Yup! been there, thought that, done that! I bled and bled and bled until I swore and swore and ordered a MC. Then i filled it, bled it like a normal person and drove away.

Quote:

Finally one last question. I think I will replace the master cylinder in the name of preventative maintenance. Green912 was talking about pre-priming the master cylinder. Guess what? Bentley doesn't say anything about doing that... so now what do I have to do to not screw that up? This is ridiculous! I've bled brakes and clutch systems so many times in my life... what the hell?! Thanks guys!

I didn't prefill mine, but it wasn't too bad to bleed. But Getting a little fluid in there might make it easier.

I don't think you should replace the master cylinder yet. It's most likely your bleeding is not driving the air out of the system. You've pushed the padel all the way to the bottom. Some said it will damage the seal. If you actually opend up a master cylinder and take a look at the rubber piston, you will know the rubber piston can not be damaged just by pushing to futher in the cylinder. If the seal is really shot, you give a hard pump, it will stay, if you slowly apply the pressure, it will sink to the bottom of the floor. Be patient, don't jump to the conlusion right away. You can even toll the Porsche to the nearest Porsche specialist to have them bleed the brake for you. It's cheaper to go for the master cylinder replacement.

I just had to thank you, Mr Green 912
That little tid bit saved my butt. I'll post what happened to me, since it's inevitable that this will happen to someone else.

I changed the o-rings in my front calipers since one of them was dragging a little and producing a "hummm" like Jim Carey in Ace Ventura Pet Detective. Anyway, after I put everything back together and bled them with the Motive bleeder, and then re-bleeding the brakes, and re-bleeding etc etc. I was at my wit's end. Then the after reading a half dozen threads, bingo. A cheap piece of wood, and a cheap brake pad spreader to re-position the brake cylinder. Problem solved, time to go have a beer!

you know a common occurance is to mix the left and right calipers up and installing them backwards , the bleeder needs to be at the top of the caliper or you'll NEVER EVER EVER get all the air out.....ask me how i know :D

Question regarding brakes. I just had my rear brakes redone, pads and rotors and there is an ear-splitting squeal when I apply the brakes. It is really annoying. Any thoughts? Thanks, I am a poor damsel in distress at the mercy of the mechanics.

I'me only guessing, but, pad squeal is usually caused from uneven wear to the rotor.
The pads move slightly when the brake pedal is applied causing the noise.
Simple remedy is to machine the disc rotor.
As you have new pads & rotors, i guess again this is not the cause.
Sounds like a warranty job.

Brakes from hell!!!
 

Had the exact same thing happen about 3 months ago, doing a brake job noticed a bat seal on front caliber. Rebuilt two front ones, went to bleed same thing. I had to go through the process at least 20 times. Tap on the calipers with a small hammer to get excess air out.
You will be amazed how much air is still in there I thought for sure it was the MC.
Let the car settle for a few days went through process again, tapping on the calipers more air bubbles.
It eventually all came out, Pelican has a good article on testing your MC.

If the pistons were removed during the rebuild they have a notch that has to be in a certain orientation to help prevent noise. If they were not assembled correctly this could be your problem. They may have also used a harder track pad that could make noise until hot.

Does anyone have a template that they could post for the 20 degree angle for the brake pistons?

I'm thinking about making my own ATE brake piston gauge. I can't seem to find one online for sale.

Take a square (1 nice 90 degree angle) piece of cardboard and draw a mark 3 inches down one leg from the 90 deg corner. Down the other leg draw a mark 8.25 inches away from the corner. Draw a line between them and that is 20 degrees (19.98). Cut to size you need.

I didn't read all the responses, so I'm sorry if this advice repeats others.

Sometimes, after a caliper rebuild, our cars show more pedal travel than we like. No sponginess, just longer pedal travel. This is due to the pistons not yet being seated in their ideal spot. A couple of hundred miles of driving fixes this. Or....remove each pad one at a time, tap the pedal slightly and pound the pad back between the piston and rotor. This eliminates the gap.

Sponginess is air in the system.

Sometimes a MC acts like this: When you jam on the brakes, everything works fine. If you press on the pedal gently and slowly, it will go to the floor. If you press quickly and firmly, the pedal is firm.....but if you back off just a tad and then press gently and slowly, tyhe pedal will go to the floor. In this instance, the seal in the MC is allowing fluid to pass by, except when sudden pressure is applied in which case the fluid pressure presses the seal up against the piston and makes it work, even though it is worn. Time for MC seals, or a new MC.