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2002 C2 with the standard calipers. Ever since I got the car, I've always been underwhelmed by the braking performance. It never lived up to the "Amazing Porsche Brakes" that I've heard about. I drove a friend's 997.1 C2S and those brakes were definitely amazing. This sent me on a quest to "fix" my car.
In the pursuit of fixing the issue I've done the following:
Nitto INVO Tires
Changed Pads/Rotors (Cool Carbon Pads, and Carbotech AX6 with Sebro Slotted Fronts and ATE Drilled Rears)
Brake Fluid Flush (ATE Super Blue, Motive Pressure Bleeder)
Goodridge Stainless Steel Braided Lines
Brake Fluid Flush (ATE TYP 200, Motive Pressure Bleeder)
Adjusted Brake Pedal Arm into Booster
Changed Master Cylinder
Brake Fluid Flush (ATE TYP 200, Motive Pressure Bleeder and 2 Person Pumping with Durametric PRO cycling the "booster pump")
Nothing has significantly helped make the car feel "Good". The car does stop, but I feel like it's lacking in stopping power, and the pedal feel leaves a lot to be desired (soft pedal, firms up once you stand on it).
During the 2 Person Pumping today, I noticed that the hardline going into the ABS Distribution block Labeled "V" makes air bubbly/squishy noises when the pedal is depressed. Line in question circled below:
No matter how long I bled the brakes, it seemed impossible to get this squishy sound out of the system. I tried tapping the line in an attempt to "move" the bubble, but that didn't help either.
Is there anything else I have overlooked? There doesn't appear to be any uneven wear on any of the corners, the pedal always comes back up, so I don't suspect the calipers or the booster (although the booster makes wooshy noises when the pedal is depressed and the engine is running).
110k on the calipers- is it time to swap them? All pistons seemed to move freely and dust boots looked fine, although I didn't remove pistons to check for scoring or anything.
The car does have PSM. Is there a special sequence for bleeding the PSM equipped cars?
It's quite possible air got introduced into the system into the components that can only be bled using Durametric/piwis. E.g., replacement of hydraulic/abs components.
Is the car a manual? If so, have you bled the clutch slave cylinder when you flushed ? It is part of the braking line system and can get air trapped.
That should be ok because the clutch has a separate partition/circuit. It shares the fluid in the brake fluid reservoir, only at the very top portion though. The rest is an independent circuit.
110k on the calipers- is it time to swap them? All pistons seemed to move freely and dust boots looked fine, although I didn't remove pistons to check for scoring or anything.
The car does have PSM. Is there a special sequence for bleeding the PSM equipped cars?
Yes, there is an extra step of bleeding the PSM via the booster pulp out the front right caliper while the brake bleeding equipment is hooked up (pressure bleeder). I use a PIWIS1 or 2 to accomplish this, and don't forget the manual calls for pumping the brake pedal fully at least 10 times during this process!
I actually tried bleeding the FR caliper using the durametric last night- both with the pressure bleeder at 15 PSI and via pumping.
I was clicking on "Booster Pump", and when I click "stop", I hear a clicking noise- either the relays or some solenoids I'm guessing, but I never hear any pumping noise. I read somewhere that the pump can be very quiet, but I'm kind of skeptical as to if the durametric is even actuating it. No ABS/PSM faults though, and both of them do work.
I've uploaded a video of the sound near the mc when the brake is depressed. It definitely has air trapped in it, but I have no idea where, and how to get it out. It also sounds like it's coming from the tip of the MC. I don't want to, but perhaps removing it and bench bleeding it might alleviate the issue?
I actually tried bleeding the FR caliper using the durametric last night- both with the pressure bleeder at 15 PSI and via pumping.
I was clicking on "Booster Pump", and when I click "stop", I hear a clicking noise- either the relays or some solenoids I'm guessing, but I never hear any pumping noise. I read somewhere that the pump can be very quiet, but I'm kind of skeptical as to if the durametric is even actuating it. No ABS/PSM faults though, and both of them do work.
I've always been able to hear the pump motor running when I've bled the PSM/ABS system... You might know this though it's unclear from what you wrote above, but the pressure bleeder should be hooked up at 2 bar, and then bleed via the front right bleeder while pedal pumping x10 while the ABS pump is running.
While it's specific to the 996 turbo, this excerpt from the manual might help things in your case before you start undoing what you previously did:
After installing a new brake master cylinder and/or a new hydraulic unit, do the following while bleeding:
• Open the right rear bleeder valves, then fully depress the brake pedal several times.
• Hold for 2 − 3 seconds after each depression, then release slowly.
• Repeat this procedure in the sequence rear left / front right / front left. This will remove all air bubbles
(from the primary circuit).
Thanks for all the suggestions guys! It's all really helpful.
I attempted to bleed the braking system again, following the above method, and again "activating" abs via durametric. I wasn't convinced it was actually making the pump run despite the status bar claiming "command sent successfully".
Had a friend with a 997 come over and ran the abs pump on his car through durametric, and the pump makes a low pitched whining noise.
Since the car does engage abs/psm, and there aren't any fault codes being reported by the abs computer, I can only assume that the durametric is unable to activate the abs pump successfully on my car for some reason.
I found a couple of old threads with people echoing my experience, so it seems like it's an actual issue, and not just a fluke with my car. I'll email durametric and see what they say- hopefully I can get it to work!
Could be the Durametric can't activate your pump, or could be your fluke is the ABS pump doesn't work and you have found the problem with your soft pedal/weak stopping power. Did you check the ABS fuse and relay?
I'm not sure if it or how it matters (the durametric guys would know), but the PIWIS has a separate specific "bleed" function that is not the same as the "drive links" activation of the booster pump which is what you're doing with durametric (at least on your friend's 997).
The support page does show a specific brake bleeding activation for the 997. I wonder if you are in the right place in the software for that.
Maybe contact technical support and ask them.
997 GT3 Master Cylinder and Castrol SRF fluid will improve the feel. I've completely emptied my brake fluid system probably 10x and never once used the durametric to activate the ABS pump.
As for the squishy noises, that doesn't sound right. If you want to try swapping out the ABS I have a spare unit that you can borrow for troubleshooting.
08-27-2017, 03:09 AM
Braking Issue- Soft Pedal/Weak Stopping Power?
