Technical Brake issue

Here's what I got:

-40 Ford, F100 drums in the front, 40 drum brakes in the rear

-late 60's Mustang Drum Drum Master cylinder under the floor. As far as I know it has residual valves in the MC, because I checked the ports when I got it, a paper clip would only go in a little way.

-I've bled the brakes several times, I get no air at all 4 corners
- all 4 are adjusted to what I would consider "heavy drag" at each wheel.

The Problem: I still have a spongy pedal that needs two pumps to be firm. I pulled the parking brake on and the pedal is nice and firm.....

So, you're probably thinking the rear brakes need adjusted, that could be, but they already drag on the drums.

MY THEORY: I'm thinking that I need more residual pressure in the rear. The MC RPV isn't enough or it's not working. And, maybe there's still some air in there.

Before I buy a 10 pound inline RPV, I thought I'd check here first.

WHAT SAY YOU OH WISE HAMB?

 

OR, maybe I didn't adjust my rear brakes correctly.....

 

Common clear headed thinking: If it is fine with e-brake on, the rear adjustment/shoe fit/ is suspect, not a fluid issue IMO

the lower anchors can cause adjustment problems. One more thing is if you put each shoe into each drum to see if the shoe radius is too small for a worn drum? The shoe would rock like a rocking horse. If the radius is wrong enough, the shoe itself can flex to fit the drum, and that flexing gives a soft pedal.
.

 

The ECI residual valve is the best on the market. I have a pair on my sedan with a 1969 Mustang master and 1940 brakes all around. And if you add a RPV it won't hurt if there is actually already one in the master.

 

Thanks. I'm going to try re-adjusting the rear brakes but if that doesn't help, I'll hit up ECI for a 10# RPV.

 

You have a dual master? One 10# RPV for the front and one for the rear.

 

Yep. But the issue seems to be in the rear, so the RPV in the master seems to being doing it's job on the front side. But if I do have to go to the trouble of opening up the system, I'll put them on both ends.

 

There was a thread on 'rocking and eccentric brake shoes' 2 days ago. Please read thru it, sounds like shoes are not properly indexed at the pins, OR you have shoes that are not properly arced for the drums' cir***ference.

The thread explained the pheno in depth, with drawings and illustrations. Short cut to a "Day at the Beach"!

 

I'm kinda thinking that I adjusted the brakes in the wrong order, now that I read the instructions on a 39-41 lockheed style brake. I'm such a dummy because I have a pair of 46-48 rear brakes and didn't use them.

Anyway, if I adjusted it wrong the bottom of the shoe could be dragging leaving the top with a gap, thusly giving me the pedal I have until I apply the E brake.

 

Buy you books send you to school

 

On my DD had the same problem.Could not figure it out.Sooooooooooooo went to the last area(rear) that I worked on the brakes.Welllllllllll,I screwed up,RR had the shoes on wrong.Long shoe was at the FRONT,and short was at the rear of the drum.Swapped them to the correct position.Now it stops REAL good.
Good luck.Have fun.Be safe.
Leo

 

I had the same setup as you. THOUGHT I had them fully bled. Out of desperation I installed speed bleeders and tried it again. Afterward, the pedal was firm.

 

I adjusted the rear brakes last night and followed the directions as best I could. The pedal is a little better, next step is to bleed the heck out of them. I did find a slightly wet union so it probably ****ed some air.

 

Oh yeah, speed bleeders are a great thing. I installed them on an OT car I put new brakes on, and they work great. I usta think they were snake oil, but now I believe. They might not get bubbles out better, but they make the whole job easier.

 

Well, after bleeding and bleeding and bleeding, pedal is firm. It was a combo of adjustment and air in the lines. Thanks for the input!


Sent from my iPhone using The H.A.M.B. mobile app

 

A good and high pedal really helps the bleeding process, glad you solved it.