I don’t come on here much at all anymore asking questions but this one is killing me. Brake pedal is spongy and goes to floor. System. -Boling bros Lincoln style brakes. -3/16” brake lines -‘67 mustang dual pot drum/drum 1” bore MC -willwood 10# residual valves. -tee for brake lights. -shoes aligned and adjusted for slight drag. Yes I’ve done a search and have tried everything I read on here and ford barn. Ive pretty much done every method of bleeding under the sun. Latest method I’ve done is as followed. - Re-bench bled master cyl. Good no bubbles. - Cap rear port. Bleed fronts first. For stiff pedal. Hand vacuum first then pump pedal and hold bled. Good. - Connect rear brake line to MC. Vacuum bleed first then pump pedal and bleed. Good. While bleeding I notice a stream of small bubbles coming out of all 4 bleeder. Thinking it’s the bleeder letting air by threads but have a bit of teflon tape on them to try and reduce that. After all bleeding is done push pedal. Feels firm. Promising. Goes about half way down and gets firm. Move car back and forth pedal basically goes to floor but stops car. Jam on brake pedal stops car but not fast enough. Park car pedal gets firm as before moving car. Suggestions? 1.25” bore mc? Should I just can the dual pot for a single ? Help ! Pictures are attached to just show if lines off master are what is causing air in system still. Rear backing plates are nothing new of what others have done when using model a rear end.
I can't give any testimony, but the bleeders I was raised with, were pressure bleeders. Many then had under floor masters. Using suction ( vacuum ) leaves me to wonder.
You may have a fluid leak somewhere. Go out with a flashlight once it gets dark and look at everything. Wet spots are easy to spot using this method.
I had some trouble a few months back on an entire new brakes system, new wheelcylinders, lines ,hoses ,shoes, mastercylinder., fought with it a couple weeks, sometimes id get a "decent" pedal,, . sometimes would go to floor, not anything i felt comfortable driving with by any means. in my case it was a faulty brand new mastercylinder. results may vary.
I would try another master as well. I have pretty much the same system, using a’68 Mustang drum/drum master, and it works fine. I do have 1/4” lines but that should make no difference.
This is the second master I am on. Thinking my first one was junk hahaha. Wondering if reverse bleeding will get fluid in lines and all air out. Push fluid through bleeder to master. I am 100% positive the master is good. There is just air somewhere. Narrowing it down to front part of car it seems. Capped front port on master. Rear line connected. Firm/hard pedal and stops half way of throw.
Are you properly bench bleeding the master cylinder before putting on the car? I went thru this just once, it was on a jeep. Bench bleed master cylinder and installed. Had the exact same problem your having. Finally I pulled the lid off of the MC and had a buddy SLOWLY go down on the pedal to see if any movement of fluid. That's when I noticed tiny air bubbles coming out of the reservoir of the MC. if I went all the way down and back up it did nothing, if I went slowly then air bubbles would surface, when the bubbles stopped I stopped going down any further. After several minutes of doing this the bubbles lessened and it actually tried to make a pedal. After about 10 minutes of doing this no bubbles in the MC reservoir then I re-bleed the system and had great brakes! Don't know if I had a bunch of air in the MC and by going down too far I was pushing it past the port and letting it off was just sucking it back and forth OR if I had a seal in the MC sucking in air and working it slowly allowed it to finally seat or swell just enough after soaking brake fluid.... ..
Because moving the car makes it bad but then it’s ok when static I’d suggest you may have a problem with run out in the drums, either they’re oval or the spindles/bearings/hubs are out of true. I suggest this as it strikes me moving the car is pushing the shoes back into the wheel cylinders.
Just for kicks, snap us pics of the inside of the backing plate. Maybe you installed springs wrong or something. Do you have those through the frame fittings? Did you get the same brand master the second time?
Which explains why new masters come with bleeder “caps” these day’s vs bleeder fittings with hoses of the past.
Alchem. Different brand master this time. Brakes are assembled correctly with springs per instructions. The front hoses are on a little L bracket bolted under frame. Master cyl was properly bench bled. All bubbles came out. Used bench bleed kit. Going to give fittings another once over tonight. Make damn sure nothing is slightly leaking and I’m not seeing it.
One thing i might ad, i had trouble with new 39-48 wheel cylinders leaking, the port on the replacements is slightly off center from originals, sometimes letting the fluid bypass the piston in the wheelcylinder. (found that out after researching why in the heck two sets of brand new wheelcylinders would leak sometimes and not all the time.actuall found a few old HAMB threads on the subject via google) they would slowly seep out . MAY NOT BE YOUR PROBLEM BUT FIGURED ID MENTION,( theres a simple fix for that if that is your problem)
Not knowing what kind of car you have, if the master cylinder is under the floor on an early Ford, they can be a real problem to bleed all the air out. It seems you got it fixed but using residual valves on a setup like yours can give trouble and you don't need them. They can cause the MC piston to cover the tiny relief hole in the MC. If it takes an excess of pedal pressure to stop, try going with a 7/8" single bore MC.
JT1930, Confirm that your residual valve is installed with correct flow direction. That would give a great pedal to start then bleed off. Good luck, I hate chasing brake issues.
I think I found it. Brake T fitting for fronts. At first it probably was a hair line until I gave it a little more tightening. Inspecting the flare fitting the center was not centered causing this from the start I believe. Not sure how the fronts were firm when bleeding but guessing it was just enough to let air in more than it wanted to push fluid out. Hopefully this is the culprit. .
I can assume you are frustrated...that can be expected with a non factory mixed brake system that just won't work. Hard to fix over the Internet, but...think more? Just some common sense...maybe. Think about what you wrote, : with just the rear cylinders operating, Fronts blocked off, your pedal goes that far down? So, by then adding also the two fronts into operation, you would think that the pedal will definitely be much closer to the floor. IMO. Each of the 4 cylinders will cause more travel of the pedal, before the brake system stops the car. (What you can think of, is how high would the pedal be if only one wheel cylinder was being used) Your earlier post, you asked if you might need a bigger bore. I would go that idea, far more than thinking a single master is what's needed. I can't see how a dual master will be different than a single master if they are the same bore. That's because I am pretty sure you are bleeding it properly. (Meaning you are experienced)
Have you checked your Wilwood Residual Pressure Valves? I fought a similar problem on my roadster, tried two different master cylinders, bled a gallon of fluid through the system and no change. Finally pulled the RPV's, one was good the spring in the other one had pushed its way through the rubber valve. Replaced them with another brand of valves (tested before being installed) and no more problems.
I got brakes now hamb’ers. I reverse bled with a tool off Amazon. All air out. Help. most of all I think what helped was brake pedal rod adjustment. As I read before the rod shouldn’t be pushing on mc almost like preloading it. Then I’ve also read on here someone adjusting their rod out and gaining firm brakes. I adjusted out some and brakes work great ! Thanks for all commenting and helping out.
The pedal should not put pressure on the cylinder until you put your foot on the pad. Usually a 1/16th inch of clearance or so on the rod is what I shoot for. I have a spring that holds my pedal up to the underside of the floor, away from the cylinder until contact with my shoe.
I originally had done that and also have a 32 style spring holding pedal back. But it’s likes it as is. Maybe this master was bottomed out too far in resting position.
If there's no free play between the pedal and the master cylinder, the compensating port will be blocked, and the brakes will lock up when you drive.
That would do it for sure. A slightly faulty flair on a brake line will pretty much do the same thing allow it to suck in air but not show a visible leak at first. OBTW teflon tape on flair fittings is an absolute do not do. Along with displaying rank amature status it probably prevents sealing more than it helps.
I used Teflon sealant on the brake hoses only. Very little. Because the copper washers they supplied did not fit over the threads. But that is all fixed now.
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