My 46 Babe

[My 46 Babe]

Problem with front brakes on my 46 - 1/2 ton pickup.  I adjust the brake shoes manually by turning the two nuts behind the brake plate.  I make sure the brake shoes

have sufficient gap to allow the wheels to spin.  I take off and drive downtown and by the time I get back the brake shoes are locking.  I noticed that initially my brake 

pedal had about two inches of gap before the brakes interact.  Braking seems good, not spongy.  But when I get back from a drive the pedal now has no gap space

and is locked up at the top of the pedal arc.  Like some type of residual pressure is built up and locks my front brake shoes.  I'm puzzled.  Any ideas?

[knuckleharley]

Have you ever tried to immediately open the bleed screw after stopping?

 

If you have,and the pedal goes back down to the normal position,you need a new master cylinder.

 

Sounds to me like you may have a burr or some trash on the piston in your master cylinder,and that is causing it to stick.

[Jerry Roberts]

Residual pressure can be caused by a flex hose coming apart on the inside , out of sight .  Are both fronts locking up ? It would be unusual for both hoses to go bad at once though . Another cause would be a clogged master cylinder port , there is one larger port and also a very tiny one . 

[BobT-47P15]

At one time several years ago, the rear brakes on my P15 locked up when I applied much pressure with the pedal.

I would have to open a rear bleeder briefly to release them.  Cause - as I finally found out - was the inside lining

of that little short rear brake hose was collapsing and blocking return of the fluid to the master cyl.  So...you might

consider replacing the front hoses if you have not already done so. 

[Merle Coggins]

You could also have a plugged relief/vent port in your master cylinder. When things heat up it may be building up pressure within the master cylinder if the piston chamber isn't able to vent back into the reservoir. This may account for your loss of free play. You may also have your brake pedal adjustment too tight which is not allowing the piston to return fully to uncover the vent port. This would give a similar symptom.