**Vehicle... 1928 A tudor with flathead running gear. **Scenario... 39 Ford front brakes, new cyls, new linings, hoses. 47 pickup rear brakes. New 1/4" brake lines with residual valves, one front, one rear, both situated near the master cyl. New 65-66 Mustang dual master (drum/drum) situated below level of the wheel cyls, ie: under floor. **Problem.... Have bled the f****g things about 57 gazillion times and best I can get is pedal hardens up after 3 or 4 pumps, but then loses it when pedal is released. **Incidentals.... If I pump it up and hold it down, the pedal stays pumped until I let go. Also, when pumping pedal with reservoir cap off, fluid spurts out of the rear reservoir. I know this aint normal! Drums have been adjusted to locking, then backed off till they spin. Handbrake is working. **Possibilities... I have the master mounted back to front from original firewall mounting, with the rear lines mounted to the (now) rear port and the front lines mounted to the (now) front port. Maybe they need swapping around? Maybe the master is faulty? The other possibility is that I will go f****g mad and drive the whole thing into the ocean.....
Is the bore size of the master cylinder less than an original early Ford one? If so that will be the biggest part of the problem.
Are you sure on the master cylinder application; if I remember right '65-'66 Mustang still had single master cylinders. Do you know the bore size of the cylinder you have?
Front should be on the rear !! Rear should be on the front. But in reality if you have drums all the way around you should be using a single M/C. Do you have check valves in the system???
I'm sure you bench blead the master right. Sounds like everything else is right, must be a bad master cylinder. It happens.
bingo! make sure you have them adjusted correctly first. slight drag. Very critical on 4w drum brakes. We've become spoiled with the new fangled disk brakes
I was taught to adjust them until you could only get about a half a turn when spun. If they spin freely they are not adjusted correctly and the pedal pumping is just taking up pedal play IMHO
Those front brakes are the old original type hydraulics, I think they're properly named "Lockheed" brakes. Not sure about the'47 p'up rear brakes, whether Lockheed or Bendix. But a proper adjustment on the early brakes includes, on initial installation and after relining shoes, an adjustment of the shoe anchors before you adjust the shoe distance from the drum surface. Been a long time since I worked on the old style, but this could be the problem. A search here will find ithe procedure, I'm sure because I remember reading it not long ago on a post.
are the shoes "arced" to fit the curvature of the drum? I've had this problem before -- take the drums off and set the shoes in and see if they "rock" they shouldn't if they DO, that is the "play" compensated for by steppin several times on the pedal to force the shoes to match the drum circle -- find someone w an old school brake machine that has the capability to arc grind shoes to match the drums -- I never did drum brakes w-out havin the shoes arced as well to fit the drums - -even *then* there was a "wearin in " period I'd warn the customer to be carefull of, and I'd adjust em free after 500 miles
your problem is you got a "new" master cylinder. probably a speedway special... had one junker in a model A sedan once....
Maybe you aren't getting a full squirt because your master plunger isn't returning completely? Do you have an 1/8" of play before the pedal rod hits the plunger?
First questions Did you adjust the brakes correctly before bleeding cylinders? 2. What size master cylinder did you purchase, has to be around 1 1/16" bore. If you cannot get a solid pedal after 2 pushes the pedal is not displacing enough fluid or the shoes are too far away from drum surface. Your pedal should travel about 1 to 1-1/2" before starting to stop and be solid after that.
I looked though Ford drum/drum master cylinders and even the 70 F250 has a 1 inch bore master cylinder. Then I checked 69 F350 and it has a 1.125 bore master cylinder for the drum/drum brake setups. That might be something to check into as far as bore size goes. I'm still thinking that you need to get the brake adjustment right on the money first though.
There's no reason not to look for a disc/drum or disc/disc master as well, although the 1 1/16" bore size will still be rare. I would think using an 1 1/8" bore master would increase pedal efforts too much with manual Lockheed brakes, but there have been several that use a 1" with no problems. You will loose a little pedal, (longer stroke with the benefit of slightly lower pedal efforts), but as long as a full stroke can be achieved, (in most cases it will) the 1" should work OK.
The main thing is the master MUST be bench bled and air free before installing. Also, all drum brake cars I have ever seen use 3/16 brake lines. You said you have in-line residual valves, does the drum brake master cyl not already have them built into it ? I know mid 60s GM master cyls did. Maybe that is also a problem . Good luck and dont give up, it always works out to be something simple.
One test i try is to clamp each flexi line starting with the back one and see if the peddle changes. If and when it gets better that's the section to focus on and if no change its the master cylinder. Good luck. JW
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