Author Topic: Brake drag/slow pedal return  (Read 1071 times)

Offline 68NordicCat

  • Jr. Member
  • **
  • Posts: 60
Brake drag/slow pedal return
« on: March 29, 2017, 12:54:44 AM »
12/67 SJ built 68 Cougar - power front disc rear drum brakes. Rebuilt booster, reconditioned original distribution block, repro proportioning valve (which I hear now might not be much count). Have bled the system, but brake pedal still feels squishy from time to time. Bigger problem is very slow pedal return. From what I've read the most likely culprit is the booster, but I've also heard it could be the proportioning valve. I now have a rebuilt original block and valve assembly which I could change out (easier than the booster). Question - is there a way to diagnose the specific problem without just continuing to purchase and swap out parts (or resorting to a bungee cord :P)? Thanks.

Dan
12/67 SJ Built 68 J code 4-spd Cougar

Offline Murf

  • Sr. Member
  • ****
  • Posts: 364
Re: Brake drag/slow pedal return
« Reply #1 on: March 29, 2017, 11:32:54 AM »
Typically the booster is the cause of a slow return.  Many times it is caused by the rear seal of the master cylinder leaking brake fluid into the booster and swelling a certain part.  In some cases the brakes will not release until you hook your toe under the pedal and force it to return to the "off" position. 
John Murphy

1965 "K" GT fastback Honey Gold exterior, Ivy Green and White Pony interior, many options
1966 Conv., high option, removeable hardtop, thermactor "C" engine, AC, Springtime Yellow exterior, Black Pony interior
1968 California Special, "J" code, ,many options, white with red interior

Offline preaction

  • Hero Member
  • *****
  • Posts: 715
Re: Brake drag/slow pedal return
« Reply #2 on: March 29, 2017, 05:04:34 PM »
Dan, don't hesitate to give WCCC a call they work on issues like this every day and are happy to help.
8R02S125064- January 6 1968  SJ   7F93S591808 - April 28 1967  Dearborn   7F91S544039 - December 17 1966 Dearborn

Offline rockhouse66

  • Hero Member
  • *****
  • Posts: 658
Re: Brake drag/slow pedal return
« Reply #3 on: March 30, 2017, 10:52:07 AM »
How old are the brake hoses?  These have been known to look great on the outside but swollen on the inside, acting like a one-way valve.  This will cause drag and slow release or even complete lock up in some cases.
Jim
'66 GT FB, '69 CJ Grande

Offline 68NordicCat

  • Jr. Member
  • **
  • Posts: 60
Re: Brake drag/slow pedal return
« Reply #4 on: May 20, 2017, 04:52:00 PM »
Hoses are all new. Replaced the booster which seemed to correct the pedal return issue.

Now searching posts to troubleshoot a new problem - can't lock it up. I have brakes but not enough for an emergency stop. Seems like I get a good start when applying firm pressure but then feels like it releases and won't increase braking much even standing on the pedal. It's front disc rear drum, have fully bled the system, rebuilt calipers, new rotors, new drums, new pads, new cylinders, new lines, new hoses, new booster, new master, rebuilt block, repop proportioning valve. Scratching my head.

Any ideas appreciated.

Dan

12/67 SJ Built 68 J code 4-spd Cougar

Offline preaction

  • Hero Member
  • *****
  • Posts: 715
Re: Brake drag/slow pedal return
« Reply #5 on: May 21, 2017, 07:19:51 PM »
Dan, I went through this same issue with my 67 cougar and it turns out at least on the east coast that the brake pads available at NAPA for me is a generic organic compound pad. I just this month looked at this again  as a problem I wanted to be finished with and found the only step up in brake pads was a semi metallic from Hawk for $150 and with a proper bedding my brakes will now lock up.
8R02S125064- January 6 1968  SJ   7F93S591808 - April 28 1967  Dearborn   7F91S544039 - December 17 1966 Dearborn

Offline 68NordicCat

  • Jr. Member
  • **
  • Posts: 60
Re: Brake drag/slow pedal return
« Reply #6 on: July 16, 2017, 10:37:59 AM »
I may try new pads but it really feels mechanical. I was on a shakedown after trying to resolve a power steering fluid leak and tested the brakes again - at 25-30 mph applied firm, sudden pressure like an emergency stop. The brakes start to engage and then just release with little to no stopping power. Under normal driving conditions, i.e. no aggressive breaking, things seem fine and the car stops easily. Wouldn't know there was a problem until you try to lock it up. I've bled the system several times and am running silicon fluid at the suggestion of a friend (hardcore Cougar guy that says he's never had problems and runs it in both his 68 and 69). Could a proportioning valve problem cause conditions like this? Would really like to drive the car but can't justify it until this problem is solved.
12/67 SJ Built 68 J code 4-spd Cougar

Offline preaction

  • Hero Member
  • *****
  • Posts: 715
Re: Brake drag/slow pedal return
« Reply #7 on: July 16, 2017, 06:48:00 PM »
I too am using silicone fluid and my system has been good for 15 years. I did talk to booster Dewey about this problem and his point was to look at the booster if your running silicone fluid, if it leaks into the booster it will cause swelling.
8R02S125064- January 6 1968  SJ   7F93S591808 - April 28 1967  Dearborn   7F91S544039 - December 17 1966 Dearborn

Offline 69SCJQ4.30

  • Jr. Member
  • **
  • Posts: 81
Re: Brake drag/slow pedal return
« Reply #8 on: August 31, 2017, 04:51:59 PM »
Not sure if you ever resolved your issue but that sounds like the problem my dad has had with organic pads and that is all most auto stores sell now. Like preaction said try to find some kind of semi metallic pads, but hawk I think may be some of the last you can find.