[ausgeflippt951]

Originally Posted by Fairfax 944

One other question: Do you have a brake pressure transducer in your system to measure brake pressure for a data logger? If so, you need to be careful to make sure the air is out of the system at the point the transducer connects to the brake lines.

Good question, but no I don't. Maybe someday.

[ausgeflippt951]

Originally Posted by VaSteve

Check for firewall cracks as well.

Firewall cracks? On a Porsche? Zees never heppenz! Eet ees Echte Deutsche Qualitaet!

[Elfer]

Get a 996. Problem solved.

[ruffyz]

Originally Posted by Elfer

Get a 996. Problem solved.

[Vicegrip]

Air can be tested for by doing one hard brake to see what the pedal drop is and then doing a hard stab followed by a hard brake. the stab compresses any air in the system and the hard press after to measure if the pedal still drops the same distance. I found that air makes for a longer pedal and poor bias across the MC more than less torque. (if the pedal is not too long) Fresh rebuilt calipers can act like air in the system too.

The issue might be a moving one. That is to say it was first caused by one thing. but while fixing one thing another issue might have been introduced. Got the air out but installed fresh seals.

It is a long shot but one thing that can makes for a long pedal and soft feel can be new caliper seals. I like to preload the pads when I install on rebuilt binders. One pad at a time remove the pad push the brake pedal just enough to move the piston in so the pad no longer fits. Now push the piston back using the pad and wiggle it in with some friction from the piston. The pad should be held against the rotor by the piston with no wiggle. Repeat for all pads all corners. Makes for a harder pedal after a fresh rebuild. fresh seals pull the pistons back too far and the MC has to make up the gap before clamping onto the rotor.

Are all the wheel bearings good and adjusted to remove any slop? A loose bearing can cause pad kickback. I am thinking air, pad pullback or pad kick back. Air and seal pull back can be repeated without driving. kickback only while driving.

EDIT I should have just read Fairfax 944s post and saved myself some typing.

[HoodPin]

Is the car ABS? You may have to retain the services of someone with the proper diagnostic tool to properly/fully bleed the fluid through the ABS system.

Also, do a long, patient bleed, perhaps even using different fluid (like ATE Blue "off road" to insure you've moved all the old fluid out of the system. In our Boxster, I discovered a troublesome bubble that finally evacuated after a long bleeding session. I'm guessing the bubble was trapped in the line somewhere, and even though I had done a quick bleed of the calipers, the bubble never made it out, and was possibly even rising back up the line afterwards. A long bleed may help move it all the way to the caliper.

You may also want to try enlisting a 2nd person to pump the pedal and hold, after which you open caliper bleed nipple. Then close it, before they raise the pedal and pump again. Not as easy as the Motive method, but it does seem to move a lot of fluid quickly. Just make sure to keep the reservoir topped.

[hobiecat]

Originally Posted by ausgeflippt951

I did bench bleed the MC before installing, but I suppose I could re-bleed it. Nothing I like more!

As an extra data point, what was the procedure you used to really bleed it right? I could be doing it wrong (always a possibility).


So, sounds like the consensus is that it's likely not the Booster.

MC would be my first guess. I know it's no fun to bench bleed it, but.....

Also I can't remember for sure, but isn't there an adjustment on the brake pedal? when you press on the brake, there's a rod that pushes the piston in the MC to push the fluid to the calipers. Could that rod need adjustment?

Actually...just found it. There is an adjustment procedure to set the pedal travel in the service manual....in the Chassis section, chapter 46-5. I found references to it here:

http://forums.rennlist.com/rennforum...al-travel.html

Might be worth a try before pulling out the MC.

[roundel]

Originally Posted by HoodPin

You may also want to try enlisting a 2nd person to pump the pedal and hold, after which you open caliper bleed nipple. Then close it, before they raise the pedal and pump again. Not as easy as the Motive method, but it does seem to move a lot of fluid quickly. Just make sure to keep the reservoir topped.

This. I resort back to this method and have fewer issues than with the Motive route. I am just simple like that. This is what I meant by the Old Skool method.

[BMAN]

Could be the new MC you put in wasn't good. I changed ours twice and the 2nd one firmed the pedal up dramatically. Returned the defective to Porsche, they tested and gave me credit......8 months later.

[Nerfbar]

I've gone to a combo of pressurizing with Motive and then also pumping the brake pedal when I do a complete flush, as suggested by others on Dorki. The result is the hardest pedal I've ever had.