extremely soft pedal

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kevlar28273

New Member

May 23, 2009

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Charlotte, NC

Jan 22, 2012

#1

• Jan 22, 2012

• #1

i have always had poor breaks on my 98 GT. so when it came time to replace them again, i decided it was time for a good upgrade. i replaced them with SSBC 2 pistons front, one in rear. disk size was increased to cobra diameter. now i have very little pedal. i have bled and bled the brakes, no change. i decided (and so did SSBC) that it is still air trapped. i bought a Pheonix Systems (reverse bleeding system). no change. thought it might be the MC so replaced that with a Cobra system (same year). no difference. i can depress the brake pedal about 2 inches until the front calipers are unable to be turned by hand. i am positive its not an air bubble. what else is there? any and all ideas will be greatly appreciated!! thanks

 

ace940

Member

Oct 16, 2011

87

1

17

Jan 22, 2012

#2

• Jan 22, 2012

• #2

brake booster maybe? idk much about brakes and. there isnt much else other than maybe a bad abs relay or something. you could have your abs tested. welcome to the site

 

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kevlar28273

New Member

May 23, 2009

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Charlotte, NC

Jan 22, 2012

#3

• Jan 22, 2012

• #3

THANKS ACE, let me add, i dont have ABS and also that i have great breaks the last inch which is almost to the floor. the first 2+ inches, there is nothing but the last 1/2-1 inch it feels great. i dont dare drive it like this. i just read in my Hayes manual that if the brake booster is bad, then its the opposite condition....... hard brake pedal.

 

bhuff30

Founding Member

Dec 11, 2001

6,037

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129

Olathe KS

Jan 22, 2012

#4

• Jan 22, 2012

• #4

A bad break booster could result in a hard pedal, but not always. When the booster in my 88 went bad, it was similar to what you are describing. Sometimes, the brake pedal would catch at the normal spot, but more often it would nearly get to the floor before I get any real braking. I don't really understand why though. However, keep in mind that was a vacuum booster.. you should have a hydroboost cylinder as I recall.

 

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kevlar28273

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May 23, 2009

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Charlotte, NC

Jan 22, 2012

#5

• Jan 22, 2012

• #5

funny, on the 4 cyl vs your V-8, i experienced this first when i was going on I-40 through the NC mountains when i was driving my '91 mustang LX, 5.0. i was driving up the mountain at a good pace and came upon this SVT 4 cyl. as i was passing him, he got on it and we were side by side and going faster and faster (never exceeding 65 mph lol) the entire time up the winding mountain. i would have thought the torque from my 5.0 would have pulled away but i didnt. i dont know if his was SVT was stock, mine was with the minor exception of a K&N filter. when we got to the top, he was ahead by a car length, he held up FOUR fingers, i thought he was flipping me off, then i realized he was saying 4 cylinders. also, he was a young punk probably redlining it, i was 35 years old and cautious and didnt push to hard, at least that's what i tell myself to this day.........

 

bhuff30

Founding Member

Dec 11, 2001

6,037

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129

Olathe KS

Jan 22, 2012

#6

• Jan 22, 2012

• #6

haha, great story. Bone stock, the 5.0 and SVO were pretty close to each other in terms of a drag race. The SVO was really setup for the twisties and road courses though. They had Koni shocks/struts, 16" wheels, and lots of other little suspension tweeks.

 

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kevlar28273

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May 23, 2009

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Charlotte, NC

Jan 22, 2012

#7

• Jan 22, 2012

• #7

thanks huff, anything to boost my ego why i lost is appreciated!! it had to have been the koni's (suspension), lighter weight and i still think he wasn't stock. i was....... seriously, there were yellow speed limit signs on an INTERSTATE around corners were 30-45 mph. we may have been exceeding that a pinch.......... still wished i had that 5.0 over my lousy 4.6 i have now.

 

trinity_gt

10 Year Member

Jan 31, 2003

3,125

81

99

Canada

Jan 23, 2012

#8

• Jan 23, 2012

• #8

kevlar28273 said:

i can depress the brake pedal about 2 inches until the front calipers are unable to be turned by hand. i am positive its not an air bubble. what else is there? any and all ideas will be greatly appreciated!! thanks

Click to expand...

Unless you've got mechanical deformation occurring in, say, the flex lines (e.g. bulging), calipers or caliper brackets when the pedal is depressed then I suspect you've still got air in the system. Jack it up and remove the wheels. Have a buddy cycle the pedal while eyeballing the brakes, looking for lost-motion.

Are you sure the calipers are mounted properly? Are the bleeder screws at the "top"?

Does the system hold pressure? If you depress the pedal until you meet a decent amount of resistance and hold it there does the pedal stay or does it sink slowly to the floor?

 

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kevlar28273

New Member

May 23, 2009

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Charlotte, NC

Jan 23, 2012

#9

• Jan 23, 2012

• #9

Trinity, thanks for the thoughts.
i also put on stainless steel flex lines. and heavy duty thick steel brackets that came with the kit.
I specifically did check if it the pedal would stay because that is an indication of a leak. The pedal stays well in position when it is pressed. The other reason I didn’t think it was air is because – in my experience – when there is air in the line you can pump the pedal and it gets better and you can hold it. then when you let off, wait for 30 seconds or so and then press again it goes back down. Mine does not do this. It is very consistent.
lastly, i am 99.999% sure that the are assembled correctly but i am going to take a few pictures and send into SSBC to verify.

 

jetmech807

10 Year Member

Dec 1, 2011

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Crestview, FL

Jan 23, 2012

#10

• Jan 23, 2012

• #10

I put a Wilwood set up on my 03 Last week along with new calipers on the back and a new MC. Sounds just like mine till I bled the MC again. If you don't have bleeders on the MC, crack the lines just like a bleeder screw. Once I bled the MC, I had a rock hard pedal. I bench bled it twice, not sure what good it did, but no pedal till it was bled on the car.

 

trinity_gt

10 Year Member

Jan 31, 2003

3,125

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99

Canada

Jan 23, 2012

#11

• Jan 23, 2012

• #11

Interesting. I've not heard that pumping the brakes could stiffen a pedal with air in the lines. Air is compressible: It shouldn't matter how many times you pump it, the air will continue to compress each time. What you describe (getting a stiffer pedal after one or two pumps) sounds more like internal seals on the master cylinder.

Re the SSBC brakes. I'd wondered if perhaps there was extra cylinder volume in the SSBC calipers that requires more fluid movement to effect the same braking force. If the master cylinder is stock and these calipers have larger volumes than the OE calipers then you'd need extra pedal movement to get the same force. However, I've never read anywhere that a larger master cylinder was a requirement for using the SSBC setup so that's not it.

Perhaps though, you should check the pushrod between the pedal linkage and the master cylinder piston. Maybe you've got too much freeplay and are losing motion there.

 

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kevlar28273

New Member

May 23, 2009

8

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1

Charlotte, NC

Jan 23, 2012

#12

• Jan 23, 2012

• #12

thanks jet, i am going to re-bleed the master cylinder this weekend. then of course re-bleed the system.

 

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kevlar28273

New Member

May 23, 2009

8

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1

Charlotte, NC

Jan 23, 2012

#13

• Jan 23, 2012

• #13

Trinity,
according to SSBC, no master cylinder change is needed but after i had a soft pedal, i figured why not so i replaced with a cobra cylinder. i will check the pushrod also. if the pushrod is touching the pedal, then its adjusted correctly or is there something i can do there to tighten up the throw? thanks!!

 

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kevlar28273

New Member

May 23, 2009

8

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1

Charlotte, NC

Feb 7, 2012

#14

• Feb 7, 2012

• #14

ok jet, you win. unbelievable. It was air in the MC. If you read above I got a phoenix reverse bleed tool. Good tool but still didnt do the job. I finally read the instructions on this tool and watched a DVD. They stressed that the master cylinder has to be level. I have a 5 ton jack that will lift the rear of the car quite high. Put a level on the MC, still not level. I then put a 4x4 under the jack, still the MC wasnt level but just barely the rear needed to be higher. I didnt dare repeat this, so I let all the air out of the front tires. Finally the MC was level. I used the reverse bleeding tool, followed by a normal bleed, and WOW, I have a rock solid brake. So thanks all for the input!! greatly appreciated. But, on a note, what I did, wasnt the smartest or safest thing to do. My rear end was about 3+ feet jacked up, the front bumper was almost touching the floor. Not so safe. Why this MC is at such a steep angle when mounted is beyond me. But this is what I had to do and it worked. I just would not recommend doing this. Again thanks all. been driving my stang with the SSBC brakes and enjoying it again!!