BRAKES

[OUREV1]

I did a complete brake rebuild on my '65 and can't get it to keep the pressure built up. I noticed one time that as I'm doing the "pump the pedal several times, hold it, bleed, process", that if I pump up the pressure then let off, I can see the fluid filling back into the brake fluid reservoir. Is this the normal operation, or should this not be happening?
Thank for any help.

 

[unklwedy]

As the brake shoes retract you'll get a little bit of brake fluid heading back to reservoir, but it ain;t a lot. It's time to inspect all 800 wheel cylinders and possibly condemn master cylinder.

 

[OUREV1]

I've already replaced all wheel cylinders, master cylinder, brake lines, and hoses. I would estimate about 1/4" of fluid returns to the reservoir. Normal???

 

[Heirloom]

This is not normal operation. A few things to check, and the reasoning for my ideas:

1. Have you already adjusted the shoes? There are 8 adjusters (one for each shoe).
-if the shoe adjusters are backed out, it wall take multiple pumps of the pedal to move enough fluid into the wheel cylinders to properly engage the brakes.

2. Were you extremely careful to ensure that the correct wheel cylinders were installed in the correct locations?
-There are differences between the wheel cylinders, and installing one or more in the incorrect location will result in air that is trapped in the cylinder and impossible to properly bleed.

3. Did you "bench bleed" the master cylinder before connecting all the lines?
-Trapped air can manifest in a few symptoms. Sometimes (usually) it makes it very hard to build pressure and gives the brake pedal a spongy feel. Sometimes, multiple pumps of the pedal will eventually compress the air in the system and allow pressure to build. Upon release, the air can decompress and push brake fluid back to the top of the system.

My recommendation: Check the shoe adjustment, check the part numbers on the brake cylinders to ensure that everything is in the right place, Disconnect the master cylinder and "bench bleed" it, reconnect the master cylinder and bleed the system until you get 8-10 cycles of bleeding without bubbles. Be redundant and thorough with the bleeding process to ensure you have gotten all the air out.

Hope this helps.

 

[OUREV1]

Yes. That is very helpful. Thank you.
My understanding on adjusting the brakes is to adjust them to where the shoe just starts to engage the hub, then back it off.

 

[3_puppies]

I go tight to the drum so the wheel will not spin and then retract slightly 4 clicks? wheel will spin with slight drag.
do each adjuster 1 at a time.

 

[65swb45]

While you’re bleeding, it’s helpful to have the cylinders adjusted til the wheels won’t turn.

If the cylinders aren’t retracting, there’s less bleedback.

 

[Walkerm916]

Thanks I am having the same issue. That’s some good information never thought to cancel the bleedback issue that way.