Brakes Sticking on

[XBRIT]

Hi Guys, well we are back at home in Monroe WA after a year in Montreal. My 72 Challenger (with power brakes) has been in storage and now I am working thru. the smaller issues to get it as near perfect as I can. My problem is after the rebuild I changed every thing on the braking system including, proportional valve, master cylinder, front calipers and rear slave cylinders. My issue being that when I brake the car brakes seem Okay but the brakes remain on until I push the brake pedal again it then release the vehicle as the brakes seem to lock on. The only part I did not replace is the brake booster as the unit seemed to hold a vacuum. Any input from the forum would be appreciated.
Cheers,
Mike

[Chryco Psycho]

the pushrod out of the booster may be slightly too long & not allowing the piston back all the way inside the master cylinder , it is a 2 piece unit & can be threaded back in to shorten the rod

[burdar]

My guess is that it's a prop valve issue.  Who did you buy the prop valve from?  The valve that Inline Tube sells is defective.  If you still have your old valve, swap it out.  It would be a good idea to double check the pushrod length while you're there.

[XBRIT]

Thanks guys, I did not think that the push was adjustable?? & the prop. valve was so rusty I junked it. It there any test that I can perform to check either of these?
Cheers

[burdar]

My original prop valve was very rusty too but it worked just fine.  I soaked it in EvapoRust and it came out looking new.  The EvapoRust isn't an acid and only attacks the rust.

To check the pushrod, take the master cylinder off of the booster.  Measure how far the pushrod is sticking out past the mounting face of the booster.  Then measure from inside the master cylinder piston to the mounting face of the master.  I adjusted my pushrod so that I had the same measurement in both places.  I used a gasket between the master and the booster.  That gave me about a 1/16" clearance between the end of the pushrod and the master cylinder piston.

[XBRIT]

Can you pull the Master Cyl. from the Brake Booster without bleading the brakes?

[dodj]

Can you pull the Master Cyl. from the Brake Booster without bleading the brakes?

Yes