Brake bleeding (1 Viewer)

[avicenna110]

IIRCC there should be 8 bleeders, 1 on each wheel cylinder,
also are you adjusting both wheel cylinders per wheel?

Yes correct, 8 in total, and I’m adjusting and bleeding all 8.

I bled the rear and it’s already much better, gonna do the front later on today.

 

[avicenna110]

What a PITA this is, I don’t know how my grandpa did this for a living.

I wrapped up for the night at 12:45 AM, after struggling with it for 5 hours. After adjusting the shoes, I bled the lines using the single person method. I put a thin layer of Teflon tape on the threads of the bleeders so air doesn’t get in while bleeding. Teflon tape isn’t sealing the fluid. After the first round of bleeding the pedal was softish at first push but got harder on the second one. So I thought there must be air in the system still. So I started from the first cylinder and repeated the process, again. Now this is what’s happening:

1- first pedal push is hard, but it’s softer than the second and ones after. It doesn’t progressively get harder, just that the first is softer than the rest.

2- there is fluid displacement in the MC, no bubbles , just the level goes up and down slightly when I press the pedal

Are the two above normal for all-drum brakes? I’m thinking (1) is still due to air but I’m not sure there is any air left in the system, I could bench bleed the MC again. (2) can be from fluid getting pushed in the expanding cylinders but I’m not sure.

It’s much better than what it was yesterday after listening to the advice of members here.

Passed mid night and still bonding with this one:

 

[middlecalf]

I think you’re close. I’d put the wheels back on and head to a large empty parking lot and do some hard braking excursions. Then put back on stands and recheck tightness of each wheel (fair bit of drag then back off a click or two) and rebleed. It’s a pain, but once set you’ll be good to go. GL.

 

[avicenna110]

I think you’re close. I’d put the wheels back on and head to a large empty parking lot and do some hard braking excursions. Then put back on stands and recheck tightness of each wheel (fair bit of drag then back off a click or two) and rebleed. It’s a pain, but once set you’ll be good to go. GL.

Got it, and thanks for the advice. What I suspect is happening is the shoes are still not adjusted well so the fluid has to travel more to make good contact, in the process having to borrow some fluid from the MC. Is this possible? Can it happen even if there is no air in the system? I’ll drive it and adjust again, I’m hoping I won’t have to re-bleed but it’s fine if I have to, getting a hang of it.

 

[73FJ40]

Update: adjusted the shoes before bleeding again, they were way way off. Now I’m gonna attempt to bleed.

In terms of getting the air out of the lines and system, isn’t it better if the shoes are not in contacts with the drum? That way they travel more and push the air out. What is the intuition behind adjusting shoes/cylinder before bleeding? I understand that if the shoes are close to the drums they are required to travel less so therefore more effective brakes, but I still haven’t understood the logic behind doing it before bleeding. Doesn’t mean I don’t listen to you guys though.

"isn’t it better if the shoes are not in contacts with the drum?"

Absolutely not! It's best to have the shoes up tight against the drums BEFORE you attempt to bleed. If the shoes don't travel, you are compressing the air in the lines and cylinders the moment you push on the brake pedal. The compressed air then is forced out when you open the bleeder screw, which you close THE INSTANT fluid stop flowing from the bleeder.

Once you have a hard pedal AFTER bleeding, then you back off the adjusters to leave a slight drag on the drum by the shoe

Also, I have six bleeder screws on my '73, since the rear brakes have a jumper tube from the rear cylinders to the front cylinders, leaving only one bleeder on each side of the rear axle.

 

[avicenna110]

"isn’t it better if the shoes are not in contacts with the drum?"

Absolutely not! It's best to have the shoes up tight against the drums BEFORE you attempt to bleed. If the shoes don't travel, you are compressing the air in the lines and cylinders the moment you push on the brake pedal. The compressed air then is forced out when you open the bleeder screw, which you close THE INSTANT fluid stop flowing from the bleeder.

Once you have a hard pedal AFTER bleeding, then you back off the adjusters to leave a slight drag on the drum by the shoe

Also, I have six bleeder screws on my '73, since the rear brakes have a jumper tube from the rear cylinders to the front cylinders, leaving only one bleeder on each side of the rear axle.

I finally understood, thank you!! Clearly explained and it makes perfect sense. Having the correct intuition will help me get it right.

 

[avicenna110]

I drove it for a bit and readjusted the brakes after, with the wheels on this time. It’s much better and stops the car well. I think it could be a bit better but I haven’t bled the lines again yet so hopefully once I do that it’ll be perfect, for drum brakes.

Again thank you all for your guidance and comments.