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Soft Brake Pedal in C2

 
Old 06-12-2004, 09:54 PM
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90C2_Cab
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Default Soft Brake Pedal in C2

I recently did some suspension work replacing springs and shocks, flexible brake lines, brake pads, brake fluid etc.. The brake fluid being replaced looked pretty old, it was black and nasty. When finished bleeding the brakes(three rounds) starting with quick fill reservoir, RR-LR-RF-LF using a power bleeder(@ 30 psi) and 2 liters of ATE super blue and no evidence of bubbles in the fluid the pedal is still real soft, pump it three times and it firms up hard. Release for 3 seconds SOFT.

The Porsche manual describes actuating the pedal full travel while bleeding, which I did. From reading the forums this is not something that should have been done. Whoops

Also, from what Ive been reading I'm not really sure what to bet on, the system still has air in it (which I doubt), ABS system has air, a local porsche service guy says the master cylinder is the problem. Not wanting to replace such an expensive item without more facts I wanted to get a consensus form you folks.

--Eric
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Old 06-12-2004, 11:57 PM
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Default a possibility...

I read a post from somewhere (I think it was Pelican) where a dude forgot to bleed BOTH bleeder screws on each caliper - only did the outer ones. Just making sure....


If you did get all 8 bleeder screws (your rears may only have one - not sure on those smaller calipers), I'd pump the pedal a few times, or even go for a drive, then re-do the process. That should do it.

Good luck.
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Old 06-13-2004, 12:36 AM
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Default Followed procedures

the fronts have 2 bleed screws(bled both, outer then inner) rears have 1. Using the pressure bleeder is supposed to eliminate the need for a second person to pump the brakes, correct? Or, would it help to pump the brake firm and use the pressure bleeder and follow the bleeding order? I don't want to replace the master cylinder! NO! NO! NO!
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Old 06-13-2004, 09:52 AM
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When you replaced your pads, did you push the pistons back into the caliper? If yes, until the pistons wiggle their way back out to be in proper contact with the pads, you can have the symptoms you've described. You can try keeping pressure on the brake pedal, let up, pressure, let up, etc to move the pistons out, or regular driving will do the same thing.

If you want to be sure you're not having master cylinder problems, pump it up to where it's hard hard, then push hard on it - if it slowly sinks to the floor you need a new master cylinder.
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Old 06-13-2004, 02:06 PM
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Originally posted by Bill Gregory

If you want to be sure you're not having master cylinder problems, pump it up to where it's hard hard, then push hard on it - if it slowly sinks to the floor you need a new master cylinder.
Excellent advice Bill!! I'll have to remember that one some day down the line.
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Old 06-13-2004, 02:12 PM
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The car has been driven, so, the pads are fully in contact with the rotors. the pedal does get hard after 3 quick pumps and stays there, it does not sink to the floor or move at all once its pumped up. I'll have a friend pump the brake hard and attempt another bleeding round I guess. Thanks for the input! keep it comming.

--Eric
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Old 06-13-2004, 02:42 PM
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The car has been driven
It can take up to 100 to 125 miles of driving to seat the pistons, depending on how far they were pushed in.
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Old 06-14-2004, 11:40 AM
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I found the answer to the "Soft" pedal. When the calipers were off the car I re-installed the rears thinking they were interchangeable, which they are sort of. When they were mounted the bleeder valve was BELOW the piston, a professional mechanic friend of mine noticed the wear was significantly less on the new rear rotors and found the bleeders were not at the top of the caliper! I quickly swapped the rear calipers bled the system and found the pedal to be as hard as I remember it. I had become familiar with the setup and ignored the obvious, whew! I real happy I didn't start buying parts that didn't need replacement.
--Eric
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Old 06-14-2004, 01:50 PM
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Good find!

I forgot to mention that - missing one bleed screw, or mounting them upside down seems to be a common occurrence! Glad you're back together!
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