1968 Mustang Brake problems - Ford Mustang Forum
Reply
 
LinkBack Thread Tools
post #1 of 24 (permalink) Old 04-19-2008 Thread Starter
Rookie
 
daysvilleman's Avatar
 
Joined: Apr 2008
Location: Pulaski
Posts: 10
 
1968 Mustang Brake problems

I have a 1968 Mustang with the drivetrain and braking system out of a 1970 cougar. The car has rear drum front disk power brakes. Ive already put a new Master cylinder, for the cougar setup, on the car. It was originally a 200 I6. My problem is the brake pedal had no resistance until you press it in 3 or 4 inches,at which point it rock hard. Within that 3 to 4 inches is your braking, which if way too touchy. I believe the front brakes are applying too much. It still has the original distribution block which is probably not a good idea. Would there be a way to correct this with an adjust proportioning valve if that were the case.

thanks
daysvilleman is offline  
Sponsored Links
Advertisement
 
post #2 of 24 (permalink) Old 04-19-2008
GLOBAL MODERATOR
Mustang II Member
Classic Member
V6 Member
4.6L Member
5.0L Member
 
heavy metal's Avatar
 
Joined: Oct 2007
Location: Bradyville
Posts: 30,173
                 
Garage
Send a message via Yahoo to heavy metal
welcome to the site,enjoy!!!! are the rear brakes adjusted right?are you getting good pressure to the rear brakes?


Cherish those around you,for at the blink
of an eye,they can be gone.

AFM GLOBAL MODERATOR
heavy metal is offline  
post #3 of 24 (permalink) Old 04-19-2008 Thread Starter
Rookie
 
daysvilleman's Avatar
 
Joined: Apr 2008
Location: Pulaski
Posts: 10
 
yeah I pulled the drums. The shoes are adjusted out. Cant turn them with car in air and brake applied.
daysvilleman is offline  
post #4 of 24 (permalink) Old 04-19-2008
GLOBAL MODERATOR
Mustang II Member
Classic Member
V6 Member
4.6L Member
5.0L Member
 
heavy metal's Avatar
 
Joined: Oct 2007
Location: Bradyville
Posts: 30,173
                 
Garage
Send a message via Yahoo to heavy metal
sounds like all is working right,you may need to change the valve if you want more pressure at the rear brakes.most disc and drum systems are 70% front and 30% rear stopping power.


Cherish those around you,for at the blink
of an eye,they can be gone.

AFM GLOBAL MODERATOR
heavy metal is offline  
post #5 of 24 (permalink) Old 04-19-2008
SHELBY GT 350 Member
Classic Member
 
Veronica's Avatar
 
Joined: Dec 2003
Location: Houston
Posts: 9,078
     
Hello. It sounds like you might actually have a couple of problems. The brakes that you have in the car now should have a proportioning valve for the rear brakes and a check valve for the front discs. The rear brakes aren't hitting soon enough and the fronts are hitting too hard. If the check valve is bad, that would account for the front, and the proportioning valve would account for the rear. Unfortunately, neither are adjustable on the original system. I'm pretty sure that the 69 Cougars used the same master cylinder push rod as the 69/70 Mustangs, so that isn't going to be part of the problem. Replacing the check valve and proportioning valve with adjustable units should straighten you right out. Hope that helps.
Veronica is offline  
post #6 of 24 (permalink) Old 04-19-2008 Thread Starter
Rookie
 
daysvilleman's Avatar
 
Joined: Apr 2008
Location: Pulaski
Posts: 10
 
Are you referring to the distribution block?
daysvilleman is offline  
post #7 of 24 (permalink) Old 04-19-2008
SHELBY GT 350 Member
Classic Member
 
Veronica's Avatar
 
Joined: Dec 2003
Location: Houston
Posts: 9,078
     
Quote:
Originally Posted by daysvilleman View Post
Are you referring to the distribution block?
Hi again. Nope. Based on the way that you've probably never even heard the term ' Check Valve' before, I'm guessing that yours got lost in the shuffle somehow. Your system should have a distribution block, a proportioning valve and a check valve. The purpose of the check valve is to keep the brakes from doing what it sounds like your brakes are doing. The proportioning valve balances out the force that's applied to the front and back. The check valve makes them hit at the same time. If you imagine two people holding a rope and one of the people gives the rope a flip, you will see a wave travel down the rope. If you imagine two pairs of people holding ropes with one rope being twice as long as the other, and they give both ropes a flip at the same time, the wave will hit the other end of the short rope first. That's what your brakes are doing. The check valve is there on the front brakes to slow down the wave in the short rope enough to make sure that both waves start AND finish at the same time.
Veronica is offline  
post #8 of 24 (permalink) Old 04-19-2008 Thread Starter
Rookie
 
daysvilleman's Avatar
 
Joined: Apr 2008
Location: Pulaski
Posts: 10
 
I did try to use one of those adjustable proportioning valves . I installed it between the master cylinder and the distribution block and it made no difference. As far as i know their are no valves between the distribution block and the the brakes themselves. I will double check that though. The car was original set up with manual 4 wheel drum.

Thank you very much
daysvilleman is offline  
post #9 of 24 (permalink) Old 04-19-2008
SHELBY GT 350 Member
Classic Member
 
Veronica's Avatar
 
Joined: Dec 2003
Location: Houston
Posts: 9,078
     
Hi again. What the Cougar would have had originally would be the same thing as a 69/70 Shelby. That's the set-up that you want in your car. Knowing that might help you out on finding parts, diagrams, etc... I should have the diagrams and part numbers stuck away somewhere. I'll see if I can find that stuff.
Veronica is offline  
Apprentice
Classic Member
 
RemRem123's Avatar
 
Joined: Mar 2008
Location: Charlotte
Posts: 208
 
Do your rear wheels lock up during hard braking?
I just did the Scarebird disc swap for the front and I haven't swapped the m/c for a disc/drum
Its sounds to me like Veronica is right, but you need to make sure your M/C is for disc/drum, one of the resevoirs should be bigger than the other one

1968 Mustang Coupe with 331 stroker, Explorer 8.8" rear-3.73 Posi, '88 T-5,hydraulic clutch, dual Flowmaster exhaust, 4-wheel discs!
RemRem123 is offline  
MACH I Member
Classic Member
5.0L Member
 
The Greek's Avatar
 
Joined: Nov 2006
Location: Jacksonville
Posts: 3,184
 
You won't have any check valve to locate because you have the dual braking system. It's in the M/C. You must have the correct M/C for the disc/drum system, though. You also have the adjustable proportioning valve installed wrong. The P/V is plumbed into the rear brake system after the distribution block. It should not be connected into the front system at all. If you have the original P/V it will be located just before the flex hose for the rear brakes. Don't have but one of these in the system, the original or the adjustable type, but not both. If the brake lines that are on the car was for an all drum system there won't be a proportioning valve in the system.

As for the pedal travel, you may need to adjust the pushrod that is between the master cyl. and the brake booster and make sure that the vacuum line's check valve at the booster's vac. inlet is working.
The Greek is offline  
Rookie
Classic Member
V6 Member
 
BIGREDRASA's Avatar
 
Joined: May 2008
Location: Plattsmouth
Posts: 35
 
You say you're using the original distribution block. Did you do anything to it? Check out http://i245.photobucket.com/albums/g...rakeDistV1.jpg

The block should now only split flow to the front brakes. The front port is plugged. The line to the rears goes from the MC to the Proportioning valve.

Tony Salazar, Retired USAF Mustang, 2004 40th Anniversary Mustang Convertible, 3.9L V6. Before KISS, there was Okham's Razor: "The simplest answer is usually the correct answer." Sir William of Ockham
BIGREDRASA is offline  
post #13 of 24 (permalink) Old 05-15-2008 Thread Starter
Rookie
 
daysvilleman's Avatar
 
Joined: Apr 2008
Location: Pulaski
Posts: 10
 
Alright i changed out the Distribution block to the Proper block out of a 1970 w/ power disc. This seemed to eliminate the hard stops, but the pedal still had little resistance. Found that the Brake booster was giving me no boost. Replaced it with a remanufactured one and upon installation found that the Master cylinder Push rod was too long. I tried adjusting it to its shortest length and its still about an inch too long before i can get the M/C properly mounted on the booster. Any suggestions on how to handle this. Im hoping this is my last hurdle to get some good brakes.
THanks
daysvilleman is offline  
MACH I Member
Classic Member
5.0L Member
 
The Greek's Avatar
 
Joined: Nov 2006
Location: Jacksonville
Posts: 3,184
 
Sounds to me that you have the wrong booster or master cyl. There shouldn't be anything that is that far off.
The Greek is offline  
post #15 of 24 (permalink) Old 05-19-2008 Thread Starter
Rookie
 
daysvilleman's Avatar
 
Joined: Apr 2008
Location: Pulaski
Posts: 10
 
Well it was the wrong Booster. Turns out the booster that was originally in the cougar parts car was out of a 1970 Mustang.It still doesnt make any sense because the master cylinder i have is listed to fit both a 1970 Mustang and a 1970 cougar, so i would think that both boosters should bolt up to the same m/c with no issue. Anyways i now have it installed but the brakes are still screwed up. The pedal has such so Little resistance when you push it that the spring will not surpress enough in the brake light switch to turn them on. Its almost like their is too much power booster if that is possible. Im getting pretty good braking. When the brakes apply you dont feel it in the pedal though, You need to float the pedal in that "sweet spot" to gradually stop. I am at wits end here. Anyone that has possibly heard of such a thing it could use advice.

One more note is when you press the brake all the way down and let it off the engine studders for just a second.

thanks
daysvilleman is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Ford Mustang Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a VALID email address for yourself, otherwise you will not receive the necessary confirmation email needed to confirm, validate and activate your new AFM member account.

Failure to provide a VALID email address, will result in the cancellation of your new AFM member account registration.

Email Address:
OR

Log-in









Random Question

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183