Calipers are centered with included washers. Before I replace the new master cylinder I'm going to rule out it having a residual valve in the disc side line port. I'm told I can verify with a small wire inserted in the port. If it stops short, it has a valve. Should go in further without. It's a #101378 Cardone unit.
Cardone has been screwing up a lot lately Personally I’ve had 7 out of the last 12 cardone items be bad, malfunctioning, or inoperative. My parts guys have been going nuts and say it’s not just me
Back when I worked at an auto parts store, Cardone did not have the best reputation for their "rebuilt" parts. I would suspect the m/c.
I would suspect The MC. Cardone sucked up to 94 when I worked in auto parts store wouldn't expect better now. I'd only use : an OE master ,Wilwood, Baer, or SSBC. brakes probably aren't the place to save a few bucks.
I had the same problem on my 37 Ford with Wilwood front calipers and Ford rear drum brakes. The fix was the remove the top bolt holding the calipers and moving the caliper until the bleeder screw was vertical. Then bleed the front brakes, that fixed my problem. The caliper bleed screw wasn’t vertical and it was trapping air, which then compressed and locked my front brakes. Sent from my iPad using H.A.M.B.
I'm bleeding the system with a motorized vacuum pump. Removed the brake hoses today and blew air throughout the system again to verify clear lines and hoses. Checked the master cylinder for residual valve , none found and bled the system. Locked up tight after the pedal was pressed. I removed the caliper bolts to allow the caliper to float and it stayed locked. Gonna replace the master cylinder Monday.
Before you toss that one, loosen the 2 or 4 nuts holding the master to the firewall at least a 1/4 " and see if that makes any difference. That will at least double check the pushrod clearance just in case it's not as free as you think it is. Ralphie
It's an under floor frame mount. Already did that. I understand that's the first thing that comes to mind when brakes have this problem but I've tried to make certain pushrod clearance is not part of the issue. Thanks Ralphie! I am sitting here second guessing whether I should try bleeding by hand before switching out the master just to verify I'm not preloading the system using vacuum. Shouldn't but I'm clutching at straws now.
Even if you are using a vacuum bleeder, could the not-vertical bleeder screws still be trapping air like Viper's problem? Can you see down into the top of the master and look into the hole in the bottom of the cavity, and see if the plunger is returning all the way to allow the fluid back up?
With the brakes locked,,, When you open the bleeder ,,, Exactly what happens? After you open the bleeder ,,, What happens if you try the brake pedal again? Do they lock again?
If I open any of the eight bleeder screws on the calipers fluid sprays out under pressure and the rotors turn with one finger. If I depress the pedal the calipers compress and stay locked until pressure is relieved thru anywhere in the front system. The cylinder piston returns to it's original position. Determined by checking pushrod depth.
Then I’d say all of your second guessing is just taking up space in your brain without paying any rent.
Late to the party here. Same experience with Crap-Done rebuilt parts. When I installed a Wilwood master cylinder in my old Volvo (same general configuration, master cylinder below the floor level, manual push rod (not power), disc brake conversion on the front), the Wilwood instructions instructed me to remove the check valve from behind the disc brake output port for this configuration (external 2 PSI check valve on the front, adjustable proportioning valve on the rear).
Once the pedal is pushed and the brakes lock, loosen the front brake line at the master and see if the brakes release. If they do, the only thing it can be is the master or the master related parts, which you have already cleared as not being the problem. If the brakes don't release, you need to move to the next thing down line from the master, in the front brake system and loosen a line on the caliper side of whatever that item is. If the brakes release, replace that item, if the brakes don't release, move to the next item on the front brake system. At some point something will release the front brakes. The last thing you opened that caused the brakes to release is the problem. This is the only for sure way to find what is locking the brakes. Once the problem child is found, a repeat of the process (you can skip to the suspected problem part) should show the same result. I have rarely seen where a problem associated with a master cylinder for a front brake problem was actually caused by a rear brake problem. It may sound dumb, but are the rear brakes locking up as well? Gene
Some of the Mustang-type master cylinders had internal residual pressure valves. They are rubber and they are just inside the port where the brake line attaches. Take the brake line loose at the port and use a small wire or drill bit to be certain there is no rubber valve inside. You'll feel it as soon as you gently push the wire into the port. If there's one in there you can use small needle nose pliers to pull it out. Then use your choice of appropriate aftermarket in-line residual valves to finish your system. Good luck.
You have changed everything except the master cylinder - change that from another manufacturer Sent from my iPhone using H.A.M.B.
Most drum/drum and disc/drum dual masters had internal residuals up to the mid '70s. You're correct about checking for a residual, but the drum port tube seat(s) should be pulled to properly remove the residual. This can easily done with an "easy-out" extractor.
Ok, so I ordered a Corvette style master cylinder Monday and it won't fit. Flange is too wide and there is limited room due to the round tube center crossmember assy on the aftermarket frame. So I removed, disassembled the existing cylinder, cleaned everything and reassembled it. I hand bled the brakes after reinstalling the cylinder and the brakes release. Not freewheeling but I can turn them by hand. Gonna drive it a short distance tomorrow and see if it feels right and doesn't overheat. Still didn't find anything obvious.
Drove it and all was well. Took a few miles to seat the pads and the pedal felt good. Found a leak in the LF braided hose so I replaced both hoses, rebled it (vacuum) and the brakes were locked again. Thought back to what I had done to correct it and the only difference was I had hand bled the system after the master cylinder R&I. That did it. Rotors freewheel now. It likes manual brake bleeding. Thanks for all of the advise. I was running out of hair to pull out .
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