1967 Brake issues

[Timothy B.]

Re: 1967 Brake issues

Michael,

Probably has something to do with the liquid fluid compressing the air and it has no where to go because it can't escape the caliper so it expands when the pedal is released and holds the piston.

[Michael W.]

Re: 1967 Brake issues

Michael,

Probably has something to do with the liquid fluid compressing the air and it has no where to go because it can't escape the caliper so it expands when the pedal is released and holds the piston.

The air will expand back to atmospheric pressure when the brake pedal is released. It does not 'hold' the piston any more than fluid would. Air in calipers does not cause the brakes to lock up- on the contrary.

[Timothy B.]

Re: 1967 Brake issues

Michael,

I have a little GMC Sonoma truck that broke the bleeder trying to loosen and bleed after installing new brake hoses. While waiting for the new caliper to be delivered I pumped the brake pedal and the wheel in question would not release until I loosened the line to let the fluid pressure escape. Naturally after installing the new caliper and gravity bleeding all was fine so I know air in that line had something to do with the fact the piston held the wheel.

That was my experience, believe it or not the brake pedal actually pumped up after a few pumps.

To the O/P I would look for a air entry point if it's just one wheel still locking up.

[Michael W.]

Re: 1967 Brake issues

Not to argue or hijack the post any further, but when the brake pedal is released the relief port(s) in the master cylinder allow all pressure (air or hydraulic) to escape. No idea what secondary problem your pickup had, but it wasn't air in the caliper that caused it to lock up.

We need more info from the OP to go any further.

[Timothy B.]

Re: 1967 Brake issues

Michael,

I understand exactly what you are saying and I agree with you. I just thought the experience with this truck may help the O/P's wheel lock problem. Maybe the brake caliper had fluid and air was in the new hose and got compressed when I pumped the pedal then expanded when releasing and held the wheel. After time it may have escaped and the wheel unlock, that exactly the same problem the O/P described.

I had no secondary problem, after installing the new brake caliper and loosening the bleeder to purge the air from this line all was fine and no more lock up.