Sweptline.ORG

I'm getting near the end of a hellish brake job on my 1967 D100. I replaced shoes, hardware, rubber lines, and wheel cylinders on all 4 wheels. Two rounds of successive bleeding and the pedal is still very spongy and almost goes to the floor; won't even really stop the truck. I bled the master cylinder on the truck twice with the pedal, using a brick under the pedal to make sure I didn't bottom out in the bore. Bled the lines at each wheel cylinder with my daughter pressing the pedal, me opening the bleeder and then closing, and then telling her to release the pedal. It's possible I screwed up the MC and it's ruined, but how do I tell if it's that or if there is still air in the lines?

I would suggest bench bleeding the master to get all of the air out, you can cycle the fluid back into itself and get a full range of motion out of the stroke.

Is the master old? U didn't list it as being new. Worn masters have always been the first problem on my swepts.
I have never put a brick under the pedal when bleeding or worried about putting the pedal to the floor. Nor have I ever bench bled one.
Only been driving swepts daily around here since 1978.

IF it is an old master cylinder and they push the pedal all the way to the floor the seals will hit a area where they normally don't and will damage what is left of the seals from old crusty bore. I like his brick idea to avoid going all the way down.

Sorry, I forgot to mention that the MC is new. I initially bench bled it in a vise using a piece of bamboo to depress the piston, but wasn't satisfied that I got everything out. That's when I got the idea to just bleed it on the truck using the pedal; I fab'd two fittings to cycle the fluid back into the reservoir, and used a brick under the pedal just to make sure I didn't bottom it out.

If the shoes are not properly adjusted the pedal will go closer to the floor.

PwrWgnDrvr wrote:If the shoes are not properly adjusted the pedal will go closer to the floor.

Good point!

Yes I was just about to say,
After I did a complete brake job I adjusted the shoes to have no drag at all,
And my pedal felt pretty low.
But the correct factory way to set them up is with just a bit of drag on the drums.

Anyway, driving in reverse and activating the auto adjusters improved things a bit

PwrWgnDrvr wrote:If the shoes are not properly adjusted the pedal will go closer to the floor.

Yep. I normally adjust the shoes to barely contact the drum.... just so
you hear a slight scrape.... and then back off the star wheel by one click
and re-bleed.
John

hobo wrote:Sorry, I forgot to mention that the MC is new. I initially bench bled it in a vise using a piece of bamboo to depress the piston, but wasn't satisfied that I got everything out. That's when I got the idea to just bleed it on the truck using the pedal; I fab'd two fittings to cycle the fluid back into the reservoir, and used a brick under the pedal just to make sure I didn't bottom it out.

Check your push rod adjustment for free-play. If that is not correct, no amount of bleeding will remove air in the system because you would be letting air in with each stroke.

- EM

Very Good Point

John

earlymopar wrote: Check your push rod adjustment for free-play. If that is not correct, no amount of bleeding will remove air in the system because you would be letting air in with each stroke.
- EM

How so?

^^ Same here?

Bucky

Glad it's not just me; I'm curious about that too?

I thought I set up the shoes to drag the drums a bit, but I"ll recheck. Good tips.

PwrWgnDrvr wrote:

earlymopar wrote: Check your push rod adjustment for free-play. If that is not correct, no amount of bleeding will remove air in the system because you would be letting air in with each stroke.
- EM

How so?

Simple. If the push rod has no free play it can and will hold the piston partially open which causes air to bleed out the ports.

- EM

You're missing something on how these systems work, because that's not possible.

Update: pump brake pedal quickly 5-7 times and hold, stiff pedal. Release, depress pedal, and it's soft and goes nearly to the floor.

Bad MC?

hobo wrote:Update: pump brake pedal quickly 5-7 times and hold, stiff pedal. Release, depress pedal, and it's soft and goes nearly to the floor.

Bad MC?

Shoes adjusted too far from the drums.
Takes a lot of fluid to move 4 slave cylinders that distance. Each pedal stroke only supplies a portion of it what's needed. Pumping quickly fills the system before the shoes retract.

Huh. Well, they are dragging a bit, so I can spin each wheel about a revolution, but I'll bump the shoes out a bit and see what happens.

hobo wrote:Huh. Well, they are dragging a bit, so I can spin each wheel about a revolution, but I'll bump the shoes out a bit and see what happens.

Just for giggles, adjust them all too far out and see what happens. This eliminates the "mechanical adjustment" portion of the equation to get a truer picture of what is happening in the hydraulic portion of the system. Of course then you're stuck (no pun intended) with having to loosen the shoes afterwards.

Bucky