Technical I need some brake help please!

Good morning everyone, hope I'm in the right place, it's been a couple of years since I posted here. I just got my 1960 falcon gasser up and going. I'll make a list of brake components used below, I'm fighting some brake issues that may or may not be related. So I'm lucky enough to be able to try the car out on empty, straight rural roads. I lost brakes a couple of times, so I put on a disc/drum master cylinder for a mustang, mounted at the firewall with no proportion valve or residual valve(common swap on the Falcons). The car would still lose them, two or three pumps they're back.
Now we noticed that the front calipers are hanging up and won't release until we manually push the piston back in, or if we crack a bleeder/brake hose. This also happens with the brake rod completely disconnected from the car, if I use a screwdriver to push the master.
Every piece is new, pressure style brake light switch, mustang master cylinder, all new lines, hoses, wheel cylinders and speedway metric gm calipers that came with the straight axle kit. We've bled the brakes a half dozen times or more with no results. Any help would be appreciated.

 

Have I mentioned that brake problems are so common that we need a sub-forum just for brakes?

 

Possibly ‍♂️ I haven't been on here in ages.

 

Sounds like poorly manufactured parts. The calipers should return and the master rod should never fall out.

 

Poskibly a bum master.

 

Yeah they're definitely not returning, the rod never fell out. I just had it out to make sure that it wasn't the rod holding pressure on the master.

 

I do have a lifetime warranty on it, I'll have to swap it out and see what happens.

 

I am looking for the list of parts.
?
I need to see the flex hoses to the calipers, replaced.
If not,, then do that.

 

Sorry must have forgot it.
Brand new speedway braided front hoses
Brand new pressure style brake light switch
Brand new Napa 67 mustang disc /drum master cylinder
All new lines/fittings, fluid etc
Edit: I also for the hell of it, took the lines and put the front to the rear and vise versa, the problem stayed at the front. I'd imagine this rules out the master and has to be in a front line, hose or caliper? This stuff is happening in the garage stationary just tapping the brakes once.

 

Arn't metric calipers problematic in brake swaps?

 

Mine sure are but they came with the axle kit, I do indeed have the recommend 1" bore with the master I'm using as well. Literally all that's holding me back from driving it around are these damn brakes.

 

Has a familiar, reassuring, ring to it! Could be a good tagline?

Chris

 

It seems that your calipers and/or master cylinder aren't flowing properly. It sounds like something's not plumbed right and/or there's a check valve or something in the system that's not needed, or something's missing from the system. It's possible that the caliper pistons are getting mechanically hung up, also, but that doesn't seem likely. Maybe it's all due to a malfunctioning master cylinder. I don't know how, but it seems like you should be able to test the flow and/or pressure produced by the master cylinder.

Is the brake light switch mounted on the master cylinder or in-line? If in-line, does it have an arrow showing the flow direction? They're probably not directional; it's just a thought.

Are the caliper bleed valves at or near the top? As in, are the calipers mounted correctly? I don't know if they'd go on incorrectly, but again, just a thought.

Is the pedal setup allowing the proper actuation/travel of the master cylinder? I think that's (at least partly) why you said you operated the master cylinder by hand.

 

You might try observing the relief port in the master. Apply the brakes, then release your pressure on the pedal. Pop the cover off the master and see if the port is closed by the m/c piston. It may be possible that wrong components were****embled at the factory.

 

Seems after all you've done, problem would point to the master. Master is holding pressure, if you have to crack a line to release the front calipers. Between this issue and having to pump the pedal after loosing pressure...I'd suspect the master is wonky.

Would that make it easier for you to help troubleshoot brake problems?

 

The only way calipers " retract" is by the runout of the rotors bumping them !

 

Cody, if you loosen the front brake line right at the master cyl, do the front brakes immediately release? If so, it's the master cyl. It either has a residual check valve in it that it shouldn't have or the piston isn't uncovering the tiny compensating port. I****ume the piston in the master is returning all the way back against the snap ring.

Terry

 

Got a picture of the master cylinder?

 

I'm at work at the moment, this is exactly the same thing though.

 

I would look in the rear hole for the front brake line and see if there is a residual pressure valve in there by mistake. There should be one in the front port for the rear brakes if drums and shoes.

 

Good afternoon! Thanks for the reply, I have an inline switch that didn't have any markings for flow on it or the tee. The bleeders point up and I do seem to get full travel with or without the rod hooked up

 

You say that cracking a bleeder allows the calipers to retract. That means that something is holding a pretty good pressure in the system. I'd pump them up, release the pedal and crack the line at the master cylinder. If the calipers retract then the problem is in the master cylinder. If they don't, go to the next connection and crack a line. Keep doing this, working your way connection by connection toward the calipers until you find the point where the pressure is being held. That will pinpoint your problem.

 

In the last 18 months, I have had 3 brake hoses make their own gate valve so the front brakes would not retract. First thing I always check when I have non retracting calipers. These hoses were all on different cars.

 

They retract by the distortion in the square shaped seals re-alligning ,not by run out.


Metric low-drag calipers have a bevel/tapered groove machined into the body to allow more deflection [and more retraction]


Run out causes pad "knock-off" which causes a whole new driving technique [The "chicken-shit school of driving"]
Piss-poor disc brake kits are problematic for knock off due to brackets flexing or not being perpendicular to the disc.
Loose wheel bearings also cause pad knock-off. [especially disc brake rear end conversions]

Only with mismatched M/C's!
Metric low-drag calipers should be used with a stepped bore [quick uptake] M/C.

I've used stepped bore M/C successfully without Metric low-drag calipers [the other way round is a nightmare]
A stepped bore M/C is a good way to use a smaller bore M/C for booster delete and not have excess initial pedal travel.
On my old Lotus Cortina I used a 3/4" stepped bore M/C from an 80's Mercedes [and had a nice high pedal]

 

If you swapped front to rear lines on the master and the rears are not locking up .

I would suspect a flex line .

the braided lines , while look fancy . And most kits will use cheap parts leave a lot to be desired .

the flex line is nothing more then a flexible synthetic tube the brake fluid flows through with a protective coating ( usually layers of reinforced rubber ) your case braided fancy stuff .

fairly easy to kink , or squish ( a rotor or caliper being dropped on it to tight a bend trying to ship it in a small box .etc

when you crack the bleeder screw the caliper releases ?

crack the flex line at the calliper , also where the flex line attaches to the hard line and see what happens .

im betting my coffee and dounut you got sub-standard lines in your kit .

 

As stated several times already, when the brakes are locked up, loosen the fitting at the master, if the brakes release, the problem is in the master. Since you have swapped the lines on the master and nothing changed, I wouldn't expect the locked brakes to release when the line at the master has been loosened, but this would eliminate the master from the list of possible problems. If loosening the line at the master doesn't solve the problem, tighten it bak up and move to what evewr in the next thing on the line.
If you loosen every fitting between the master and the caliper and still don't have free brakes the issue is probably the calipers. But skipping anything on that line between the master and the caliper will give you too many possible problems. Test loosen each step along the line until you find the one that releases the brakes. The 1st loose fitting that releases the brakes is attached to the problem part. I have my suspicions, but following them may miss the part that really is bad. Check every item on the brake line until you find the one that releases the pressure.

New parts can no longer be considered good parts. That ship is long gone.

 

If I crack it at the flex & hardline junction everything releases, even up at the master. After some digging today I've discovered they gave me a power brake master. Hopefully this is my issue.

 

A power or non power master I don’t think is a thing other than having a booster attached .

you could possibly have a 4 wheel drum brake master with the valves installed in the lines .

if you take the lines off you will see little brass plugs in the ports

if your careful these can be removed .

 

A non power master will have a deep hole for the pushrod, a power version will have a shallow hole. This deep hole prevents the rod dropping out, which isn't an issue when a booster is present.

No difference otherwise, to the best of my knowledge.

Chris

 

You do have the master plumbed rear reservoir to front brakes?