Front Drum Brake Rebuild: Won't Bleed

[wilos]

MY 69 C10 was pulling to the right when braking. The truck is mainly original front drum without power steering. I took the drums apart and found that the drivers front wheel cylinder was leaking. I ordered all new front wheel cylinders and front shoes and rebuilt the brakes.

After getting everything back together I went to bleed the brakes. Since I didn't drain the whole system or touch the backs, I started by only bleeding the fronts. I couldn't get much pedal when bleeding the fronts and the fluid is only slowly coming out of the bleeders on both left and right sides.

Because of this, I tried to bleed the back brakes. When doing this the pedal came back to about half of its normal stiffness. Went to do the fronts again and the pedal went completely away again.

I did adjust the star wheel on the fronts so that the shoes were just rubbing on the drum.

Could it be my master cylinder? If so, would I still get some pedal when doing the rear? Is there something that I am just missing?

Thanks in advance

[BLT gmc]

?Bad rubber/flexible brake hoses? Good luck, Bruce

[wilos]

If it was a bad flexible line, wouldn't only one of the two sides be affected? Right now both left and right are exactly the same issue. The trucks was still stopping prior to redoing the brakes, so I don't think it is the hard lines. How do you tell if a master cylinder is bad?

[BLT gmc]

power or manual brakes? Dual or single chamber master cylinder? Would be very unusual to have both flexible lines fail at the same, but when handling them in a wheel cylinder change weird stuff can happen inside them hoses. To check the master cylinder you will need to disconnect the steel line at the master cylinder to the front brakes. I would the fashion a scap piece of steel line from that opening the frt brakes were hooked to. Bend the scrap line to empty back into the resovoir. Pump the brakes to see if there is fluid and pressure coming from the master cylinder.

[wilos]

Manual brakes with a dual chamber. When I get home tonight I'll check the master cylinder. Thanks

[wilos]

It appears to be the master cylinder. When the front line is disconnected and the brake is applied, only a small amount of fluid is discharged. I checked the rear line and when the brake is applied a far larger quantity is discharged. I ordered a new master cylinder and will report back if this indeed solves the issue.