I need some suggestions. My cousin has a 63 Galaxie and decided to go with a disc brake set up. He put all new lines, new master/booster corvette system, S-10 calipers and disc, a porpoti**** valve. We've tried everything. (that we can think of.) The problem we have is you hit the brake and it goes down slowly till it hits the floorboard. but if you pump it, and hold the pressure will hold. What causes this, there seem to be no leaks. Thanks for the help in advance.
Are your bleeders facing up or down. If Down, switch sides.... meaning if your right caliper is on the left, bleeder will be down, Air will be trapped with no way out..... They need to be facing up Its actually very easy to do... Also I am not sure what brake switch your runnin, if its mechanical on the pedal, make sure your pedal is coming all the way up, and your getting a full stroke. If not, adjust the switch, or back it off till you get pedal and system bled, the readjust. If its an inline switch never mind..... Residual valves make bleeding easier, especially 1 man bleeding....
Isolate and eliminate ,,, Make sure everything is adjusted properly. The 1963 rear drums need a RPV, & the 1963 master had one for the rears ( 1 for fronts too). Your new master probably doesn't have them built in so you'll need to supply the 1963 rears with one. Disconnect lines & Get plugs for the master. Should be rock hard pedal. This eliminates the master as a problem. No pedal & master has issues . There are several possible here. Now plug valve at rear circuit or the rear hose- then bleed fronts and your rear plug. Good pedal eliminates fronts as problem. No pedal = problem Now hook up rear brakes and bleed - no pedal = problem at rears - good pedal = done
may well be a bad master cylinder. the fluid pressure is byp***ing something under light pressure. pump it up and hold hard pressure and the rubber seals expand and seal better.
i would also say it's a bad master, light pressure and the pedal slowly goes down, cl***ic bad master.
Do you have the parking brake hooked up to the rear calipers? If the rear calipers have the arm on the back for the parking brake you will get a spongey soft pedal if there is no tension on the parking brake arm to keep the caliper piston in position.
First of all. Did you look under the bed?... In your running shoes? Seriously though sounds like M/C byp***.
I'm with the m/cyl issue,....and then be sure you have residual check valves for the rears, per post #2. You didn't mention using rear disc, so I'm guessing the rear drums are still in place. Drums need a 10 psi residual check valve. 4TTRUK
That's usually caused by air in the system in my experience. The clue is pumping the pedal compresses the air till the system finally comes up under hydraulic pressure. When you install a new system you have to bleed the system a lot more than you think. I use a liter or so brake fluid getting all the air out. Sometimes I go over the system with a rubber hammer trying to knock loose any trapped air bubbles when I have a problem like yours. Plug the lines one at a time at the distribution points and see which circuit is causing the problem. Also, make sure all the bleeders are pointing straight up and you're not letting air back in when bleeding by cracking the bleeder too far open. I use speed bleeders once I have enough fluid in the system to make them work. Did you bleed the master cylinder first? I do it on the car using home made lines. Also, make sure you're getting the piston to the bottom of the master cylinder when bleeding it. An adjustable push rod is sometimes needed.
If he does...(and I doubt it) he'll be flooded with "TOL' JA SO"... BTW, the cool pic of the dual M'cyl with the looped-over lines? Go ahead, bleed the cyl. like that. Now, after 'eliminating the air', look closely at the fluid in the reservoir. Like 7 Up! All those little 'metalflake looking floaters' are tiny air bubbles. Those'll get that pedal as mushy as Don Ho. ("Tiny..."
I've heard that when you first begin the bleeding process, push the plunger an inmch or so a few times before pushing it all the way. That allows the cups to get wet rather than flopping them inside out.
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