Another "brake help" thread...

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swisswill

swisswill

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I've scoured this forum and have done a lot of initial diagnosis based on what I've read, but I'm still dealing with bad brakes, real bad. Here's a breakdown of what I have, and what I've done.

'76 Dart Sedan, factory manual brakes, 7 1/4 rear w/ 10" drums. Discs up front that have been converted to new '82 Dip calipers mounted on the rear (hose at bottom, bleader at top) with speed bleeders on the calipers; need a set of speed bleeders for the rear but they are M6 and not available at the local parts store. New 15/16" MC from Dr. Diff. New pads/shoes/flex lines from Bergman. Rebuilt the drums with new everything, springs, wheels cylinders, shoes, etc. Everything is new in the system but the actual drums, rotors, and combo/proportioning valve.

Feels like almost 90%+ bias to the rear brakes for stopping; I know the rears lock up and I've never gotten the fronts to lock up; at least 10x more brake dust on rear wheels than front. When I pull the drums off, everything is covered in black brake dust and dust falls out of the drum. Almost no brake dust on the front wheels, but the rotors are shiny so I know the calipers are doing something, but not much. Rear brakes are awful loud, squealing/screaming/screeching, drives me nuts. Also sticking occasionally and surging, such that if I let me foot off the brake pedal, the car may not move, it may move slowly, or it may surge because of brakes sticking, then not, then stick, then not, repeating. Perhaps the drums are out of round? But there must be more wrong. TONS of pedal travel before I feel the brakes kick in. I have to pump 3-4 times in order to get what feels like a decent pedal. I've bled the brakes more times than I remember. Originally bench bled the MC on the car, but this weekend I pulled it off the car to actually bleed it on the bench. I pulled on the parking brake cable to ensure it was not creating tension, didn't seem to be. Parking brake system is missing the intermediate cable and the cable to the pedal (if anyone has one, I'll take it). In other words, parking brake levers are not connected to the pedal. No geysers out of the MC when releasing the brakes. I've adjusted the rear brakes multiple times such that I hear a slight rub of the shoes to the drums when I spin the drums. Fluid was flushed after I did the new MC, rear brake rebuild, and new calipers. I don't have a gauge set to test the pressure into and out of the proportioning valve so not sure if that's working right, and can't find details on testing otherwise. Cass has confirmed rear drums are assembled correctly, other than the top washer being upside down but that shouldn't hinder anything. Cass also said the fronts look good, except the drivers brake hard line and the flex line connections are upside down. I have some CopperNickel coming tomorrow and will reorient. He pointed this out saying it could kink the flex line. No evidence of that. Also, no evidence of fluid leaking anywhere. MC is always full, no spots on the ground unless I'm going through a bout of bleeding.

What am I missing? Any other ideas? My thoughts at this point are either a bad MC, proportioning valve, or both. MC is new though. Thoughts? Not sure how to test without a gauge set and that's not something I've seen at local stores. Thank you everyone.
 
I'm no brake system expert but I have a few thoughts. I had a car with a replacement MC that had no residual valve in it and it resulted in excessive initial brake pedal travel. Also, you would think the prop valve would resolve the front to back issue as that is what its for. Do you have a procedure of setting up the bias?
 
Crossed lines into the Combination valve?
OR
the front brakes just not working.

>You must have a high, hard pedal, on the first pump. That proves the system is free of air.
>with the car stopped, IF it takes multiple pumps to achieve a hard pedal;
1) the rear shoes are out of adjustment and/or
2) the front pistons have retracted too far.
>The Compensating port must be open with the pedal parked.
The REAR-most chamber drives the FRONT brakes thru the TOP of the C-valve, which is just a Splitter section.
>At the Caliper brackets, the calipers must be free to slide back and forth on their "ways". and the Pads must be semi-floating the brackets. and, the two pads must sit flat on the rotors.
> the caliper-pistons and pads, have to be parallel to the faces of the rotors. If they have to be twisted by the force of the brake fluid, that takes pedal-travel to accomplish.
>Finally, the rotors better have the right bearings in them, and them adjusted correctly, to keep them concentric to the not-bent spindles. This is actually where it starts, cuz if your pistons are getting knocked-back into the calipers, by rotating parts, that's gonna take more than one pump, just to advance them, and if the car is moving, every time you go for anther pump, the pistons retreat, ot get knocked back
>Multiple pumping of the brake pedal, speaks to excessive pad/shoe travel; usually in the rear system, but in your case, I'm betting on it being in the fronts.
>Brakes sticking on, points to the fluid NOT returning to the M/C.
My usual guess would be a residual valve still in the M/C, or in your case, more likely is that the PowerPiston inside the M/C is not returning far enough towards the firewall, most likely because of a misadjusted and too long pushrod , or could be a pedal not parking high enough, or a faulty C-Port. At rest, the Compensating Port HAS To be open.
>intermittent sticking-on, can also be a kinked front flex hoses, while turning.
>At the back, noise indicates something is wrong there, figure it out.
Btw modern w/c's do not actually need the hold-off/residual valve in the M/C, altho, leaving it there hurts nothing, so long as it is assembled correctly.
As for Oval drums; I doubt that is your problem.

This list may not be complete, just all I can think of just now.
My best guesses are in bold

Happy HotRodding
 
The proportioning valve is adjusted by bleeding the brakes in the proper order- passenger rear, drivers rear, passenger front, drivers front.

It sounds like your rear brakes are dragging and overheating. If it’s both of them, it’s possible that the rear brake hose that goes from the chassis to the axle is partially collapsed internally. That can hold the brakes on.

Get rid of the speed bleeders, they’re awful. As someone that often has to bleed brakes by themselves I have tried them because it seems like a great idea. In practice, those damn things never work right and typically result in a leak or air still trapped in the system.
 
72bluNblu said:
Get rid of the speed bleeders, they’re awful. As someone that often has to bleed brakes by themselves I have tried them because it seems like a great idea. In practice, those damn things never work right and typically result in a leak or air still trapped in the system.
Click to expand...

this. 1000% this.

i curse those wretched things
 
  • I'll pull the speed bleeders. I literally put them on three days ago so they are not part of the problem, but I hear you.
  • CV lines are not crossed, I've checked multiple times. Also haven't touched the CV except to replace the front drivers hard line from the CV.
  • I've bled the brakes so many times, and every time but the most recent (after the off the car bench bleeding and speed bleeder install) it's been in the correct order. Most recently was just the fronts again, but worth going back through to be sure.
  • Caliper retainer clips are torqued to 15 ft-lbs per the FSM.
  • Retainer clips, anti rattle springs, rubber bands are all new (are rubber bands necessary? I doubt that's my issue up front because they don't touch the calipers).
  • Front pistons might be retracted too far, calipers are brand new though. Any way to test?
  • Rear shoes have been adjusted multiple times, every time I pull the drum in fact because I'm burning through the shoes. But I'll do it again.
  • I'll inspect the flex lines again. These are braided lines and not likely collapsed being they too are brand new from Bergman. Being braided lines, anyway to know for sure if they are collapsing? I could see a kink in a braided line causing an issue, but seems like I'd actually see the kink. I'll get the car on ramps so I can see the lines while I cycle the suspension and steering.
  • I do not have a high hard pedal at all. In fact, I'm 75%-ish stroke before I feel a level of resistance that indicates (to me) brakes engaging. Then a couple more pumps and I have the kind of pedal I expect.
  • Looking at the trouble shooting flow charts in the FSM, they point to proportioning valve (not new), rear brake hardware being weak (maybe, but new), frozen pistons/contaminated linings (maybe, but new), and then of course air in the line (maybe, but I've bled everything multiple times).
All that said, I'm at a loss as to why I have almost no pedal w/o at least 3 pumps, super loud rear brakes (once they're pumped up), huge amounts of brake dust on the rear with virtually nothing on the front, and occasional rear brakes sticking. I'm curious, is there a way I can test to make sure the front calipers are sliding? Is it dumb to pull a pad and hit the brakes? Is it dumb to pull the drum and hit the brakes to see how/if the shoes are retracting? The FSM shows a great set of gauges to test pressure in and out of the CV, would love to do that but can't find anything that looks like I can T into the lines. Any other ways to test the MC/C-valve?

Thank you for the feedback so far.
 
Is your brake warning lite on?
Is it functional?
Prove it works, by continuity-tester, and if the Safety switch at the Combination valve is grounding that light, then you will have to re-align the Shuttle valve. If the shuttle valve has been forced to one side by your bleeding efforts, and it has stuck there, and if it has moved towards the front brakes, it will shut them off! which is by design.
But if the valve is centered with NO-continuity to ground, then we can proceed;

Not an A-body switch but you get the idea. Here the shuttle valve is called the "pressure differential valve".

1728955865613.png


There is a way to divorce the hydraulics from the mechanical system; but you're not gonna like it.
I'll tell you anyway.. It goes like this;
Part-1; the front brakes
1) Get all four corners up, the wheels off, and all the brake hardware off
2.) C-clamp the caliper pistons into the bottom of their bores
3) Remove from the w/cs ,the shoe actuators, then push the w/c pistons into the bores flush with the bodies, then C-clamp them in there so they cannot pop out.
4) pump up the brake pedal until it is high and hard to a moderate effort. Some pedal motion is used up by the workings of the C-port, but not more than one inch, and as soon as that C-port is closed, the pedal should instantly get hard.
5) while there, and without taking your foot off the pedal, add and subtract a little pressure looking for sponginess. If you find it, fix it. If you don't, proceed
6a) take your foot off the pedal and wait at least 5 seconds for the fluid to return to the Master; then press the pedal. If it is still high and hard, then your hydraulics are fine. But if the pedal goes soft again, you have air in the system or crappy flex-lines, or a faulty master. Proof is by process of elimination.
6b) proving the lines is by observing them
6c) proving the air in the system is by observing roiling at the Compensation-Port. If you get a geyser upon release of the brake pedal, there is trapped air, acting like a spring, and forcing fluid back into the master. CAUTION, brake fluid attacks paint, so take steps to contain the geyser, I'm not buying you a new paintjob!
6d) if b an c above are good, that points to bad M/C.
Part-2
10 if everything turns out good, now you can be sure that the hydraulics are good.
11) the next place I would look is to a flexing caliper. I used to have a machined metal block to lay in the caliper, then pump up the brake, to observe the caliper flexing and prove seal retraction is working. The pedal should get hard, and upon release, the piston should be retracted back into the bore, just a few thousands of an inch.When you are satisfied, C-clamp it back in, then move to the other side . When satisfied;
12) get a prybar and figure out how to prove the rotors are properly seated on the spindles. a couple of thousands of movement at the OD are acceptable, but not much more, and they should spin freely, and smoothly. What I'm looking to prove is that the bearings are sized right and that the outer races have been properly seated . You can't have a floppy rotor that keeps loosing it's adjustment.
13) working one side atta time,
13a) Take the pads to a surface-plate and see if the friction surfaces rock. Rocking is unacceptable.
13b) Put two of them together and see if they rock, face to face, which would be unacceptable.
13c) C-clamp two of them together, near the center point. Then with a caliper, make sure both ends measure within a few thou of the same.
13d) fit the pads into the bracket, and see if they move back and fourth fairly easily, to and from the rotor. Clean out the rust as may be required, and try again. When you are satisfied, cuddle them up to the rotor
14) install the caliper making sure all hardware is factory and not bent. pump up the pedal. looking for high and hard. If it is not, it can only be that the caliper is NOT running at 90 degrees to the rotor. Have a friend operate the pedal, while you get eyes on the caliper. if the piston does not contact both ends of both pads simultaneously, then you will see the caliper do a little funky dance, with increasing pressure. If this happens, something is bent, be it the caliper or the bracket; find it, then replace it.
14b) After you are satisfied, take it apart and C-clamp the piston back into the bore, then move to the other side, with the remaining pads, and repeat.
14c) when you are satisfied, reassemble the front system and go look for a high hard pedal.
14d) as said earlier, some dropping of the pedal is normal; up to maybe one inch, as the C-port has to be closed first.
Part-3
the rear brakes. one side atta time
1) relax the parking brake!
2) fit the shoes to the drums. If you can rock them on the brake surface, they are gonna take a long time to break in. If the shoes stick out of the drum laterally, they are wrong
Notice that there are long shoes and short shoes; each side of the vehicle gets one of each.
2a)Most likely you have already installed the parking arm onto the longer rear shoe , I think the pin only fits one way.
2b) the rest you are already intimately acquainted with.
3) since you have noise, look into the drums, at the mounting flanges; witness marks there point to the shoes being too wide or you have excessive axle end-play
4) The Park-brake struts and self adjusters, are side specific. Make sure that they have not been swapped side for side. I forget which adjuster goes on which side but if you get them backwards it's hard to adjust them, and I suppose, they would unwind during use. IDK that, cuz I've never done it, lol. IIRC the adjusters are marked "L" and "R".
5) When yur done installing,
the shoes have to be resting tightly on the anchor pins. If they are not, check that the Parking Brake struts are fully retracted. The parking brake cables have to be adjusted every time you install new shoes; unless you never use them, I suppose, lol.
6) adjust the rear shoes tight to the drum, then back them off a few clicks .
7) the Parking brakes try to adjust themselves every time you back up with the brakes applied. If I had your problem I would defeat this mechanism until this problem is resolved. This is as simple as removing the cable and the spoon.

Once again, Happy HotRodding
 
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If the later [ 1982 ] discs have larger pistons, then you may need a larger m/c than 15/16". Obviously, the larger the caliper piston diam, the further the m/c piston has to move [ pedal travel ] to provide braking. You may have a mismatch of parts.
 
AJ/FormS, just to make sure I got this: pull the calipers and c-clamp the pistons. Pull the push rods from the wheel cylinders and c-clamp the pistons. Hit the brakes, then process of elimination per your outline. That makes sense.

Bewy, same size piston, but good thought and had me digging.
 
Bewy said:
If the later [ 1982 ] discs have larger pistons, then you may need a larger m/c than 15/16". Obviously, the larger the caliper piston diam, the further the m/c piston has to move [ pedal travel ] to provide braking. You may have a mismatch of parts.
Click to expand...

Keep in mind that calipers merely relax, movement of a few thousands if not "knocked back" by a bent rotor.
The difference in fluid volume between the 2 diameters is minimum.
Once bled, the M/C just adds pressure to an already full system.
Cheers
 
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swisswill said:
That makes sense.
Click to expand...
Remember to check your Brake-warning system FIRST;
and prove the shuttle valve is correctly centered.
There are at least two other guys here that suspect the C-valve is the source of your woes.
>That Dash light is also grounded by the Parking brake. If your cables are known to not be seized, then pulling the handle is supposed to turn the light on. But if the light is already on, hop out and pull the wire off the C-valve, which should then shut the light off ...... unless the Park-Brake switch is already activated. This will sortof prove the system is working.
>Because of these factory shenanigan's, I just find it faster to ohm out the switch directly, and when the valve is centered there will be no continuity to ground thru it. See attached image in Post #7. Here you can see that properly centered the spring-loaded plunger on the end of the brake-switch is NOT touching anything and so the light remains off. But if the shuttle valve moves even a tiny bit, the plunger will ground back to the battery, thru the valve and valve-body, turning the light on..
>And you can also see that if the valve should travel all the way towards the front inlet, it will shut off fluid travel into the front brake system.
If this happened while you were bleeding the front brakes, then you can bet that the front brakes have NOT yet been bled properly...... unless maybe you bled the fronts first, lol.
The same happens if the shuttle travels all the way to the rear.
>Centering is by cracking the inlet fitting on the opposite side of the non-working system, and gently pressing the brake pedal until the light goes out. then tightening the fitting back up.
>Now, if you do not have a high hard pedal after centering the valve, I would suspect the front system will need to bled again ( but it could possibly be the rears). Normally the shuttle will stay centered, unless you pump really hard, like as you would in a panic braking situation. And if the light does come on, you now know how to turn it off by centering the valve.
>Once the system has been bled, you can see that both sides of the valve get the same pressure from the M/C, and the valve should stay centered.
 
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The extra pumping, loud noise, and bunchas of dust is crazy.
I once had installed a rear wheel cyl pushrod and missed the shoe.
The result was the pushrod slid beside the shoe, forcing the shoe outward against the side of the drum, when pedal applied, creating lotsa noise.
Can you just check the pushrods are where they should be in the shoe.
Maybe a few pix might help.
You won't get "pedal" till all pads and shoes are in full contact with the rotor/drums.
Those pumps should be moving something that stops when you get pedal .
Bent a disc pad that wasn't in right too.
 
Bewy said:
If the later [ 1982 ] discs have larger pistons, then you may need a larger m/c than 15/16". Obviously, the larger the caliper piston diam, the further the m/c piston has to move [ pedal travel ] to provide braking. You may have a mismatch of parts.
Click to expand...

Not even close. The 2.75" pistons calipers work great with a 15/16" master cylinder. Been there, run that, nothing at all wrong with the combination and it is an IMPROVEMENT over stock A-body 2.6" pistons.
 
Inertia said:
Bent a disc pad that wasn't in right too.
Click to expand...
Yeah, I've seen that come in thru the doors a time or two.
Which is why I included how to spot it in the Diagnoses.
Plus bend pad holders, bent sliderpins, worn caliper ways, collapsed hoses acting like check-valves, lotsa seized pistons, rotors with hot-spots that vibrated the heck out of the steering wheel, control arms nearly falling off, and one even did on a Chevy truck!
That last one actually made my day. It came in on a flatdeck from 50/60 miles away, just to have me work on it. The owner trusted my work, by reputation, more than a local shop to where it happened, in a big city with some 600,000 residents and probably dozens and dozens of qualified brake shops. Yeah, to say I was tickled is an understatement.
I'm just a guy out in the boonies, doing his thing...... and then this happens; wow.
 
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AJ/FormS said:
Is your brake warning lite on?
Is it functional?
Prove it works, by continuity-tester, and if the Safety switch at the Combination valve is grounding that light, then you will have to re-align the Shuttle valve. If the shuttle valve has been forced to one side by your bleeding efforts, and it has stuck there, and if it has moved towards the front brakes, it will shut them off! which is by design.
But if the valve is centered with NO-continuity to ground, then we can proceed;

Not an A-body switch but you get the idea. Here the shuttle valve is called the "pressure differential valve".

View attachment 1716315797
Click to expand...

All good info from A.J., and as he mentions, the illustration above is not Mopar, it's another breed .

I've never seen that type of valve on a Mopar, thankfully, they're a ***** to have with line-lock, as they need to be centered everytime you use the line-lock, - to shut off the warning lite, most just have the wire pulled off, so warning function is disabled.

Here's a pic of the Mopar Imbalance Switch, - which are self-centering, when the imbalance/pedal/line-lock is released, the lite goes out. The two opposing springs center the shuttle when there is no pressure in either system.
Cheers.

IMG_20231105_192947.jpg
 
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AJ/FormS Just a few minutes this morning to diagnose but found the brake light wasn't working. I spent some time to get it working then disconnected the parking brake wire from the switch to remove that variable; I don't have an intermediate cable anyway so the pedal isn't doing anything but triggering a light. Once the light was working I found that an initial hit to the brake pedal, regardless of the pressure I use, turns the light on. The second hit turns it off and the pedal starts to firm up. If I understand correctly, initially I have low pressure to the front brakes, the shuttle valve moves and sticks, probably blocking fluid to the front brakes, then resetting after I hit the pedal again, everytime. I'm open to your thoughts, but it seems like I have to replace the c-valve, prior to moving forward. In my mind, I clamp the caliper pistons and wheel cylinders, but keep getting a stuck shuttle valve on the initial hit, I'm going to struggle getting the system straightened out. Let me know your thoughts on next steps given what I've found so far. Thanks!
 
I'm thinking

Give the pedal a hit to turn the light on, then back off the pedal and wait.
When you lift, the fluid should return to the master. and the springs inside the C-valve should center the shuttle valve, thus turning the light off. Give it a few seconds.
If this happens as above then;
First of all, the fact that the light turns on and off indicates that the C-valve is in fact working!
Secondly, Ima thinking;
one of two things is wrong,
1) one side of the master is not pumping fluid, or
2) one side of your system from the C-valve onward, has excessive fluid-travel.
I'm going with Option #2.

Here is a cutaway to help you envision how the M/C works.
In this image, the ports labeled "inlet" serve double-duty as compensating ports.
Notice that the "piston" on the right is NOT connected to the piston on the left.
The two pistons are supposed to be hydraulically coupled by brake fluid in that left chamber. Bench bleeding is essentially designed to fill that chamber.
Notice that the piston on the right has a stub-shaft integrated to the front of it. If the chamber is not filled , then that stub moves to the left and pushes that left side piston by mechanical action. This takes extra pedal travel.
The left side piston activates the rear brakes. If the shoes are not adjusted up tight, then that piston will have extra travel. Notice where the "inlet port" to that front chamber is.
If you make multiple stabs on the pedal, each time the power piston returns, more fluid will enter the chamber, and eventually, there will be enough fluid in the system to activate the rear brakes.
But, when you release the pedal, and wait, the shoe return springs in the rear brakes, will pull the shoes back onto the anchor, which will force all that fluid, back into the reservoir. and so, the next time you apply the brakes, you're back to multiple pumps.
I think, this situation can only exist if
a) that interchamber is devoid of fluid, or
b) the front brakes have excessive air in them.

As you can see, that inter-chamber can get fluid from both ends. So then, as long as the power-piston is returning fully toward the right, fluid will enter it. And whenever the power-piston travels past the "inlet port" on the left, fluid will again enter the port.
But look closely
If the left piston passes the port, there is nothing to keep the fluid in the inter-chamber from rushing out into the front reservoir.... which would allow the right-side piston to move forward and go into mechanical mode. Instantly, there would be a pressure differential in the lines and the "combination valve" would turn on the light.
Therefore, the key here, IMO, is to readjust the rear brake shoes to limit the wc piston travel. But of course, this also means to eliminate air in the lines, which is what the C-clamp system is designed to discover.

All that to say, what others have implied, is that your rear shoes HAVE to, at rest, be sitting on the top anchor-post, which means that the Parking cable must be fully relaxed.

Good luck

1729099828761.png
 
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