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Im installing new Wilwood calipers on my 69 (non power) and I can’t get a firm pedal. I have scoured through a ton of threads on here and read about alot of struggles while bleeding the brakes.
I have bench bled the MC and used a Motive pressure bleeder in the proper sequence. I’m getting good flow through all bleeders including some air, just like normal, but still a soft pedal. I have raised the back end of the car way up, unbolted the rear calipers and bled them vertically.
I was just bench bleeding the MC for the 2nd time in three days and I noticed as I was plunging it, that it had a slow weep and the rear seal, right where the push rod goes. Would this be my culprit of why I can’t seem to get a firm peddle?
Why did you bench bleed an old master to replace the calipers?
The seals on the master piston have been pushed into parts of the bore they normally do not pass. If there was any corrosion on those spots the seals likely have been damaged. You need to check the bore of the master and depending on what you find, either rebuild it or replace it.
You pushed your screwdriver / master piston in too far and damaged the piston rings.
Lonestar recommends piston travel of no more than 1 & 3/8 inches.
In a bench vise, there is almost unlimited piston travel. (not good)
On the car, the brake pedal / master piston would be stopped by the floor carpet.
Last edited by HeadsU.P.; Oct 18, 2024 at 09:11 PM.
Ok, I installed a new master cylinder and followed all the bleeding procedures. I got a firm pedal, it won’t go any lower than 3” from the floor and the system held pressure under the motive bleeder. However, once the car was started up and everything got hot, the forward master cylinder hardline developed a slow small leak where it attaches to the MC. I have taken it apart and put it back together with the same result. Do you guys think the issue is the new master cylinder or maybe the brake line?
No bolts were installed in the master port, only the plastic fittings for bleeding the MC. The brake line is “newer” however, I did take it on and off several times while trying to achieve a firm pedal with the old MC. It currently seems to be bottomed out in the new MC.
Appreciate your opinion.
Is the new brake line stainless steel?
They have a bad reputation for not sealing.
Every time you took the line on & off the master, you introduced a bubble into the brake system.
Fortunately, it's the front system, easy to bleed again & again.
The copper cones seem to work at caliper connections.
I doubt there is room for one inside the master cyl.
By chance is this new brake-line something you fabricated or is it store bought?
My self, I wouldn't use stainless if somebody paid me for the complete kit.
Too many issues. Common denominator seems to be a flare that won't form correctly due to the harness of the steel.
Brake lines of the past would rust from the inside out and outside in. Hense the reason for stainless.
But in the last decade or so, new brake lines have a coating on them that resist rust, are easily bent and forms better shapes.
Only thing I can tell you is to take a flashlight and a mechanics mirror and peek inside the masters line port. See if anything is obviously wrong with the cast iron-machined flare.
My money is betting on a flawed stainless brake line flare.
Master Cylinder Opinion
