Brake Bleeding Problem

[Salvagedcircuit]

I'm in the process of bringing my Comanche back to road worthiness and started servicing the braking system. The brakes worked beforehand but were not that great. For some reason, after all my work I have no brakes at all. Even after trying to properly bleed everything including the prop valve, I have extremely soft brakes.

 

Initial Condition:

1. Front rubber hoses rotted and chipped, the rear rubber brake line is in similar shape.
2. Hard brake line looks stock and has the armored metal appearance. The hard line looks in great shape somehow even after 34 years.
3. Rear brake drums are within dimensional specification and do not have much wear
4. Rear drum shoes were warn but usable. passenger side asymmetrically warn
5. Rear passenger side parking brake miniature cable snapped.
6. Front brake pads were about 50% life, front discs not that warn
7. Master cylinder lid very rusty
8. On first opening of lid, inside fluid looked brown and muddy. The smaller compartment was bone dry and had a lot of brown residue.
9. Rubber gasket had fine particles and mud like residue on it. rubber gasket was pulled out.
10. Some rust flakes from the lid fell into the fluid on first opening even though I tried to avoid that.
11. Brake booster very rusted externally

 

Procedure:

1. Replaced all rear drum brake cylinders and shoes
2. Replaced all drum brake springs and hardware
3. Brake drum cylinder forks not included in new brake cylinder kits. Original ones were bent but I could not find replacements.
4. Tried to replace rear rubber brake line with the block end that mounts to the rear. Rear axle hard line that threads into the rubber cable block was stuck and started to feel like it was going to shear so I stopped before damage. Re-attached rear cable as it was previously.
5. Replaced front disc rotors and pads, front passenger & driver rubber cable, and driver caliper. Driver caliper bolts were completely wrong and previous owner used plastic spacers!
6. Cleaned out master cylinder compartments with paper towel and simple green. Added new DOT3 brake fluid
7. At this point, some fluid was already lost from replacing rubber brake lines.
8. Bled brake lines from passenger back, then driver back, then passenger and driver front. Repeated process for prop valve and put key in ignition to turn on dash light. Light never illuminated. I tried several times.
9. Bled brakes with 2 people. The stop-start method. I repeated the entire process a second time to try to get the dash light to illuminate. It never illuminated. During the bleeding process, when pumping the brake, I only seldomly was able to push the pedal all the way to the floor for that second stage engagement. A few times It was hard to pump the pedal, but it would not stay that way.

 

At this point I don't know what has failed in my brake system. I am under the impression that there is most definitely fine particulate in my brake lines and my master cylinder or brake booster may be clogged or has been for a long time.

My plan right now is to disconnect all the components in the braking system, use a large air compressor to blow out the hardline and just start over. I will be replacing the hardline on the rear axle that would not loosen from the prop valve.
I bet the prop valve needs a rebuild too, but I don't know if those components are still available anymore.

 

What could be causing my problems? Clogged prop valve? Damaged brake booster? I read something about a leaky booster / check valve. Is that possible?

I don't mind replacing the brake booster and master cylinder now as they are likely 34 years old, but I'd like to use new mopar parts. I have been jaded enough by the dorman / crown / clone part quality of the coolant tanks. I don't want a life-saving critical part made to such poor quality standards.

Thanks for any input!

[howeitsdone]

Typically the booster isn’t working properly anymore when this happens. I have the same issue and the booster has been determined to be at fault. It’s not building the right pressure anymore. Although, the master should never be empty and sounds like that may have been the case when you cleaned it. Not sure if that introduced some unwanted air. 
 

Plenty of write-ups on upgrading to WJ boosters that are dual diaphragm. But isn’t without some work. 
 

The rear prop-valve parts aren’t going to be found anymore, but it’s perfectly fine to remove if you’d like. Will require a prop valve at the master. 

[Salvagedcircuit]

23 minutes ago, howeitsdone said:

Typically the booster isn’t working properly anymore when this happens. I have the same issue and the booster has been determined to be at fault. It’s not building the right pressure anymore. Although, the master should never be empty and sounds like that may have been the case when you cleaned it. Not sure if that introduced some unwanted air. 

Thanks for the input!

Strangely, I hooked up my vacuum gauge to where the brake booster was connected and I believe I read somewhere in the low 10s. I have to check my photos. Considering the terrible shape my vacuum lines are in, I was surprised.

 

Currently, I am leaning toward installing a WJ booster + master setup and a wilwood prop valve.

It just bugs me that I don't quite know whats troubling my brake system.

 

[howeitsdone]

If you’re pulling a good vacuum then it could simply be air in your master or a bad hose unless you can spot a leak. I sometimes forget bad boosters make it hard not soft. 30+ years does weird things to these brake systems. 
 

I’ve used a vacuum bleeder, 2-man crew, and now I’ve got speed bleeders. Short of replacing the booster and master I’ve done all I can as well to fix it.

 

Maybe someone with any further knowledge will respond tomorrow. Good luck!

[md87]

Doesn’t seem likely for your situation since you only replaced one caliper, but when I replaced both calipers, I mistakenly put them on the wrong sides.  Maybe check that your bleed screw is at the top of the caliper.

[Salvagedcircuit]

7 hours ago, md87 said:

Doesn’t seem likely for your situation since you only replaced one caliper, but when I replaced both calipers, I mistakenly put them on the wrong sides.  Maybe check that your bleed screw is at the top of the caliper

Thanks for this info. I double checked and the bleed screw is at the top of the caliper. It is not that uncommon for parts to be mislabeled in boxes from autozone and parts stores.

[md87]

I was hoping maybe there was a quick and easy fix, but I guess not.  I would think that particulate would not cause no brakes since the particulate would not compress like air (although I suppose particulate could cause some seals not to seal).  Like someone posted above, a bad booster should make the brakes hard, not soft.  I would think there's a leak, air in the system, or a bad master cylinder.  I'm not sure if you would need to do a bench bleed on the master cylinder.