Dear Ray,
We have 1957 Thunderbird, 122,000 original miles, engine rebuilt at 90,000 miles about twenty years ago. Recently, the brakes did not feel right. The mechanic, who owns a couple of vintage cars, had a difficult time. he adjusted, bled, and whatever else is required. we finally had the power booster rebuilt. The car stops better but when you let up on the brakes, it does not regain speed until you step on the gas again. Not unsafe but not right.
He feels that it is the vacuum. Right now, the vacuum line in not connected to the booster and a bolt is inserted in the vacuum hose.
Not a good idea to post your contact info on a public forum. I have notified the moderator to remove it.
I don’t know what you mean by “don’t feel right” Please explain more fully.
Yeah, we need more about this, too. Car’s don’t regain speed until you hit the gas. that’s how this works. Do you think the brakes are dragging? Or maybe just one is dragging?
Leave the booster un-hooked. Take a short drive and lock the brakes completely from about 30 mph in a safe area. Get out and look… do you have 4 distinct tire skids? Are they all about the same darkness? Did the car stay straight? Did the fronts lock first? If you can say YES to all 3 questions, concentrate on the master cylinder and booster. If NO, you have a basic problem with the brakes that your current mechanic did not fix. Find a better mechanic.
Hook the vacuum back up. Drive around an vacant area a bit without touching the brakes, or at least as little as possible. Stop and touch each wheel. Are they all warm or hot to the touch? That’s probably a bad master cylinder. If you replace it, get a dual master and have the rear lines broken out. It is much safer. Retest. If the brakes still drag, rebuild the booster again, it was not done correctly before. If one wheel is hotter than the other, the brakes are not adjusted correctly, find a better mechanic.
I have not driven any motor vehicle on a level surface that accelerated when I released the brakes until I pressed the accelerator pedal. I have no idea what OP’s problem is.
Are you thinking the brakes are binding? You can tell by driving a bit, then CAREFULLY touching the wheels to see if any are hot. You’ll need the hubcaps off when you do this.
Your mechanic needs to remove the drums first and inspect the springs. At the age of this vehicle, the springs probably need to be replaced anyway.
The plate that everything is mounted to is called the backing plate. Each brake shoe contacts the backing plate on three pads, one at the center of each pad and one at each end. By shoe, I mean the edge of the metal shoe, not the friction material. I suspect that the grease on these pads had gotten hard and full of brake dust. He will need to remove the shoes, or at least pry them away from the backing plate, clean the pads and put a dab of GP grease on each pad.
I concur with the comments above about removing the drums for a look-see. Beyond that, a couple of ideas
flexible brakes hose somewhere is damaged & collapsing. this creates a one-way-valve effect, so you press on the brake pedal, the brakes apply but when you release the brake pedal the brakes continue to be applied.
the replacement power brake booster may also be faulty. your shop should check to make sure it holds vacuum.
I own a 45+ year old Ford, drums all 4, and there’s a dozen things or more that could fail and cause similar symptoms. Figuring out the cause just requires going through the possibilities one at a time.
btw, make sure the bolt in the large booster vacuum hose isn’t so small that it could be sucked into the engine’s intake manifold on high levels of vacuum. that would make your brake problems pale in comparison.