Hopping for some help. I have an on going issue with my brakes. They are traditional manual brakes, with drums on rear disks on front (no booster). Wilwood master cylinder. The pedal continues to go soft. I bleed the air out of the fronts and its fine for a week or so then goes soft and need to be re bled. There is no signs of a leak anywhere and I don't seam to be losing fluid. I changed the front flex lines and that seamed to fix the problem for about a season and a half but its doing the same thing again. I am using regular DOT3 fluid. Is there a chance that the fluid is eating the rubber in the hose?? Any other thoughts? Any help appreciated
The master is under the floor and yes residual valves for front and rear. also a proportioning valve for the rear
If you are only getting bubbles out of the front (?) you are sucking air somewhere in the front system, re tighten everything and see how you go.
I only get air bubbles when bleeding the fronts. The master is a Wilwood unit with front and rear chambers. Each chamber has its own screw on type cap. Is it possible that air could be pulled in past a seal in the cap??
In reading brake threads here lately I've seen a couple guys who discovered their problem was a poor flare or seal. It was letting air into the system in very small quantities, and not leaking any fluid out. I found this hard to believe, but when they found and fixed it, their problem went away. How could more air get into the system without causing the fluid to be removed? Anyway, I would recommend tightening every joint and fitting in your system. And pay real close attention to see if any are seeping. That might be the only way you discover a very minute leak.
I thank you all for your responses. I bled the brakes again this morning and got out at least one full pump of air. Once again the pedal is nice and hard. I have tried re tightening all fittings in the past, so at this point i think I'm going to re plumb from the master out to each wheel. Hopefully I can then put this behind me. Nothing worse than looking at a ride you can't use.
Check the runout on the front rotors. You might not feel it braking but you still could have some. I have experienced air getting into calipers on corvettes with runout. It vibrates the piston when no pedal pressure is applied. Never had it with a single caliper piston but you never know.
I put pressure on the system once for awhile, eventually the leak showed up with one drop. Finally cured my problem. If you are using a vacuum pump, remove the bleeder and wrap it in Teflon tape and make sure the bleeder hose goes straight up from the bleeder plug.
How well are the rear shoes adjusted? Never mind which way master is pointing. Which chamber of master feeds what?