RF brake locked up. Why?

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RichB

CherryCuda65
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Returning from the transmission shop with my newly restored (all stock) 1965 Barracuda I decided to drive down to a gas station and get gas. About a mile away the brakes started to fade out. Near the gas station smoke started coming out of the right front fender. At the gas station I saw that brake fluid had sprayed around the right inner fender well area. When I then tried to move the car I found it was locked up and the rear tires squealed. I called a tow truck and while waiting for it I found the RF Wheel brake had then freed up.
I have not yet started to take it apart. I had DOT 7 fluid in it.
What do you think happened and what do you think will have to be done and replaced?
 
The rubber hoses can fail internally.

If that happens a 'flap' from the degraded inner lining can act as a one way valve, letting pressure in, but not out.

Over time, the stored inner pressure can relax.

I would start there.
 
I just dealt with this very problem yesterday. I’ll post pictures showing internal
A8EBB561-C444-467E-A186-82E184738727.jpeg
collapse of the hydraulic hose.
 
Check the return holes in the bottom of your Master cylinder. I have had debree / rust plug up those holes and cause the same situation.
 
Returning from the transmission shop with my newly restored (all stock) 1965 Barracuda I decided to drive down to a gas station and get gas. About a mile away the brakes started to fade out. Near the gas station smoke started coming out of the right front fender. At the gas station I saw that brake fluid had sprayed around the right inner fender well area. When I then tried to move the car I found it was locked up and the rear tires squealed. I called a tow truck and while waiting for it I found the RF Wheel brake had then freed up.
I have not yet started to take it apart. I had DOT 7 fluid in it.
What do you think happened and what do you think will have to be done and replaced?

It's also possible that you have a metal brake line to close to the exhaust somewhere.
(Just something to keep in mind)
 
First, WTH is DOT7 and why do you think you need it? Sounds like you had a leak and it got on the shoes. That will cause your problem.
 
You say everything is new. Does that include lines, hoses, etc.? It sounds like something sprung a leak, and brake fluid got inside the drum. Possibly a blown out wheel cylinder? Top off the master cylinder and have someone press on the brake pedal while you are at the wheel looking for a leak. If you don't find a leak, then replace what needs to be replaced and have someone step operate the pedal slowly up and down (leaving 15-20 second intervals without brake pedal pressure so you can test spin the drum).
 
You know the story: Everything is new, but not everything is necessarily good... Since they're drums,and I'm assuming everything bled out fine- (would SORT OF rule out rubber line collapse) I would make DARN sure you've got them adjusted out as far as necessary, because if the pistons have to travel too far out in the brake cylinders, they can actually **** and jam at the end of the bore, locking the brake. Now that I think of it, make sure your self-adjusters are on their correct sides! If not, they could actually change as you drive, causing gradual loss of braking, and then the piston hanging up...
Or a wrong (RHT/LHT) adjuster on the wrong side.
 
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I have seen where brakes that were assembled from "a picture in the service manual" were actually done the same on both sides, instead of reversed on the opposite side, and showed similar symptoms.
 
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If you put DOT 7 in it, you should probably have someone that knows brakes work on it.

Imma wager that the shoes were over adjusted and expanded with heat, which caused them to drag harder, get hotter, etc until they cooked.

But I don't know drum brakes that well.
 
It shouldda had a horrendous pull to that side. If it didn't then check the other side;they mustabin BOTH dragging. And if that is true, it points to a non-functioning Compensating port, due to the M/C piston not parking far enough to the rear.

But if in fact only the one side was dragging, then it could be for several reasons, as already mentioned. Or even a wrong-side self adjuster installed.

BTW; cooked bonded shoes may be trash; the glue may have been compromised. Linings can be de-glazed and if normal underneath,reused. If dragging a small screwdriver over them with modest pressure lifts flakes or digs a rut, then they are toast.
 
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You know the story: Everything is new, but not everything is necessarily good... Since they're drums,and I'm assuming everything bled out fine- (would SORT OF rule out rubber line collapse) I would make DARN sure you've got them adjusted out as far as necessary, because if the pistons have to travel too far out in the brake cylinders, they can actually **** and jam at the end of the bore, locking the brake. Now that I think of it, make sure your self-adjusters are on their correct sides! If not, they could actually change as you drive, causing gradual loss of braking, and then the piston hanging up...
Or a wrong (RHT/LHT) adjuster on the wrong side.
Since I just went thru this...I’ll chime in again. I bled my brakes before discovering that I had a collapsed brake line. The brake system has sufficient pressure to force liquid thru the blocked line but very little pressure to allow the brake cylinders to “relax”. Given plenty of time... the fluid might flow back and release the brakes. Not necessarily what’s happening to you..but that’s what was happening to me.
 
It’s a silicone brake fluid. The main advantage is that it won’t damage your paint. The spray I had wiped right off. However, it may have leaked out easier under heat and pressure. Also, it makes for a softer brake pedal. I may go back to DOT 3.
 
2A721DFE-B1AA-4103-B238-FFF80BE312AE.jpeg

It’s a silicone brake fluid. The main advantage is that it won’t damage your paint. The spray I had wiped right off. However, it may have leaked out easier under heat and pressure. Also, it makes for a softer brake pedal. I may go back to DOT 3.
Note in the photo that the cable is disconnected from the brake adjuster. I guess that prevented the brakes from releasing.
 
I use DOT 5 silicone brake fluid in everything I have. No problems, ever. Even after decades of use and neglect. Not sure that was the cause of your problem. That cable is for the self adjustment of the brakes. The apply and release of the brakes is all in the wheel cylinder.
 
That's messed up.
the strut and it's associated spring are missing
the shoes appear to both be the same length
the adjuster seems to have way more thread visible than should be

without the strut, there is no way for the self-adjuster to work; and the disco'd cable ensures it.EDIT;see below
In your case now, if the shoes stayed out, it's all about the fluid not returning to the master, And there are just a few ways for that to happen. In order of likelyhood;
1) non-functioning Compensating port (easiest to check)
2) faulty wc, or shoes not returning to the anchor pin.
3) faulty flex hose
4) debris in the system
5) faulty distribution valve

BTW; the adjusters are usually marked L, and R; if you put them on the wrong side,IDK I've never done it, but it seems to me that they would adjust when moving forward, instead of only in reverse. Also, the cable goes on the trailing shoe

Silicon fluid is fine, leave it in there, it has nothing to do with your problem. I'm with 66fs, install it and forget it, and forget what the naysayers propone; mine's been in there for going on 20 years, and in the KH 4 piston calipers, which were known they say, to be troublesome. bs.

Edit: this is wrong, the strut is for the parking brake, and does not need to be there.
 
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That's messed up.
the strut and it's associated spring are missing
the shoes appear to both be the same length
the adjuster seems to have way more thread visible than should be

without the strut, there is no way for the self-adjuster to work; and the disco'd cable ensures it.EDIT;see below

In your case now, if the shoes stayed out, it's all about the fluid not returning to the master, And there are just a few ways for that to happen. In order of likelyhood;
1) non-functioning Compensating port (easiest to check)
2) faulty wc, or shoes not returning to the anchor pin.
3) faulty flex hose
4) debris in the system
5) faulty distribution valve

BTW; the adjusters are usually marked L, and R; if you put them on the wrong side,IDK I've never done it, but it seems to me that they would adjust when moving forward, instead of only in reverse. Also, the cable goes on the trailing shoe

Silicon fluid is fine, leave it in there, it has nothing to do with your problem. I'm with 66fs, install it and forget it, and forget what the naysayers propone; mine's been in there for going on 20 years, and in the KH 4 piston calipers, which were known they say, to be troublesome. bs.

Edit: this is wrong, the strut is for the parking brake, and does not need to be there.
The problem is with the right front brake system. According to a photo in my Barracda repair book, the arrangement is correct. The shoes do measure up to be the same size. Is this a problem I have to correct. The points in AJ's post, 1, 2, and 5 I would like some explanation on where to find them. I will stick with the silicone fluid. ( silicon is sand). I don't see where the fluid came from. The hose is new and looks to be intact. The wheel cylinder looks dry. Fluid drops went all the way to my firewall, fender liner, and hood bottom. All in the engine compartment. Hmmm?
Thanks for your insights, I need a little more help on what to do.
 
Ok then;
firstly, the driver's side is the left side
Brake fluid on the underside of the hood can only come from something in the engine compartment. If you have applied and released the brake with the M/C cover off,as you would do during the bleeding procedure, the returning fluid can easily gush thru the Compensating ports, and squirt up to the underside of the hood, even with the hood open.And then it drips down all over everything. Such a high fountain usually only occurs if the brakes were not yet properly adjusted.... or if there is air in the system. After you have stroked the pedal to make it hard, air in the system can be compressed to 800 or more psi. It has become a high pressure air-spring. Then when you lift off she unloads and forces all the fluid you just pumped down the line,back up into the M/C, with predictable results. Once the shoes are adjusted and the air is purged, very little fluid movement is required, and the returning fluid usually only roils in the bottom, with perhaps a lil fountain.

The photo appears to be of the passenger (right) side, and looks to be correct except the shoes should have two different length linings on them; a long and a short; the difference being about 2 inches; and the long one goes on the rear side or to the left when looking at that passenger side system.
Your self-adjuster cable appears to be a lil short. After it is installed, the blade should be resting on the star wheel, ready to crank it down, which should lengthen the adjuster. This event should only happen when backing up, as the entire shoe assembly is cranked around by the dragging drum. Since the cable is anchored at the top,the blade is forced to flick the starwheel. If the shoes are already properly adjusted,then there is insufficient cranking of the assembly to make an adjustment.

The pistons in the wc,have to retract after every application, to allow the linings to properly rest fully against that top anchorpin, so they cannot drag on the drum. If the fluid is not returning to the M/C, for whatever reason, then the linings may not retract far enough to not drag.
If, simultaneously, there was to be an air pocket trapped in the wc, the dragging shoes could, I suppose, heat that pocket enough to expand the air to act like an air-spring, and keep the shoes applied, maybe even increase the drag, in a vicious cycle.
If there was water in there, it would be even worse.
Silicon fluid is not hydroscopic, so any water in there will settle to the lowest point..... which is the wc.
Brakefluid should always be used from a sealed container.
I don't think any of these is your problem; just suggesting the possibility.

Next; as to points #1 and 2
You have to prove that the piston inside the M/C is properly parking, to the rear, so that the fluid can return. From the previous discussion, I think your C-ports are fine, but here is the procedure to prove it;
There are two ways to do this; directly and indirectly.
Since the drum is off, you can try the indirect method.
Make sure the reservoir cap is installed and clamped shut.
Make sure only one drum is off.
Have a helper step on the brake pedal, while you observe the shoes moving out. Ask your helper to stop about half-way down, and then lift off. Those two upper springs in the assembly; (OK WAIT! I don't see the lower spring in there. There should be a spring just above the star adjuster, holding the two shoes together. I assumed it was in the shadows, but I just can't see it; So make sure it's in there), should immediately start to smoothly retract the shoes, back onto the anchor. This proves the fluid is returning,and that the wc's are not sticking . Repeat several times. This also proves any valving in the system,or the distribution block, are also passing fluid... so yur done testing. This would indicate that hydraulically, the system is functioning properly. This does NOT prove the hoses are 100% as at this time, there is no pressure in the system with the one drum off.

As to mechanicals;
Make sure each side has a long and a short lining on it. and that the short one faces the front of the car on both sides. Drum brakes are self-energizing, and the rear shoe does most of the work, so needs to be longer. Well actually, the cheapazz manufactures can save some coin by making the fronts shorter,lol. If you don't have shorts, then as long as all 4 front linings are about the same length then it will be fine.
Make sure your wheel bearing endplay is properly adjusted. If it's loose, the the chassis will move down from it's normal attitude and could force the shoes into contact with the drum. I know it's only a couple of thou when properly adjusted, and then it's no big deal. IIRC endplay is maybe max .007. With drums I run them fairly close to zero.
Make sure the pads on the backing plates where the metal shoes rest are smooth, so the shoes slide smoothly over them. You can put a tiny dab of hi-temp grease on those flat pads to reduce wear. If the pads have ruts/ridges in/on them, grind the high part off. If deep, you can build it up.
Make sure the metal part of the shoes do not rub on the drum, or the step that often wears into the corner down in the bottom of the drum..
Make sure, on a dual-reservoir M/C that it is correctly plumbed. the front-most reservoir on the factory system should go to the rear wheels.
The first inch or less of pedal travel, can be non-functional, as the piston in the M/C is moving out and closing the compensating ports; this is normal.Make sure the pedal returns to the top of it's stroke by itself and rests on the stopper. If you flick your foot off the pedal in the first inch of it's travel, the pedal should sorta snap back to it's parked position and make a satisfying lil thud.

And above all, make sure you have a hard pedal, and that it gets hard in the first 50% or so of it's travel, and that it remains hard with modest pressure for at least 20 seconds, and that it never suddenly drops down.


IDK, that should cover it.
Happy Hunting
 
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Note in the photo that the cable is disconnected from the brake adjuster. I guess that prevented the brakes from releasing.
It appears that the two top springs are identical. Is that normal for your car? My Duster’s primary shoes (and pictures I’ve seen in repair manuals) have a spring that is shorter and larger in diameter than the spring on the secondary shoe.
 
I beleve the two springs are identical because the shoes are identical. I ordered all stock pads and hardware so I think they're correct.
 
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