william_b_noble

first - you no longer have a stock brake system, all bets are off
second, the power booster is the source of the original spongy feel, it is designed that way, you may be able to adjust the servo in the booster or maybe the vacuum to the booster is weak, or maybe the pedal linkage to the booster isn't quite right - did you check all those adjustments?

Reimu

No, the pedal didn't feel like it used to and felt different from other 944s when it was stock.
The booster doesn't leak or anything after I replaced the leaking one, I'm not really sure if it could work "too well" and cause a pedal to be too soft.

Not to mention that wouldn't explain being unable to lock my tires when I had the stock brakes.
I have adjusted the pedal but haven't messed with anything inside the booster.

theedge

Random thought, do you have a cracked firewall? Have someone watch the booster area for movement while you push on the pedal.

Reimu

It flexes slightly but nothing outrageous. I didn't see any cracks when I had the booster off last year.

When the car is off I can press the pedal about 1 3/4" before it feels solid. Can you block off stainless lines with a tool or is that dangerous? Also I doubt it but would the fact my booster is from a 968 be a problem?

In hindsight I should have done it when I had the old rubber lines but I figured since everything was getting replaced/upgraded surely I would knock out whatever the problem is. You'd think by now I'd learn with my luck.

austin944

I've done that; not sure if it's dangerous. I took a pipe plug from a hardware store and wrapped the threads with a small amount of teflon tape and screwed it into the brake master cylinder outlets, one at a time. I could get a hard pedal by blocking the line to the front driver's side caliper, but I never found the cause.

Pic of plug:
https://rennlist.com/forums/2269904-post9.html

I wound up driving the car and after a while the problem went away for the most part. It could have been trapped air. I had a power-bleeder and must have bled a few gallons through that thing. It's still not rock hard, but it's good enough.

Reimu

Blocked the lines
With the driver's side front blocked it feels great. Got a new caliper hoping it was a bad reman and juggled it around in all directions while bleeding. Stuck it in and it feels exactly the same as the old one.

I really don't get it. I bleed until I have nothing but clear fluid for several minutes. The driver's front is the shortest line and there are no signs of anything weird.

austin944

That's exactly what happened to me! Can you drive the car a bit and see if it gets better?

mytrplseven

I'm a bit puzzled here. Did you ever change the rubber brake lines with stainless braided lines? After the failure to correct your problem by bleeding the system, I would suggest going to new braided lines. I did that on my car along with new pads and rotors and after a complete flushing, my brakes are solid.

Reimu

I really have no other choice. I have changed everything but the hard lines.

I'll summarize it
1)My car blew up and sat for 3 years waiting to be fixed
2)Fix it up and the brakes are extremely hard and don't like stopping
3)Replace booster with used 968 unit, bleed lines, and machine front rotors
4)Pedal now low and soft, can't lock brakes
5)Bleed brakes several more times using the pump method, gravity bleeding, pressure bleeding, pressure+pump bleeding, moving the calipers around while bleeding, etc
6)Replace master cylinder with different make and repeat (while bench bleeding)
7)Put in new pads, no change
8)Gave up and drove for a year after my 10th bleed with no bubbles appearing
9)Installed new big brake front calipers, caliper adapters, 951 rear calipers, stainless lines, rotors, ate fluid, a big 25mm master, r4s pads, and a bias valve. Even replaced wheel bearings.
10) After bleeding several times with the bias valve all the way open via the different methods the pedal still feels pretty much the same as it has since last year
11) Pedal travels around 2.5" before stopping and the front brakes won't lock while the rears will, I have to adjust the valve down to get them to not lock. It does the same with the car off. Also pumping the brakes with the car driving does not firm up the pedal.
12) Block off port going to driver's side caliper on the master and pedal is hard
13) Depress pedal with a stick and leave it overnight and the fluid level won't change
14) Caliper pistons don't move until I have went through the couple inches of dead play and by the time they begin to extend it isn't by much

I've exhausted everything I've read to do online. I've driven with the new brakes as is for over a month and they haven't improved on their own at all no matter how hard I am on them.