Soft brake pedal - What to try next?
05-20-2017, 07:28 PM
#1
Racer
Thread Starter
Soft brake pedal - What to try next?
I would love some help with what to do next for solving a long brake pedal.
Car: 1992 stock 968 with about 95,xxx miles. with ABS.
Repairs so far:
Attempt #1: The rotors were very scored and the drill holes had cracks, so I replaced rotors with new and pads with PF97 race compound pads. In doing so, one pad had been stuck in the rear passenger side caliper so badly that I had to remove the caliper completely to get the pad out. So I fully bleed the system the old fashion way without a power bleeder, but rather using my 12 year old to pump the pedal. I thought everything seemed in good order, but when I took it for a test drive the brake pedal was really long. Almost to the floor long. Scary long and it hadn't been like that before.
Attempt #2: I found that the paint was peeling off the booster below the master cylinder and found the master to be leaking. Looks like an old leak that may have been gradual, but was now pretty bad. I replaced the master cylinder as well as the hose to the master clutch cylinder as the hose that was there was the wrong type of hose. Again, I belled the system, this time with a power bleeder. I also belled the clutch which I did reverse bleed from the bottom.
I do not see any leaks anymore. when the car is turned off the pedal feel a little long on the first pump and hardens right up by the 3rd pump, which seems pretty normal. BUT when the car is running, the pedal is long. Not quite as bad as before fixing the leak, but still long.
I'm using ATE Type 200 and PF97 pads. PF 97s usually feel pretty hard and quick to catch. Any ideas? Could there still be bubbles somewhere? Could air get into the ABS system and be causing this? I Should I try another bleeding method?
I look forward to some great answers!!
Thanks,
John
Car: 1992 stock 968 with about 95,xxx miles. with ABS.
Repairs so far:
Attempt #1: The rotors were very scored and the drill holes had cracks, so I replaced rotors with new and pads with PF97 race compound pads. In doing so, one pad had been stuck in the rear passenger side caliper so badly that I had to remove the caliper completely to get the pad out. So I fully bleed the system the old fashion way without a power bleeder, but rather using my 12 year old to pump the pedal. I thought everything seemed in good order, but when I took it for a test drive the brake pedal was really long. Almost to the floor long. Scary long and it hadn't been like that before.
Attempt #2: I found that the paint was peeling off the booster below the master cylinder and found the master to be leaking. Looks like an old leak that may have been gradual, but was now pretty bad. I replaced the master cylinder as well as the hose to the master clutch cylinder as the hose that was there was the wrong type of hose. Again, I belled the system, this time with a power bleeder. I also belled the clutch which I did reverse bleed from the bottom.
I do not see any leaks anymore. when the car is turned off the pedal feel a little long on the first pump and hardens right up by the 3rd pump, which seems pretty normal. BUT when the car is running, the pedal is long. Not quite as bad as before fixing the leak, but still long.
I'm using ATE Type 200 and PF97 pads. PF 97s usually feel pretty hard and quick to catch. Any ideas? Could there still be bubbles somewhere? Could air get into the ABS system and be causing this? I Should I try another bleeding method?
I look forward to some great answers!!
Thanks,
John
05-20-2017, 10:44 PM
#2
Nordschleife Master
I take it that the master will hold pressure once you press it down.
I'll suggest more bleeding. Once you open a brake line it'll take a while to get all the air out.
"Press..."
"Hold..."
"Release..."
brings a family together.
I'll suggest more bleeding. Once you open a brake line it'll take a while to get all the air out.
"Press..."
"Hold..."
"Release..."
brings a family together.
Last edited by GlenL; 05-21-2017 at 11:39 AM.
05-21-2017, 10:47 AM
#3
Addict
Rennlist Member
Rennlist Member
The motorcycle trick of leaving the system under pressure really helps also. It takes a while in the 968 with all those bleeders but it can chase out some bubbles that are hidden really well.
I use a couple scrap 2x4s to pin the brake pedal down using the front seat. Leave it sit for a few hours, then open one bleed screw, then close it. Then lift the pedal, brace it back down again, and repeat for a couple days. I bleed inboard then outboard because if there is air in the caliper I do not want to move it around from inboard to outboard.
Obviously a pressure bleeder helps. If you did not bench bleed the MC it may also be hard to get the system free of air also.
I use a couple scrap 2x4s to pin the brake pedal down using the front seat. Leave it sit for a few hours, then open one bleed screw, then close it. Then lift the pedal, brace it back down again, and repeat for a couple days. I bleed inboard then outboard because if there is air in the caliper I do not want to move it around from inboard to outboard.
Obviously a pressure bleeder helps. If you did not bench bleed the MC it may also be hard to get the system free of air also.
05-21-2017, 01:19 PM
#5
Racer
Thread Starter
Thank you so much for your feedback so far! You all say bleeding, with some various techniques.
On the idea of leaving the brakes under pressure using the pedal and a 2x4: Can you just leave a power bleeder on it for a long period of time and accomplish the same thing?
Any comments on reverse bleeding. That's the way I tend to bleed the clutch as no other way works well, but I've found some threads that recommend reverse bleeding the brakes.
On the idea of leaving the brakes under pressure using the pedal and a 2x4: Can you just leave a power bleeder on it for a long period of time and accomplish the same thing?
Any comments on reverse bleeding. That's the way I tend to bleed the clutch as no other way works well, but I've found some threads that recommend reverse bleeding the brakes.
05-21-2017, 07:56 PM
#6
Chainsaw
Rennlist Member
Rennlist Member
Are you using the ATE 200 Gold fluid? If not use the colored fluid in the next bleeding. Start with R rear (furthest away from MC) and nleed until fluid changes to gold.
I am no expert but I have successfully used this process before.
Have Power Slot Cryo rotors on all four with Hawk HP Plus pads.
I am no expert but I have successfully used this process before.
Have Power Slot Cryo rotors on all four with Hawk HP Plus pads.
05-21-2017, 09:42 PM
#7
Racer
Thread Starter
UPDATE - RESOLVED!
Thanks for the help. First off, I had filled the master cylinder with fluid prior to installation as outlined in the clark's garage procedure. I just use ATE 200 - I've heard a lot of mixed things about the blue brake fluid, enough that I stay away from it.
To finally rectify the soft pedal I did two things. I put on a power bleeder and set it to 15 lbs of pressure and left it for 3 hours. I'm not sure if that did anything. I then bleed again, using the power bleeder, but this time started on the "inside" bleeder of each caliper. Usually I just bleed from the outside bleeder. I use a clear bleeder hose so I could see what was coming out and for BOTH rear calipers there was certainly air bubbles stuck right near the bleeder valve. Absolutely no air come out at another valve in the entire process.
Result is the brakes feel normal and responsive.
Thanks for all your help!
Thanks for the help. First off, I had filled the master cylinder with fluid prior to installation as outlined in the clark's garage procedure. I just use ATE 200 - I've heard a lot of mixed things about the blue brake fluid, enough that I stay away from it.
To finally rectify the soft pedal I did two things. I put on a power bleeder and set it to 15 lbs of pressure and left it for 3 hours. I'm not sure if that did anything. I then bleed again, using the power bleeder, but this time started on the "inside" bleeder of each caliper. Usually I just bleed from the outside bleeder. I use a clear bleeder hose so I could see what was coming out and for BOTH rear calipers there was certainly air bubbles stuck right near the bleeder valve. Absolutely no air come out at another valve in the entire process.
Result is the brakes feel normal and responsive.
Thanks for all your help!
Trending Topics
05-22-2017, 07:36 AM
#8
Addict
Rennlist Member
Rennlist Member
Pinning the brake pedal down is much much higher pressure than the power bleeder can safely produce so it's not the same as having a pressure bleeder hooked up for some time. I think the idea is to make the bubbles a lot smaller by compressing them and then they can be shot downstream or work their way back up to the MC a lot more easily. I have used this technique to get an OK pedal up to Porsche standards.
However if you had not bled the inner calipers that is a spot that traps air (hence the bleeder). If you let no air into the system like if you are changing the brake fluid with a pressure bleeder you might get away with just bleeding outboard though.
-Joel.
However if you had not bled the inner calipers that is a spot that traps air (hence the bleeder). If you let no air into the system like if you are changing the brake fluid with a pressure bleeder you might get away with just bleeding outboard though.
-Joel.
05-22-2017, 07:39 AM
#9
Chainsaw
Rennlist Member
Rennlist Member
I was going to recommend the ATE Super Blue instead of the Gold but the Blue is now illegal in the U.S.
http://hooniverse.com/2013/08/16/bra...-distribution/
They should make brake fluid flourescent orange! This would make it easy to see at the track or at home if fluid on the parking pad is brake fluid.
Last night, [2013] we heard through the grapevine that Alfred Teves Enginieering (ATE, a division of Continental) would be discontinuing the sales and distribution of the popular “Super Blue” variant of its DOT 4 brake fluid. Apparently the Super Blue fluid has run afoul of the Federal Motor Vehicle Safety Standard after nearly 15 years on the market for being blue. For the correspondence Continental sent to their distributors, and more of the story, click through the break.
It seems that the federal government has taken 15 years to figure out that Super Blue fluid is, in fact, blue in color. Evidently there is a stipulation that all brake fluids distributed in the US must be either clear or amber in color. This begs the question, why is that a law? The blue color was one of the major selling points of Super Blue fluid, as it made a complete bleed of your braking system much easier to accomplish. I would use ATE Super Blue and ATE Typ 200 fluids alternately (Typ 200 is the amber version of Super Blue), filling the master cylinder with one color, and when the color coming out through the caliper changed, it was easy to tell that all of the old fluid had been expunged from the system.
As this is effective immediately, the supply line for this brake fluid has already dried up. That said, there are likely some retail establishments that will continue to have it on their shelves until it is sold out, and some of those retailers will likely continue importing Super Blue under the auspices of “For Off-Highway Use Only”, but we’ll see.
It seems that the federal government has taken 15 years to figure out that Super Blue fluid is, in fact, blue in color. Evidently there is a stipulation that all brake fluids distributed in the US must be either clear or amber in color. This begs the question, why is that a law? The blue color was one of the major selling points of Super Blue fluid, as it made a complete bleed of your braking system much easier to accomplish. I would use ATE Super Blue and ATE Typ 200 fluids alternately (Typ 200 is the amber version of Super Blue), filling the master cylinder with one color, and when the color coming out through the caliper changed, it was easy to tell that all of the old fluid had been expunged from the system.
As this is effective immediately, the supply line for this brake fluid has already dried up. That said, there are likely some retail establishments that will continue to have it on their shelves until it is sold out, and some of those retailers will likely continue importing Super Blue under the auspices of “For Off-Highway Use Only”, but we’ll see.
They should make brake fluid flourescent orange! This would make it easy to see at the track or at home if fluid on the parking pad is brake fluid.
10-01-2023, 01:27 PM
#10
