proportion valve with disc brk kit

cvicky

cvicky

Senior Member
I got the 55 Fairlane with frt disc brake kit and dual master cyl with proportion valve with dial
I have rear brakes adj to the max
if I have to stop in a hurry the brake peddle gets hard but won't go to the floor
at hwy speed I coast for about 100-200 ft with both my feet pushing on brk peddle


22 inch of vacuum
7' calipers
master 1 1\2 bore
booster seems OK
confused- when I RE/RE rotor to grease bearings pedal goes to floor and I can't pump it up,(bleeding doesn't work either) I have to drive the car and back up several times then pedal comes up
called M P brakes and they are going to take my issue to mornings meeting
 

Attachments

  • IMG_3818.jpg
    IMG_3818.jpg
    32.3 KB · Views: 21
  • IMG_3822.jpg
    IMG_3822.jpg
    46.7 KB · Views: 20
  • IMG_3824.jpg
    IMG_3824.jpg
    46 KB · Views: 19
Last edited:
you should do some more research I have a feeling you did not install properly.if installed properly there should be no reason for the PV.I doubt the van has a PV from factory.is it equipped with booster? if so may be a problem with it or vacuum source.
 
Last edited:
Your master cylinder may be too large. Try one with a 7/8 bore. Or, get all the parts written down and call Master Power brake. Those guys do magic over the phone.
 
I use a simple proportioning block I got at Summit for around $70. All my brake lines and master lines are plumbed to it. Factory-style ones tend to get people in trouble especially the later model ones we used to call a "monkey-valve".

My master is a Ford style 1" bore, manual, no power with GM type discs up front, 11" drums out back.
 
I spoke with Master Power Brakes and to him 22" vacuum 7" calipers 1 1/2" master wich he thinks is corvette
MPB thinks that's all good
he is stumped when I tell him that I can't bring up pedal by bleeding , I have to drive the car and back up several times heavy on the brake to bring up pedal
ps jamming the brakes in reverse is the only way I can lock frt disc
 
I went and looked, just to check my memory. All the Corvette masters I found (restoration, not hot rods) ran from 15/16" bore to 1 1/8" bore. 1 1/2 is a big increase. You'll move plenty of fluid, but you'll need a big leg. The 1 1/8" were shown for power brakes only.

Many aftermarket cylinders come with a spacer, looks like a button, to go in the bore for power brake use. The booster has a shorter rod (since it can't fall out) and without that in place, you bottom the brake pedal mechanically before the boost rod puts full stoke to the master cylinder. I know, I've made that mistake, you chase your tail forever.

Did you bench bleed the master before you installed it, of after you ran it low bleeding them? That's another way to get problems.

The final solution to brake problems is to put pressure gauges on them, and check the pressure at the calipers or wheel cylinders. I've had a couple occasions with conversions where it turned out to be incompatible linings (disc brake pads usually) that just didn't work with each other. Change pads, solved problem. But those are different symptoms from yours.
 
MPB seems to think reducing the bore would be a good start
2 thing are confusing to me
- pushing back piston in caliper is really hard -barely moves
-can't bleed brks from the wheels, can't build up pressure pedal keeps going to the floor
need to drive car in reverse to build up pedal
 
cvicky said:
I got the 55 Fairlane with frt disc brake kit and dual master cyl with proportion valve with dial
I have rear brakes adj to the max
if I have to stop in a hurry the brake peddle gets hard but won't go to the floor
at hwy speed I coast for about 100-200 ft with both my feet pushing on brk peddle
. . .
2 thing are confusing to me
- pushing back piston in caliper is really hard -barely moves
-can't bleed brks from the wheels, can't build up pressure pedal keeps going to the floor
need to drive car in reverse to build up pedal
Click to expand...
I'm guessing there may be two push rods from the brake pedal. One from the pedal to the booster and another from the booster to the master cylinder. If the length & clearance on either aren't correct it will cause problems.

IF the rubber flex hoses are in good shape (not collapsed internally) it may almost be time to take all the aftermarket parts off, then inspect and/or exchange them for different parts.
 
Most brake problems I see on the forums start with those crappy Corvette "style" masters. I would ditch it and get a '72 or so Mustang 1" master for a disc/drum application, but it does have to fit your booster.
 
if you cant bleed from caliper and pistons wont return ck hoses and maybe you have a bad pv valve or master are your rear brakes working with no problems? maybe bypass pv and see if its better could the master be setup for disk/drum or disk/ disk was it a kit or pieced together. i had disc/disc with a booster on my wagon no pv disc/drum on my ranchero same no pv and no problems
 
You must log in or register to reply here.
Back
Top