Topic: Brake question - Mustang - (don't shot me, please)
in Forum: General Non-Vette Discussion
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OK, I know it's a Ford, but don't shoot me. I have enough mechanical ability to be dangerous and my friend has less abilities than I.
Helping the neighbor bring his 65 Mustang back to life.
Converted to front disc brakes, new master cylinder, (front section plugged off), new rear wheel cylinders, new shoes, new rear brake line from the preportioning valve to the rear. Bench bled the master cylider. So my two questions are:
1. We have bled the brakes maybe 20 times, still the first pump of the pedal is weak, strong on the second pump, and full pedal on the third pump. What am I doing wrong?
2. We decided to test the system by driving the car in the neighborhood. The left front wheel was locked. Removed the wheel, (needs a new wheel due to backspacing), but the caliper was locked. After maybe 20 minutes you could spin the wheel using two hands, but it was still tight. Do we have a bad caliper, a bad hose, or what?
Confident we have fixed any leaks in the system.
Like I said; don't shoot me, but you gous were a tremendous help when I had Corvette brake issues.
current
1977 Coupe
gone but not forgotten
1996 Grand Sport
1996 Grand Sport
1984 coupe
1974 coupe
1964 roadster
1974 coupe
1964 roadster
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Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
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#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Why is the "front section" blocked off, if you have a proportioning valve?
Joel Adams
C3VR Lifetime Member #56 
My Link 
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
The old master cylinder had only one brake line going to the preportioning valve.
current
1977 Coupe
gone but not forgotten
1996 Grand Sport
1996 Grand Sport
1984 coupe
1974 coupe
1964 roadster
1974 coupe
1964 roadster
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
The problem with having front disc , and rear drums, is the volume of fluid difference between the two types. Disc brake calipers take more volume than a drum brake wheel cylinder. That's why a master cylinder for a typical disc/drum system will have two different size chambers, with the small chamber for the rear(drum), and the larger chamber for the front(disc)
What is most likely happening is the first pump of the pedal is just filling the front calipers, getting ready to apply the brakes. It's taking almost a full press of the pedal to do that, and at the same time, trying to apply the wheel cylinders for the rear.
Does the master cyl you have have two same size chambers, or one large/one small? Usually, the smaller chamber will work the rear(drum) brakes, and the larger one working the front(disc) brakes. The P-valve keeps most of the pressure going to the front. Changing to front discs mean you'll also need to change the p-valve, since the calibrations are different between the two set-ups.
IMHO, you(your neighbor) need a dual line, disc/drum master cylinder, and the correct disc/drum proportioning valve. It's not likely you'll ever get a good pedal with the set-up as it is...
In a previous life, I was a Mustang collector...I had 7 early Musturds when I moved to D/FW in '86, including a K engined '64 1/2. I've grown out of that phase, tho...
What is most likely happening is the first pump of the pedal is just filling the front calipers, getting ready to apply the brakes. It's taking almost a full press of the pedal to do that, and at the same time, trying to apply the wheel cylinders for the rear.
Does the master cyl you have have two same size chambers, or one large/one small? Usually, the smaller chamber will work the rear(drum) brakes, and the larger one working the front(disc) brakes. The P-valve keeps most of the pressure going to the front. Changing to front discs mean you'll also need to change the p-valve, since the calibrations are different between the two set-ups.
IMHO, you(your neighbor) need a dual line, disc/drum master cylinder, and the correct disc/drum proportioning valve. It's not likely you'll ever get a good pedal with the set-up as it is...
In a previous life, I was a Mustang collector...I had 7 early Musturds when I moved to D/FW in '86, including a K engined '64 1/2. I've grown out of that phase, tho...
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Great information; I'll pass it along. My assumption is he will "pony" up for the parts needed.
current
1977 Coupe
gone but not forgotten
1996 Grand Sport
1996 Grand Sport
1984 coupe
1974 coupe
1964 roadster
1974 coupe
1964 roadster
oops, I large and one small chamber on the new master cylinder
current
1977 Coupe
gone but not forgotten
1996 Grand Sport
1996 Grand Sport
1984 coupe
1974 coupe
1964 roadster
1974 coupe
1964 roadster
in Forum: General Non-Vette Discussion
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