mzman

Last week when I was driving around my brake pedal suddenly went very soft, usually there is hardly any pedal movement to apply the brakes, now there is a inch or so of squish before it starts to brake. Not only that but it happens randomly, I can be driving and the pedal is nice and firm then one stop its really soft, then after 10 or 15 mins its back to firm. I am guessing that I have a air bubble in the line? I just want to know how it got there, the brake fluid was always between min and max. And what is the best way to fix it? Will it work its self out? I have limited tools here at school.

Scootin159

do you have access to a 7mm and 8mm box wrench? If so, bleed the brakes. If you can get under the car, you can even do it without removing a wheel... although it is easier to do (and cleaner) when you do it with the wheels off.

It's an easy process, but just be careful if you're jacking the car up & clean up any spilled brake fluid (stuff eats paint like nobody's business).

mzman

Ya, I have those wrenches, but last time I bled the brakes on my NA it made the pedal soft and no matter how much I bled them it never went back to the firm pedal, and I don't want to make it that way all the time on my turbo.

When I was bleeding them on the NA back home I used my motive pressure power bleeder thing because the basic way just sucked air into my clutch.

My pads are due for a change they have started squealing pretty bad not to long ago, could the worn pads have anything to do with it?

austin944

Sounds like a similar problem as described in this thread:
https://rennlist.com/forums/924-931-944-951-968-forum/324700-brake-question.html

Do you mean that the brake pedal travel is greater than normal and once it starts braking then the pedal becomes hard (indicating the above problem), or do you mean the pedal is soft even after it goes through its travel and it starts braking (which might indicate air in the lines)?

DarylJ

If it's not what austin944 pointed to, it could also be a master cylinder. Put your foot on the brakes slowly/lightly when the car is running. If it pedal keep sinking, it's probably the seals in the master. Usually if you stab at the brakes they feel fine.

renvagn

If your pads are that worn and your driving the car hard and not braking with proper technique, you could have boiled your fliud. Porsche brakes are one of the true highlights of these cars. Get new pads, check the master, do a motive bleed with and assistant on the brake pedal and push new fluid through the system. Good luck.

mzman

Yes, it has lots of travel then goes hard. Then sometimes its hard right from the beginning so there is almost no pedal movement required to stop the car.

All seemingly random times, not just around corners, going down the interstate I get different lengths of pedal travel.

Today I will try stabbing at the brakes to see if its the master.

austin944

Sounds like the 'knockback' problem described in the link I posted. Try the wheel bearing looseness test in that thread.

mzman

Going around corners had no effect, and pumping the brakes once doesn't fix the problem, it will stay soft for 10 stops on the interstate, then all of a sudden it goes back to normal, all in the time span of 10 mins.

It is hard to tell but it seems like stabbing at the brakes when idle works fine, but when i slowly push it sinks in.

I will try the wheel bearing looseness test today.

DarylJ

Master cylinder. Classic symptom. I would bleed your brakes first just to be sure. And by bleed I mean complete fluid change. Get a motive or other power bleeder to do this if you don't have one. You'll need it to keep your sanity when you have to change the master anyway.