Mule 2500 Air in Brake/Master Cylinder

[Bugman]

Last month, the brake line from the Master cylinder leading to rear brake line "T" under the floor board near the seat rusted through. I replaced the brake line, but I cannot get the air out of the system. I bleeded all four wheels and cycled fluid through to get the air out... all the while to be careful not to let the reservoir go down. I pumped up the brakes and cracked the bleeder valve... repeat 10+ times for each wheel. The stroke of the pedal did not improve. I took apart the master cylinder... both seals look good. Inside looks clean. Upon putting it back together, I filled the cylinder as I inserted the actuating piston. I got most of the air out... maybe not all (figuring I could pump it out).

I don't think there is any air in the brake lines... I think there is still some air in the Master Cylinder. My big question is: Is there a special way to bleed the Master cylinder? Pumping up the brakes and hoping the air will come out one of the wheels is not working. Plus, when I crack the bleeder value, the pedal barely moves when depressed to the floor. Very short stroke.

I have rebuilt brake calipers and master cylinders on a few cars in my day, but this problem has me stumped.

I look forward to any suggestions or feedback.

Thanks

[Displaced]

This does sound odd, it sounds like you have put in the time and it should have cleared by now. I'm with you, sounds like air in the master cylinder. Are you using a suction bleeder? Sometimes only a pnumatic bleeder with it pulling the volume of fluid will pull the air with it. That may be the only way to burp the air.

Jon

[Bugman]

Thanks for the advice. No, I have not tried a pneumatic bleeder, but it's worth a try. I'll let you know if it works and what the final solution is.