Brakes: Hydro-vac on 62 GT Hawk

[Jim Finley Sr]

I replaced the MC and now brakes are not releasing with engine running and sitting still. Brake lights stay on for about a minute until brakes release. My mechanic thinks it's a bad Hydro-vac and is happily ready to replace it. This newbie needs advice before I send four hundred bucks north. Thanks in advance for your input. Jim in Atlanta

[PackardV8]

Could your replacement master cylinder have had a check valve in it?

jack vines

[Jim Finley Sr]

Could your replacement master cylinder have had a check valve in it?

jack vines

Hmm... Good question Jack that I will have to pass on to the mechanic. Actually only drove the car a couple of times after purchase before putting it in the shop for the master cylinder replacement And on those occasions it seemed that the brakes weren't releasing immediately when I made a stop.

[Dwain G.]

First thing to check is adjustment of the push rod between pedal and master cylinder.

[Jim Finley Sr]

Thanks Dwain; for sure before I order a new Hydro-vac

[Jim Finley Sr]

Dwain, can you comment specifically on how to adjust the pushrod? Thanks

[Dwain G.]

Adjust the pushrod underneath the car so that it completely releases the piston inside the master cylinder. The pedal
inside the car should move 1/4" to 3/8" before the pushrod contacts the piston inside the master cylinder. Don't confuse this with pedal travel. You should be able to feel the free play by pushing the pedal with only your pinky finger.

[Jim Finley Sr]

Thanks a mil Dwain. Will put the fix on it first thing in the morning

[Studebakercenteroforegon]

The two short flex hoses are notorious for acting like check valves when they get deteriorated and restricted inside. More than once have I sold a pair of these hoses to someone having a similar problem and the report to me was that cured the problem.