1971 c- 50 brake help

I am helping get a 1971 chevy c-50 going and it's down to the brakes. The pedal just goes to the floor. I broke one of the front bleeder loose but I don't get any fluid out. I see there is two bleeders do I need to have both open to get flow? One more question, why is there a bleeder on where you would put brake fluid in?

I am helping get a 1971 chevy c-50 going and it's down to the brakes. The pedal just goes to the floor. I broke one of the front bleeder loose but I don't get any fluid out. I see there is two bleeders do I need to have both open to get flow? One more question, why is there a bleeder on where you would put brake fluid in?

If you're talking about the master cylinder, the bleeder is there to remove air from the cylinder. If you run low on fluid, it's common to get air in there and that will cause the brake pedal to collapse.

I had a long reply to this post and lost it, the thing timed out on me.

One step at a time. If the truck has sat around, think about a new master cylinder. If the pedal goes to the floor, the piston travels to the portion of the bore that accumulates crud. This will cause a master failure sooner than later.

I would get a new or rebuild for it, bench bleed it and install it. From there you should be able to bleed the wheel cylinders.

Bob

This truck sat for 9 years!! When I opened the master cylinder cover it had junk on the bottom.
What do you mean by bench bleed it??

This truck sat for 9 years!! When I opened the master cylinder cover it had junk on the bottom.
What do you mean by bench bleed it??

Bench bleeding is the removal of air from the master cylinder, before it is installed in the vehicle. It's a critical step.

Generally, you fill the cylinder with brake fluid on the bench (hence, 'bench bleeding'), then attach a bleed kit to the line connections (generally, most replacement cylinders come with a bleed kit), take the clear tubes from the nipple fittings and stick them in the fluid in the reservoir. Press the plunger in as far as it goes, several times. The goal is to ensure that no air bubbles remain in the fluid.

Leave the kit in place when mounting the cylinder in the vehicle, taking care not to spill any fluid. Once you're ready to attach the brake lines to the cylinder, do that one at a time, only then removing the nipples from the bleed kit. Bleed the rest of the system at each wheel, exercising extreme care not to allow the master cylinder reservoirs to run dry (if this occurs, you will need to bench bleed the cylinder again).

When I was in a shop we would pressure bleed it using an Ammco unit, worked great and it was bled in like 10 seconds.

I've been using this method on the bench for years and it is quick too. I clamp the master in a bench vise, one ear will do. Fill the master, put 2 fingers over the line ports and push the pedal rod in, let it come out by itself. Do this until there are no more air bubbles coming up from the ports in the master reservoirs. Of course this done with the cover off. Remove the fingers, install the master.


If the master was that funky, figure on replacing the wheel cylinders and give the lines and all flexible hoses a close inspection. A C50 is a lot of truck to stop.

Once the master is installed and the system is bled, you can crack the master bleeders and give the pedal one shot for each of them.

Bob

Is this a single master with a Bendix slave/booster under the left running board, or just a plain old (automotive type) master cylinder? I know the 60s and GMC 6500 had the remote booster, but don't know if that applied to 50s.