here's the checklist so far:
Leaking master cylinder
-bypassing internally?
Air in lines
-high-temp fluid?
-correct bleeding sequence?
-rebuild calipers?
Flex lines replaced by SS braided?
pads cocked in caliper?
-OE pad clips discarded? not yet
Non-parallel caliper mounting?
-pads wear at an angle
Rotor runout?
Firewall flex?
Booster failure
OE Proportioning valve
Slack in rear e-brake adjustment
-ratchet them manually
MC to-pedal rod adjustment
Pedal height limit adjust

Good suggestions all, thanks for the input. I'll let you know what I find.
BTW, I raced it last weekend before I had a chance to go through all this. Brakes worked fine, but I was getting on the pedal way early due to lack of confidence in the brakes. It stopped fine, the limiting factor was psychological.
Next event is at TMS (first SCCA race there) which will likely be hard on brakes, so I have some work to do.

[Tak]

I have retained the parking brake on my car, and have found the only way to get a firm pedal is to adjust the parking brake per the Mazda manual (adjust until it only clicks 7-8 times pulling the lever). I adjust it every session.

Also be wary of swapping pads inside/outside, as they do wear differently. Keep the pads in the same location. Finally, a warped rotor or sticky slider may result in a spongy pedal. Warped rotor will thump your foot. Sticky slider usually shows as pulling under braking.

Good Luck

Tak
#29 ITA,
SFR