Brakes STILL don't feel quite right.... what is wrong?

[chrisbruck]

I can't for the life of me get a really firm brake pedal on my Carrera. Brakes work fine and have no leaks, just have a little too much squish in them. Maybe they are normal and my buddies SC brakes are just that much better. I expect the Porsche feel to be a lot firmer.

Here's what I've done:
- Replaced the master cylinder, reservoir, and rubber brakes lines with new from our host.
- Rebuilt the calipers myself with new seals and boots.
- Bench bled the MC, but may not have done it correctly. Basically filled the two intake ports from the reservior with fluid and pushed the actuator till it sprayed in my eyes.
- Put it all back together (with no leaks and all bleeders UP!).
- Installed new Textar stock pads front and rear.
- Bled the bejesus out of it with both a Motive bleeder and two man method. Banged on the calipers to work the bubbles out.
- Put the old thin pads back in and "exercised" the caliper pistons to get the new seals to seat better.
- Driven at least 1000 miles on it since putting it all back together.
- Did I say I bled the bejesus out of it numerous different times? Haven't seen any bubbles come out for quite a while.

So what else could I do? Could I possibly have air still in the MC? Any other places air likes to hang out in the system?

Very frustrating....

[rusnak]

This is the secret pedal bleed system, to be admitted to doing only among friends.

Place a block or a brick under the brake pedal. Have a helper pump the pedal fast 10 times, and hold it down hard. The reason is to open the brake proportioning valve. Open and shut the bleed screw very quickly, so as to not let the pedal hit the floorboard. You'll see tons of air go shooting out the bleed screw. Make sure that your bleed hose is well attached to the screw, and that brake fluid goes into a container. Repeat a few times for each wheel. You'll only use a small amount of brake fluid.

[mnez]

Could it be just how the pads feel? Have you used Textar before?
Looks like you've done everything right.

[chrisbruck]

Did the two man method this past weekend.... no bubbles. May not have done exactly as described. Is the proportion valve a bubble magnet?

[petrolblue83911]

when set up properly the carerra brakes are like the hand of G*D.

if they don't feel super responsive and stop the car with authority then something is wrong. Sounds like air in the lines, I've had good luck with the motive speed bleeder pump, and used it post replacing the MC on my 83, and on a 914 years ago. I liked it because I could pump it up, and sit there and watch the bubbles till it was clean fluid.

[chrisbruck]

Yeah, I think my next step is too fill my Motive Bleed FULL of fluid, connect it all up (pinch off the overflow of course), and just let bleed all day while I enjoy a cold one.

Normally I just use the Motive dry to create air pressure and check / top off the reservoir as needed.

[500_19B]

Originally Posted by rusnak

This is the secret pedal bleed system, to be admitted to doing only among friends.

Place a block or a brick under the brake pedal. Have a helper pump the pedal fast 10 times, and hold it down hard. The reason is to open the brake proportioning valve. Open and shut the bleed screw very quickly, so as to not let the pedal hit the floorboard. You'll see tons of air go shooting out the bleed screw. Make sure that your bleed hose is well attached to the screw, and that brake fluid goes into a container. Repeat a few times for each wheel. You'll only use a small amount of brake fluid.

Hey Rusnak, can you explain the function of the block under the pedal during this procedure. It sounds like your intention is for the person sitting behind the wheel to exercise the pedal and then hold it, whilst you very briefly open the bleed screw, with the intention for the pedal not to go to the floor... Is the block just a back up in case one is not quick enough (trading off the chance of air sucking back in over the possible issues of pushing the MC seals past their normal working zone?)

[rusnak]

Yes, the block is to prevent the pedal from going clear to the floor. Don't let the pedal person let up on the pedal until you've closed the bleed screw. This method will bleed the last remaining air when the Motive has failed.

[500_19B]

Thanks Rusnak!

I have a feeling mine are still a touch soft too. Like the OP, I have new everthing, and I have done all the same steps too. I will try this as well.

[porschenut]

In that case, I'm confused by your statement:

Originally Posted by rusnak

Open and shut the bleed screw very quickly, so as to not let the pedal hit the floorboard.

If the block is there to prevent the pedal from going to the floor, then why do you need to be quick on the bleed valve?

[DRACO A5OG]

I read you stated there is no leak, but did you check the T connections behind the stone guard?

Mine were bled as known to man kind only to discover my T connection for the rear brakes were weeping. Soft pedal found

[chrisbruck]

Originally Posted by DRACO A5OG

I read you stated there is no leak, but did you check the T connections behind the stone guard?

Mine were bled as known to man kind only to discover my T connection for the rear brakes were weeping. Soft pedal found

I'll check that tomorrow but the fluid level has never dropped.

New issue today.... while stopped twice on two separate occasions, the pedal slowly but surely dropped to the floor. Pumped it back to fine and under normal driving it never happened, only when stopped. No obvious leaks. Is this is sign my "new" master cylinder is kaput?

[chrisbruck]

And where exactly is this stone guard and T connection?

[ganun]

For sure

[ganun]

In my years of doing cars once I had a new aftermarket BMC come back after about a week. Upon disassembly it was full of the metal particles from manufacturing.

[rusnak]

Originally Posted by chrisbruck

I'll check that tomorrow but the fluid level has never dropped.

New issue today.... while stopped twice on two separate occasions, the pedal slowly but surely dropped to the floor. Pumped it back to fine and under normal driving it never happened, only when stopped. No obvious leaks. Is this is sign my "new" master cylinder is kaput?

That sure doesn't sound good. This is the reason for the block under the pedal. It's so that you don't forget to stop before pushing the pedal to the floor.

[LJ851]

On motorcycles that refuse to get a nice firm lever, i zip tie the brakes "on" pretty hard and leave it overnight. In the morning i grab the lever ,cut the zip ties, and slowly release the lever. It always improves the firmness and sometimes the difference is amazing.

Find a way to hold the brake pedal down hard and leave it overnight, i bet it will help.

[Ronnie's.930]

Not a Porsche, but for many years, I had a very difficult time getting a consistently firm pedal on an E350 box truck I own. I knew I had air in the MANY feet of lines and maybe the rear, anti-lock cylinder, but two-man, vacuum "sucking" pump, and gravity never worked right. I then read a tip on the 930 forum that described taking a spare master resv cap, fitting a hose barb to it, attaching a proper sized length of hose between the barb and an air gun, and then to use about 20-25 psi air pressure to force the fluid through, and air out of, the system. After about 15 minutes of doing this (stopping to add fluid several times, of course) I had the best pedal feel I had experienced in that thing in over ten years. I now use this method on all cars, trucks and motorcycles I work on.

[chrisbruck]

The new plan is to bleed on more time with the Motive filled with fluid at 20 psi for a long duration and see what happens. If still sketchy then I'm just going to pony up and take it my local Porsche race shop and have them check it out before I tackle the MC again myself. $500 for them to fix it is a whole lot cheaper than bent up sheet metal.

Just frustrating that something so supposedly simple as refreshing the brakes is being such a PITA.

[theiceman]

not to state the absolutely obvious but is there any possible way you could have put any of the calipers on upside down with the bleed nipple at the bottom ?