A little more brake help please

[Dr. Marneaus]

So the brake battle wages on.

I am on my 3rd master cylinder. I bench bled it and its hard as a rock. Good to go. I am on my 2nd J20 booster. SEEMS to be fine. holds vacuum, the pedal releases kind of slow but it's not too bad. Gonna assume it's okay.

I adjusted the rear drums until they have what feels like even drag on both sides. just a lil bit of drag. You push the wheel with your hand and it stops maybe after 1/4 turn. Without the engine running, pedal feels pretty decent, but still travels a bit far it seems. With engine running, i can push the pedal all the way to the floor, but it is harder than before.

If i take a test drive down the road, I can stop the truck from like 25mph without having the put the pedal to the floor. however if I push harder when stopped, I can get the pedal to the floor. If i stomp, the pedal will go to the floor, the truck slows a bit, and then the rear brakes will BOTH lock up. Previously I had only 1 rear brake lock up on my. Now they both lock evenly and leave even skid marks. I assume this means they are both adjusted pretty close to each other. The braking appears to be acting normal, but it doesnt stop all that well, and the pedal moving so far seems wrong.

what's my next step? The pedal just moves too dang far and isn't super super hard. One line on my prop valve is seeping, but literally to the point where it doesn't drip or anything, it just has a drop hanging from it. I'll address this, but that shouldn't cause the issues I'm having. Somebody said either get the rear drums turned or do new drums.shoes just to make sure stuff isn't out of spec.

I'm so close I can taste it!

[Kenall]

vice clamps.











with vice clamps you can shut off the corners of the wag to isolate where the 'sponge' is.

clamp off all hoses. test for firmness.
if firm, booster and MC are good.

release front clamps, clamp off the hose above the rear axle.
test pedal firmness. if pedal stiff, problem could still be in rear.

clamp off front R or L hose (in turn), repeat test.

[joe]

Any weeps, drips or squirts from any of the fluid carrying parts of the brake system is NOT ok or good'nuf. Fix the obvious issues, re-bleed the entire system before you go looking for other issues you may or may not have. Your Wag is what an early 70's era? When you did the drum brakes you did buy/install a new hardware kit and adjusters right or you relying on 40 year old repeatedly cooked/cooled hardware?
Drum turning is never a bad idea if you have enough metal left to keep them in spec. Having the new shoes arched to newly turned drums is worth the little extra expense if you can find a shop that still does that. Not likely though since the lawyers took over the world. I've never arched shoes on a car at home but have somewhat arched shoes on the rear drum of bikes. It's involved but possible.
Start with fixing any leaks, weeps, then bleed, then do a few mild (low speed) normal backing out your driveway reversing drills to get the final self adjusting function stuff a chance to work. If fixing fluid leaks, manually adjusting shoes, correctly re-bleeding and the backing drill doesn't work. Do a chalk test on the shoes and see if the entire shoe is mating with the drum or just parts of the shoe.
Just thinking out loud here...when you installed the new shoes you didn't mix up the leading shoes with the trailing shoes did ya?

[Dr. Marneaus]

nothing on the rear axle is new except the wheel cylinders and the lines.

The drums, shoes, and hardware were all on this axle when I bought it to do the swap.

Everything worked fine when i still had drums on the front. The truck stopped like normal. The issues arose when i did the disc swap, now nothing is right. Every single part of my brake system is from a 77. Literally including the pedal, all the way to each wheel.

Can anybody confirm that the lines heading from the MC to the prop valve for the front are supposed to be 3/16? and also that the lines from the prop valve to each wheel are supposed to be 3/16?

I haven't really thought about line sbeing the issue, but from whaty I remember before, everything to the front was 3/16, and everything to the back is 1/4"

[Dr. Marneaus]

vice clamps


with vice clamps you can shut off the corners of the wag to isolate where the 'sponge' is.

clamp off all hoses. test for firmness.
if firm, booster and MC are good.

release front clamps, clamp off the hose above the rear axle.
test pedal firmness. if pedal stiff, problem could still be in rear.

clamp off front R or L hose (in turn), repeat test.

good idea. I need more vice grips tho.

[addicted]

nothing on the rear axle is new except the wheel cylinders and the lines.

The drums, shoes, and hardware were all on this axle when I bought it to do the swap.

Everything worked fine when i still had drums on the front. The truck stopped like normal. The issues arose when i did the disc swap, now nothing is right. Every single part of my brake system is from a 77. Literally including the pedal, all the way to each wheel.

Can anybody confirm that the lines heading from the MC to the prop valve for the front are supposed to be 3/16? and also that the lines from the prop valve to each wheel are supposed to be 3/16?

I haven't really thought about line sbeing the issue, but from whaty I remember before, everything to the front was 3/16, and everything to the back is 1/4"

The front lines are all 3/16". The rear is 1/4" until it splits at the axle from the rubber hose.

Did you use everything for the brake pedal; bracket, mount, push rod everything? It seems as though you're not getting a full push.

Oh and vice grips can crush your rubber lines and ruin them from the inside.

[Rich88]

So the brake battle wages on.

I am on my 3rd master cylinder. I bench bled it and its hard as a rock. Good to go. I am on my 2nd J20 booster. SEEMS to be fine. holds vacuum, the pedal releases kind of slow but it's not too bad. Gonna assume it's okay.

I adjusted the rear drums until they have what feels like even drag on both sides. just a lil bit of drag. You push the wheel with your hand and it stops maybe after 1/4 turn. Without the engine running, pedal feels pretty decent, but still travels a bit far it seems. With engine running, i can push the pedal all the way to the floor, but it is harder than before.

If i take a test drive down the road, I can stop the truck from like 25mph without having the put the pedal to the floor. however if I push harder when stopped, I can get the pedal to the floor. If i stomp, the pedal will go to the floor, the truck slows a bit, and then the rear brakes will BOTH lock up. Previously I had only 1 rear brake lock up on my. Now they both lock evenly and leave even skid marks. I assume this means they are both adjusted pretty close to each other. The braking appears to be acting normal, but it doesnt stop all that well, and the pedal moving so far seems wrong.

what's my next step? The pedal just moves too dang far and isn't super super hard. One line on my prop valve is seeping, but literally to the point where it doesn't drip or anything, it just has a drop hanging from it. I'll address this, but that shouldn't cause the issues I'm having. Somebody said either get the rear drums turned or do new drums.shoes just to make sure stuff isn't out of spec.

I'm so close I can taste it!

I'm very anal about getting drums or rotors turned every time I replace pads or shoes. Further, no (reputable) shop will replace pads or shoes without turning or insisting on new metal. And not just as an upsell, but for good reasons. 1) safety, 2) liability, and 3) pads/shoes need to seat, and the newly turned hi-friction surface will do just that. Having said that, still doesn't address the soft pedal. Only air, or very soft hoses can do that. Further, you mentioned locking up only the rears. Whatever the problem, if you can't lock up all 4 then you're not done yet. Its a traumatic event, but I always do it on my first test drive after a brake job.

Anyway, I suspect the proportioning valve.

[joe]

I've never had /felt the need to do a disc brake swap so no idea what size lines are required for your car or the swap brake parts used but fluid system/line integrity "IS" required with juice brakes. FIX THE LEAKS FIRST, then diagnose from from there. Be it body or mechanical stuff and I'm bleeding out from an artery I'm for lets stop the bleeding before we discuss $$$ voodoo surgery.

[Dr. Marneaus]

I'm very anal about getting drums or rotors turned every time I replace pads or shoes. Further, no (reputable) shop will replace pads or shoes without turning or insisting on new metal. And not just as an upsell, but for good reasons. 1) safety, 2) liability, and 3) pads/shoes need to seat, and the newly turned hi-friction surface will do just that. Having said that, still doesn't address the soft pedal. Only air, or very soft hoses can do that. Further, you mentioned locking up only the rears. Whatever the problem, if you can't lock up all 4 then you're not done yet. Its a traumatic event, but I always do it on my first test drive after a brake job.

Anyway, I suspect the proportioning valve.

prop valve is a brand new unit from BJ's. I coughed up the gazillion dollars for one when i have what was supposedly a perfectly good used unit on my hands.

I'm going to put a test light on it tonight and see if the valve is stuck in either direction.

[Dr. Marneaus]

The front lines are all 3/16". The rear is 1/4" until it splits at the axle from the rubber hose.

Did you use everything for the brake pedal; bracket, mount, push rod everything? It seems as though you're not getting a full push.

Oh and vice grips can crush your rubber lines and ruin them from the inside.

Literally every part is 1977 era.

The bracket under the dash, the pedal, the booster bracket, the booster, the master, the lines (home made but made to 77 specs), the prop valve, the rear lines, the wheel cylinders, the calipers, the pads/shoes, the drums and the rotors.

Lol. Yes. Every dang single part of the system is 1974+

I believe I'm getting a full push, because the rears are locking up solid. There is some resistance before i hit the floor with the pedal, but i can push through it if that makes sense? Other than that, i dont feel like i should have to push the pedal 3/4 of the way before it causes the truck to slow down significantly. That doesnt bode well for any emergency situations, even if that last 1/4 of the travel is hard.

[Banchee]

fluid system/line integrity "IS" required with juice brakes. FIX THE LEAKS FIRST, then diagnose from from there.

I have seen you mention this twice here but no response from the OP. Seems like one would fix the known problems then move forward. If there is fluid leaking out, then there is also air and probably moisture leaking in to the braking system to some degree.

I saw that the new master cyl. was bench bleed, but didn't see mension of bleeding the complete system. (But you can't do that until the system is leak free!) I was also wondering if there is more than one hole in the brake pedal lever for the push rod to attach to. Some brake pedal levers have 2 holes up at the push rod. I have seen (and repaired) a couple of cars that someone had attached the push rod to the wrong hole in the lever and they were not getting full travel or full pressure out of the brake system.

Other things to check, flex lines could be colapsed inside if they are old. Rust inside steel lines. Is the engine pulling enough vacuum, where are you picking up vacuum from for the booster?

[Dr. Marneaus]

I will try to fix the weeping line. This involves cutting the line, and splicing in with a union a new line that will hopefully fit. Apparently my flaring skills are not exactly top notch, as is evidenced by the fact that this one fitting is weeping.

Yes. I bled the whole system. Also, this is not the first time i've ever bled brakes so I would like to htink I'm not simply doing it wrong, but stranger things have happened. Also I have had several different people as my helper. I am working on my 4th quarts of fluid through this system trying to get everything to work. Gravity bled, vacuum bled, two person bled.

All brake lines except for the front two going from the prop valve to the soft lines are new. Rear soft line is new. front soft lines are new.

Engine is pulling plenty of vacuum, normally runs around 19" when its warm and idling. I'm pulling vacuum from the front of the carb. the big port. I'm not having a hard time getting the pedal down, as if there was no power. The pedal goes too far, too easy.

Maybe thats how a double diaphragm booster is supposed to feel, but i somehow doubt it.

the brake pedal only has 1 rod coming of of it where the booster rod attaches.

[Tripwire]

As suggested previously (since you have new soft lines) are the drums oversize? ( turned to many times) or the shoes backwards ? - IIRC but not certain the larger/longer one faces towards the front.....

Do you have acess to another similar rig? perhaps some DSPO put in a substitute "close enough" brake pedal assy and thats your issue..... grasping at straws here folks...

[serehill]

Have to agree Andrew

The leak can cause spongyness if it leaks it's getting air. Flairing is a tough trick for me too. Good luck. Make sure the line is square & the flair edges are symetric.

Good luck Bud.

[shosandjeep]

Doc, when you adjusted the rear brakes, did you tighten the star wheel until you couldn't turn the wheel and tire by hand, then back off the star wheel 10 clicks? Old school method, but it seats the shoes. If you only adjusted until you felt drag, you didn't get them tight enough, especially with unturned drums. Just a thought.