Converted a tri five to power front discs/stock drum rears. Everything's new, double dia. booster, GM type combination valve. Have bled this sucker about 2 quarts worth, no brake pedal. - vette type master cyl. bench bled, plugged, hard holding & no bleed down -plugged front outlet on master, have hard pedal for rears, seems o.k. there. Took out plug, hooked up fronts, bled, no pedal -pinched front lines, got rear pedal again -removed pinch from one caliper, no pedal. Pinched it back, tried the other and same thing, no pedal. Everything is new, wonder if both front calipers are crap, or if the combo valve is screwed up (tried the button push, it didn't move) Sure would appreciate some opinions. One of my three hairs just fell out. cooger
yeah, bleeders on top, the do gravity bleed fine, plus pedal bleed o.k. I believe they can only go on one way, the install seems o.k.
i have seen even the most experienced mechanics get the calipeers crossed side to side and put the bleeders on the bottom. it happens. other than that, are the calipeers new or used?
new, got 'em from a parts store. What I can't figure out is why there no hydraulic pressure. The things are full of fluid, it runs out and pumps out when I bleed it, but won't build any pressure when the line is unpinched.
ck your push rod adjustment also there is a booster to master cylinder push rod adjustment on the booster good luck Andy
The line going to pass. side has about a 1/2 circle in it from the combo valve outlet & then goes down. The other side goes straight down from the combo to the caliper inlet. Even this one causes the pedal to go down when the other one is pinched off.
I have about 1/8 to 1/4" free play before the rod hits the booster plug. I'm wondering if there's a port in the combo valve that's not covered, uncovered, etc. because of the rod. Tks for the input.
right, its a homebuilt but with all new stuff, double dia. booster, gm combo valve, etc. I used the stock hole in the pedal/clevis (this car, a 55, was a no power brake, one hole) for the pushrod, it threads onto the booster with a coupler. Pedal stop?? The only one I have is for the return, pedal will go to floor. ????????
Don't you have to build pressure to bleed brakes? Also, have you tried different adjustments on the proportioning valve to see what effect that may have, if any? Just playing the odds.............it would seem that the master cylinder might be bad under pressure rather than both wheel calipers.
Cooger, the power brake uses a different pedal "ratio" than manual.. Manual is 4 to 1 and power is 6 to 1.. The hole in the pedal for manual brakes is CLOSER to the pivot point and farther away for POWER brakes.. You need to drill a second hole further down the pedal . The kits come with angled brackets for the booster/master to move the pushrod down the correct amount. I can check the cars @ the shop and measure how far down you need to drill the hole... I found this out the hard way the first time I made my own brackets, etc. Same problems you are having.. Good luck Dave Hey, I just went out to my garage and looked @ my 55.. I did a manual disc conversion on it over 10 years ago (haven't driven it more than a mile since, LOL ! ) My feeble memory is working again... The flat part of the pedal is about 1 " long under the MANUAL pushrod hole. (then it curves around the steering coloum.) Drill the new hole as close to the curved part as you can, while still staying on the flat... The booster that you need ( angle brackets) will come from a 68 to 72 chevelle, or 69 camaro, or 68 to 74 nova (and all olds,pont, etc versions). If your booster has studs on the firewall side, stainless steel brakes (and others ) sell just the angle brackets separately. The easy way to determine the exact location for the new hole is to install the angle brackets and bolt everything to the firewall. The pushrod will be in the correct spot. I can measure the 57 Nomad tomorrow if you need the exact measurment... Dave
Dave: You are backeards on the ratio numbers,but correct one the hole posision. Cooger : You may have a bad M/C with the disk side bypassing under pressure. Old partsman quote "Just because it's new don't mean it's worth a F^^K"
Sounds like the check valve on the master cylinder piston is not working. Being new, I would think it is defective, but all it takes is one small piece of trash to keep it from seating. good luck,
Tks guys for all the inputs. I went out last night, hooked up a pressure gage to the front disc side, even though I had a real kluge setup for the gage with air all in the line, I did see about 40 psi, but had to be pumping to see it. Went to the combo valve output for the fronts, same thing. Tried the rear for the drums , it showed about 90 psi on the pump. I rebled the master in the car with the booster, hooked up a couple of lines feeding back into it, and damm, I had a rock solid pedal after plugging both the front and rear-again. I'm thinking like some of you that there's something fishy about front disc side of the master, I seem to remember that it actually lost some pressure while I was pumping it. BUT, AND THANKS TO DAVE, I DID MAKE MY OWN BRACKETS FOR THE BOOSTER, DIDN'T USE THE ANGLED CHROME ONES, THEY REALLY STUCK THE BOOSTER OUT FRONT AND I DIDN'T WANT THAT SO I CHANGED THEM AND THEN HOOKED THE ROD UP TO THE STOCK HOLE IN THE PEDAL---THAT SURE SOUNDS LIKE WHAT DAVE SAID ABOVE. My car is a manual trans as it came and I 'm using a Muncie so I didn't change the clutch/brake pedals. Will the hole be in about the same location as Dave said????
Do you have the correct brake line location on the Master going to the correct set of brakes...front on the Master to the rears, and rear on the Master to the fronts? From the different pressures you're getting, they sound reversed...
A thought ! You don't have those odd ball low drag calipers do you? If so get the regular one as those take a special M/C because of the added volume needed to work them .
Dang John, never thought of that! El Supid question-how do you know? These are supposed to be off a, like, middle nineties Chevy pickup-supposed to be standard on just about all of the 1/2 tons until now I suppose. They fit the mount fine, etc. tks cooger
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