Brakes: Brakes almost completely locked

[jab-ph]

I got my '58 PH out of a 4 year hibernation and managed to drive it about 5 miles before I gave up and called for a tow. All 4 brakes were locking up upon application and not releasing. Backing the car up seemed to mitigate the issue somewhat but after the next stop they would remain in their near locked state. The brake lights would stay on and then after time would go off. Tried bleeding slightly at the booster but that did not relieve the problem. I recall and it appears to be the case that there was a new master cylinder fitted when I bought the car in '08. The fluid looks relatively clear but I suspect the problem is with the m/c. I rule out the wheel cylinders because of all 4 wheels behaving similarly. Am I on the right track?

[showbizkid]

I am no brake expert, but my first guess would be that the brake hoses have gotten soft during their extended storage and are collapsing upon release of the pedal, trapping the brake fluid in the wheel cylinders.

I would begin by having someone stand on the brake pedal while you watch the hoses and seeing if they balloon upon application, or collapse on release.

[SN-60]

To: jab-ph,------ What showbizkid said. I had the same problem on the right front wheel of a '60 Hawk, and it indeed turned out to be a softened brake flex hose leading to that drum. The hose looked OK on the outside, but
when I cut it open, the inside fluid channel was almost completely collapsed.

[PlainBrownR2]

There's something else that needs to be considered, and I had this happen on the '55, after I completely went through the braking system(it's a single master cylinder) when I replaced the under the floor master cylinder a couple months ago, replaced all of the hard and soft lines, honed the wheel cylinders, bled the system, and first put the car into gear. Up until the point where I put the car into gear, the braking never changed, it did what a typical brake pedal did, a little resistance until it got close to the floor and got hard. But, when I had to unstick the clutch, and put the car into gear on the jacks and spun the wheels, the pedal progressively became harder until it wouldn't go to the floor at all. Something had changed, so I opened the brake reservoir cap, went to both rear wheels, and cracked open the bleeder screws. The bleeders spat out a little pressurized brake fluid, before the brakes released to their normal state. I only needed just enough to get the wheel cylinders to release, which they did, but after I found this out at the rear wheels, I took my one man brake bleeder jar to the front and rear wheel cylinders, and pumped pedal a couple of times. There was quite a bit of air that seemed to have been released from the lines into the wheel cylinders, so I worked the pedal a few more times with the bleeder jar, at the front and the back, until the wheel cylinders could retract on their own. What had happened was the air in the lines, which is a shared system, and wheel cylinders were causing the brakes fully lock up and not release, which resulted in a very hard pedal. After I did that, I didn't have anymore problems with a hard pedal.

[Andy R.]

Could a bit of debris lodged in the tiny M/C compensating port making it harder for the piston to retract?

It might not cause the problem itself, but coupled with old fluid that may have absorbed some water (lower boiling point) might eventually lead to such a symptom.

[tbirdtbird]

Try loosening the adjustment on the rod from the pedal to the M/C (shortening the rod a little) to be sure the tiny M/C compensating port gets uncovered on pedal retraction

[BobGlasscock]

what tbird said. That is what caused mine to lock up.

[SN-60]

To: jab-ph,---- Did You drive Your Packard and did the brakes seem normal in '08? If they did work OK then, I wonder what would have caused the master cylinder pushrod to now be out of adjustment? Did You loosen it?

[BobGlasscock]

After reading SN-60's post above, I went back to your original post to review the 'new' part of your post. In the second reading, the brake light statement confirms to me that your problem is that the mc is maintaining pressure to keep the light switch activated. Loosen your adjustment rod.

[52 Ragtop]

Check the adjustment between the M/C & linkage. They need to be right. If you need new hose's, I can make up fresh ones that are DOT approved.

Jim

[warrlaw1]

What tbird said is exactly what happened to mine. Back off the adjustment at the MC and save yourself a season of grief.