Trouble bleeding rear hyd brake on 67 FLH

[26modelB]

I have been restoring a 67 FLH which required all new rear brake parts. I've purchased all new (repop) parts. Every single part of the brake system with the exception of the brake light switch and the metal brake lines have been replaced. The pedal goes all the way to the floorboard on the first pump & then it starts working. After it sits again for a few minutes, it goes all the way to the floor again. I've done every trick known to bleed them. I've used a Mac tools vacuum bleeder, I've run fluid backwards through the bleeder valve. I've tightened and retightened everything. There are no obvious leaks that can be seen. There is no fluid dripping anywhere. I've run almost two quarts of fluid through it. What am I not doing right?

[Robert Luland]

Your master cylinder is by-passing. Bob L

[26modelB]

Robert,

Thanks for the reply. What do you mean by by-passing and how do I fix it?

[hogchild71]

Model B, insure that the master cyl. has a check valve and seat installed. From the out side,drum and disc brake M/C's look the same. Inside, the drum brake M/C has the check valve and the disc brake M/C does not. Good luck, Fred.

[kg993]

Also check that the shoe stops are adjusted right. Too much slack will let the springs push the wheel cylindar plungers in and pumping will set the shoes back in place untill they are drawn back again.

Kerry

[26modelB]

I double checked the master cylinder and it is the correct one for drum brakes with the check valve. The thing I didn't mention before is that the original master cyl was doing the same thing even after I rebuilt it. So, I bought a new one and still the same problem. I thought about the by-passing thing and it did occur to me that I had the pedal plunger rod adjusted tight against the piston so I backed it off but still had the same problem. The shoe stops and springs pushing against the wheel cylinder idea makes sense. I'll give that a try.

[26modelB]

Kerry,

That was it! The brake shoe stops solved the problem. Perfect brake pedal everytime now. Thank you so much, I've been fighting that for 3 weeks. Thanks to Fred and Robert, I greatly appreciate your input as well.

Mark