Help with brakes.

SlickSublime70

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O.K. folks. Need your help again. The PO told me he had replaced all 4-wheel cylinders, brake shoes (drum brakes all around) and replaced the brake booster and master cylinder. The guy that delivered the car didn't say anything about the brakes. When I first got in the car, no pedal. Goes all the way to the floor. After trying to bleed the brakes all around, still no pedal. After checking with the paperwork from summit, it looks as though he ordered a booster/master cylinder for a 1966 mustang. This is the number that's on the paperwork (SUM-760227). I've already ordered the correct stuff for my Dart. Just wanting to make sure why it won't build brake pressure. I swear, I would never ever let a car go with bad brakes or any safety problems. Pic of booster/ master cylinder he purchased. Also, while bleeding, passenger front and rear bled out fine. Both on drivers side continued to produce air bubbles. as if I had a leak somewhere.

20220731_180216.jpg


20220807_191249.jpg
 
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jazak5

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still could be a bad M/C you said drums all around? looks like you have a disk brake M/C no residual valve ..
 

ACME SS

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I agree with previous post. You can purchase inline residual pressure valves. I have them on my 54 chevy with a corvette MC and booster.
The application of the MC should not matter. I probably put 4 different MC's in a factory five racing cobra replica I built before I found one that had the proper feel without a booster, the reason being the car was originally power brakes but they suggested removing the power due to how light it was. In that case I was playing around with piston diameter, nothing more.
 

SlickSublime70

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still could be a bad M/C you said drums all around? looks like you have a disk brake M/C no residual valve ..
As I stated in my original post, the PO bought and installed a booster and MC for a mustang. Summit racing's website says plainly that this setup will not fit a 1970 Dodge Dart.
 

ACME SS

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As I stated in my original post, the PO bought and installed a booster and MC for a mustang. Summit racing's website says plainly that this setup will not fit a 1970 Dodge Dart.
Well yes and no. I'm big into restomods, etc.. If the bolts line up and everything functions properly as a system then it really doesn't matter what it came off. It usually requires adding parts like residual pressure valves, adjustable proportion valves, etc., that was all I was trying to say.
I get it that you want the correct parts and I would be upset as you are for the same reasons. I can't believe they would sell it like that.
 

72bluNblu

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Yeah, there's some "adaptation" going on in that picture.

You can see in your picture there's an extra bracket to mount the booster to the factory booster mount and linkage. The issue I see with this is that it will change how long the brake push rod needs to be. If the push rod isn't the right length, you won't be building pressure. And then yeah, that's a disk/drum master cylinder so your front brakes will not have the necessary residual valves for a drum brake set up. And the master cylinder bore diameter might not be right either. Whole host of issues there.

Yours
20220807_191249.jpg


Factory Mopar (this one is from a '74 Dart)
IMG_2740.jpeg
 

67Dart273

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Whether it's supposed to fit or not, if the master and booster are a combo (I missed that?) and if the pedal linkage "has been set up" so that the thing will properly mechanically actuate, then if you have "all drum brakes" and IF the master is for drum brakes AKA has residual valves in both outlets, then you should be able to get some sort of pedal. You MUST however "bench bleed" the master to get the air out initially of the master itself. There are LOTS of documentation on the www---do a google search
 

67Dart273

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yeah, that's a disk/drum master cylinder so your front brakes will not have the necessary residual valves for a drum brake set up. And the master cylinder bore diameter might not be right either. Whole host of issues there

I don't believe that is true. Some replacement masters set up for drum may have the same "look"

Even so, lack of residual valves will not prevent a pedal "at least for awhile."

WHAT DO residual valves do? They maintain a small pressure in the system to keep the cylinder cups slightly expanded. This helps keep anything including water or air, from entering the cylinders It is sometimes claimed that it helps "pre pressurize" the wheel cylinders and reduce pedal travel. Not sure if this is really so.
 

AJ/FormS

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Yeah, just about any old M/C can be made to work.
To test the booster, you sorta gotta have a hard pedal to start with.
To get a hard pedal with drum brakes is easy but takes time. You HAVE to start with a bench-bled M/C. Without residual valves this sometimes takes a trick. The fluid likes to return to the reservoirs just as fast as it goes out, so you sometimes end up frustrated with fluid just shuttling back and forth. To prevent this, you gotta pinch the lines before allowing the M/C pistons to return to their parked position which is when the additional fluid gets sucked into the power chambers thru the compensating ports.
Furthermore, there is a chamber between the front and rear sections of the M/C that has to be filled up during the bench-bleeding procedure.
Furthermore, the frontmost reservoir has to be plumbed to the rear brakes.
Furthermore, the front and the rear brakes have to be isolated from eachother. Well they don't for functionality, but that defeats the purpose of having a dual-brake system.

The best way IMO to isolate where the problem is, is to do one of the following;
1) adjust the **** out of the brake-shoe adjusters so the shoes cannot budge, or
2) remove the drums and all the hardware and C-clamp the metal plugs into the wheel cylinders so that they cannot budge.
All the fluid in the system is theoretically thus locked from moving. If the air is out, the pedal will do one of three things;
1) be hard as a rock; this is what you want
2) be spongy; this indicates trapped air somewhere
3) be soft and sinking to the floor, this indicates fluid transfer within the M/C and is bad. You may be able to take the M/C apart and discover why this is happening and even to fix it, on account of those things are pretty simple devices.

The booster will throw a bit of a monkey wrench into the mix, as the Push-rod coming out of it has to be adjusted within a very narrow range.
If it is too short it will not stroke the Piston assembly inside the M/C far enough, and you end up with insufficient fluid travel out of the pressure chambers to affect proper braking; the pedal will reach the floor first.
If the P-rod is too long three things can happen;
1) the C-port will not be opened at the pedal return and eventually your pedal will go lower and lower to the floor
2) the braking will begin too early with respect to where your pedal is and boost will be rather abrupt. This will take time to get used to and different drivers will hate it.
3) if it is much too long, you can break the control valve in the booster, and then you lose modulation. Instead, the booster will full boost with the slightest pedal motion away from being parked.

Somewhere in your system should be a light switch to turn on your brake warning lite on the dash. This thing is operated by a fluid differential between the front and rear systems, to tell you if one end or the other has failed. This device has fluid from both reservoirs dead-headed at either end of it. During the bleeding procedure it is possible to push the valve inside the device from one end to the other. This shuts off the one side so you don't pump brake fluid all over the street after one end fails, and makes sure the other end still functions. And it turns on your dash lite by grounding the circuit. This same lite is used to indicate that the Park/Emergency Brake is on. So if your lite is on, you better know why that is so. Now the point is this, if someone failed to install this device, you need to get one. Or if somebody has removed the valve inside of it, you need to install a different one. Or if yours is stuck at one end and you cannot turn the lite off, you need to fix that.
Now, by this time it should be clear to you that the front and the rear systems are supposed to be independent from eachother, and the only possible connections between them are at the Safety-switch and in the guts of the M/C.
As for the front brake system, they are split usually at the drivers side front frame rail, but both front W/Cs are connected to the same rearmost reservoir. So if one side fails, you will lose Both front brakes.
This makes your description of bubbles at both the front and the rear bleeders on the ONE SIDE ONLY, a real puzzle. My guess is that somebody cross-connected the two systems, and that your car may now have the left side operating off one reservoir and the right off the other; this is bad, so
check it out. But it's just a guess. It could just as easily be, just not fully bled, or,
When you lift off the brake pedal during the bleeding procedure; it is possible that the fluid returns to the M/C faster than your brake return spring return the shoes. When this happens, the M/C may gulp air at the threads of the bleeders. To prevent that I remove the bleeders, clean the threads, and the bleed hole, then anti-seize the threads. Then during the bleeding;
I connect a small clear flexible plastic line between the just-barely cracked bleeder and a small reservoir and elevate the reservoir as high as I can, to a max of say 12 to 15 inches. Now I can see if the fluid is just shuttling in time with the pedal, or if there is in fact air coming out, AND I know it ain't coming from the backside of the sealed-by-anti-seize bleeder.
I find the residual valves handy to slow the return of the fluid.
After the beast is all bled, and the shoes have been properly adjusted, then the brake return springs will control the fluid return. I wouldn't waste time and money installing residuals if yours are not there, AND your W/Cs are not original-type.
 
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inertia

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An M/C is merely a pump, - mounting, and proper pushrod activation are all that's necessary,
How it attaches to the vehicle is arbitrary.
Piston diameter and stroke is only variable.
 

72bluNblu

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I don't believe that is true. Some replacement masters set up for drum may have the same "look"

Even so, lack of residual valves will not prevent a pedal "at least for awhile."

WHAT DO residual valves do? They maintain a small pressure in the system to keep the cylinder cups slightly expanded. This helps keep anything including water or air, from entering the cylinders It is sometimes claimed that it helps "pre pressurize" the wheel cylinders and reduce pedal travel. Not sure if this is really so.

If it's drum/drum the chambers of the master cylinder should be the same size. If anything, the chamber for the front brakes should be larger since they should have the larger wheel cylinders. While we're only looking at the lid, the lid usually matches the chambers. That looks like a disk/drum master to me. Should it still work? Sure, to some level at least. But it's already been established that's not the right master cylinder. And we don't know what the bore is, which could further compound the issue.

Drum residual valves are usually 10 psi. While the system should work and build pressure without them, especially since in this system the master cylinder is elevated above the wheel cylinders, not holding any pressure out there will change how the pedal feels. Especially after the first or second pedal stroke. It might not be "the" issue, but it is an issue. And it could definitely be a contributing issue.

What I see is a bunch of mismatched stuff, all of which could be contributing to the larger problem. Should the OP be able to achieve some kind of pedal with all that stuff? Sure. But why waste the time and effort, since you may end up with a piss poor pedal even when you're done bleeding and troubleshooting everything? I'd be inclined to get the right parts first.

An M/C is merely a pump, - mounting, and proper pushrod activation are all that's necessary,
How it attaches to the vehicle is arbitrary.
Piston diameter and stroke is only variable.

Right, except how it's mounted to the vehicle DOES matter, because it can change the length of the pushrod needed. In this particular hodgepodge, we have no idea if the pushrod is the right length for the added bracket. And the mopar power booster bracket and linkage does change the pedal ratio, so again, it does matter how it's mounted because that can change the bore diameter needed.

The biggest issue I see is that the push rod may be the wrong length, which could cause the no pedal issue by itself. So the OP will either have to go through the procedure to set the push rod length or get the right parts.
 

inertia

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[QUOTE="72bluNblu, post: 1974030968, member,]
Right, except how it's mounted to the vehicle DOES matter, because it can change the length of the pushrod needed. In this particular hodgepodge, we have no idea if the pushrod is the right length for the added bracket. And the mopar power booster bracket and linkage does change the pedal ratio, so again, it does matter how it's mounted because that can change the bore diameter needed.

The biggest issue I see is that the push rod may be the wrong length, which could cause the no pedal issue by itself. So the OP will either have to go through the procedure to set the push rod length or get the right parts.[/QUOTE]

That's why I said proper pushrod activation, - but thanks .
 

SlickSublime70

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O.K. guys, I've read each response and I understand what you all are saying. I really appreciate each of you taking time from your day to help someone you don't even know. I have already ordered the correct parts for my dart. Not sure if the PO bench bled the mc or not. I would be inclined to say no at this point! I will get all of the new stuff installed and go through the entire procedure again. The mc that the po put on is most def foe a disc/drum set up, but the rears are plumbed to the larger side than the fronts. I know that in itself isn't the problem but, I also know it's wrong. I will get it back right! he did have the fronts adjusted so tight that the front wheels slid on the gravel and the grass. It looks like at least he did the new brake set up right. Thanks again to all who responded.
 

67Dart273

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Also, "no pedal" can easily be mistaken for shoes adjusted too loosely. I usually tighten the adjusters up until I cannot turn the wheels, bleed, evaluate pedal "OK" then back off adjusters and ...........ROAD TEST!!!

Shoe adjustment is often easily mis-evaluated with new shoes because they don't "fit" that well "yet" so to speak. Drive it "easy" a few miles then readjust if necessary. If you KNOW the drums are actually new, the following is not a problem, but with worn--turned drums that are too far oversize, the shoes only contact in the center area of the lining, unless the shoes have been ground to fit on an "arcing machine." If I never have to operate one of those dirty things again.........................

post-62228-143142698387.jpg
 

bobsgtx

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Wow! I haven't seen one of those in decades. I wonder how many people that used that machine ended up with lung problems?
 

Murray

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No lung problems here. Standard brake job included "arching" the shoes which meant that the shoes now perfectly matched the arch of the newly turned drums. This led to more progressive and stronger brake feel.
 
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