Soft Pedal Bad Performance

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wakeboardan

Founding Member

Mar 6, 2002

611

0

0

San Diego

Oct 19, 2009

#1

• Oct 19, 2009

• #1

I just got finished bleeding my brakes for the 5th time after converting from front drum to front power disc brakes. The pedal is low and soft, and it almost feels like the brakes drag after releasing them. I have the rear proportioning valve screwed counter clockwise (so unscrewed as far as it will go to decrease). I have to push the pedal to the floor to get it to stop and its weak. I have not taken it past my long driveway for this reason. My kit came from chockostang, I used his new pedal, new rod, MC, & booster. I have good vacuum as well. I have reviewed the entire brake line system and cannot find any leaks, my MC stays full as well. Any ideas on a solution to these symptoms? This conversion has been a long project, but i'm dieing to take the mustang on the road with adequate brakes once I can get it goin.

 

jcode68

Active Member

Jul 15, 2003

892

1

29

Massachussetts

Oct 19, 2009

#2

• Oct 19, 2009

• #2

Possible the rod is not adjusted properly. How did you set it?

 

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wakeboardan

Founding Member

Mar 6, 2002

611

0

0

San Diego

Oct 19, 2009

#3

• Oct 19, 2009

• #3

Rod was solid, didn't have any adjustment, I just hooked it up to the brake switch and pedal as it was...

 

2

2+2GT

10 Year Member

Apr 25, 2009

3,333

10

79

Southeastern Pennsylvania

Oct 19, 2009

#4

• Oct 19, 2009

• #4

Have you checked the pushrod headspace? What booster is it?

 

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ks65stang

Member

Nov 4, 2002

184

0

17

Kansas City Metro, Lenexa

Oct 19, 2009

#5

• Oct 19, 2009

• #5

I have the same problem after installing the Scarebird front disc swap. Pedal to the floor w/ little braking but I have nothing hooked to the rear as I'm in process of doing a 9" rear axle swap. I have not had the car on the road for a while and wont for at least 6 months. I have just been rolling around the drive way and garage. I thought this was probably my issue as nothing is hooked to the rear, but after reading your thread maybe not, so I will follow this thread, sorry I have no answers.

 

tx65coupe

Active Member

Nov 29, 1999

1,551

1

37

Oct 19, 2009

#6

• Oct 19, 2009

• #6

You may need an adjustable push rod like this.

Mustangs Unlimited - The Premier Source for Mustang, Shelby and Cougar Parts and Accessories

Is the pedal lower than it was before when its up?

 

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wakeboardan

Founding Member

Mar 6, 2002

611

0

0

San Diego

Oct 19, 2009

#7

• Oct 19, 2009

• #7

I would say that the pedal is lower than usual. Not a huge amount though. If I get an adjustable push rod, would the idea be my existing is too short and I need it longer? Dan Chocko said its a new original booster, I didn't see a particular brand name on it.

 

6Stang7

New Member

Jun 1, 2003

1,470

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0

Livermore, CA

Oct 20, 2009

#8

• Oct 20, 2009

• #8

You adjusted the bias valve so that the rear brakes are getting no pressure?

 

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wakeboardan

Founding Member

Mar 6, 2002

611

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0

San Diego

Oct 20, 2009

#9

• Oct 20, 2009

• #9

correct, wrong idea?

 

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ks65stang

Member

Nov 4, 2002

184

0

17

Kansas City Metro, Lenexa

Oct 20, 2009

#10

• Oct 20, 2009

• #10

6Stang7 said:

You adjusted the bias valve so that the rear brakes are getting no pressure?

Click to expand...

Yea, thats what I did considering they are not hooked up, I also didn’t fill the rear brake reservoir in the master.

Wakeboarden, please post the solution when you figure it out as I have my coupe up on jack stands fixing some rust issues and it will be a while till I address the brakes, thanks.

 

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wakeboardan

Founding Member

Mar 6, 2002

611

0

0

San Diego

Oct 21, 2009

#11

• Oct 21, 2009

• #11

I have now replaced the entire rear drum system, and it is very obvious that the fronts are not engaging as much as the rears are. I have bleed the system now 8 times and have absolutely no air in the lines. If I increase pressure via the prop valve those rears just engage much faster. I have decreased my prop valve completely, but somehow need to find a way to get my fronts to engage harder and sooner. With the front end of the car on jacks, my buddy pressed the pedal to the floor, and I was able to barely turn the actual tires(both passenger and drivers side) by hand. An adjustable rod was suggested previously which I have ordered, but how exactly would a longer rod fix the front engagement? Seems to me it would just make the rears act that much sooner along with it.

 

degins

Member

Sep 18, 2004

361

0

17

Texas

Oct 21, 2009

#12

• Oct 21, 2009

• #12

wakeboardan said:

I have now replaced the entire rear drum system, and it is very obvious that the fronts are not engaging as much as the rears are. I have bleed the system now 8 times and have absolutely no air in the lines. If I increase pressure via the prop valve those rears just engage much faster. I have decreased my prop valve completely, but somehow need to find a way to get my fronts to engage harder and sooner. With the front end of the car on jacks, my buddy pressed the pedal to the floor, and I was able to barely turn the actual tires(both passenger and drivers side) by hand. An adjustable rod was suggested previously which I have ordered, but how exactly would a longer rod fix the front engagement? Seems to me it would just make the rears act that much sooner along with it.

Click to expand...

As suggested above, check the clearance between the pushrod, at the front of the booster, and the end of the master cylinder piston. It should be about 0.030" inches. If there is too much clearance, the pedal will have excessive travel. Have you talked to Dan at chockostang? I'd bet he'd give the same advise.