power booster question

[frankyjoet]

I changed the rear brakes to disc, i now have 4 disc wheels. my 73 gmc truck brakes need to be bled. When i tried to bleed them i hear an air noise from the power booster rod. now since i replaced all brake rotors and calipers, i assume or think that there is air in the brake lines. the first set you do is the rear, then alternate between the front, is this correct? i read from a good source that if the brake pedal is HARD, then the booster is bad. Also a little noise is normal. My ? is the booster ok? If so i can bleed alll the brakes. Thanks for any help.

[Duster]

Is the truck running when it makes the noise?

When I bleed brakes, I do the old timer "gravity bleed" method of opening the master, and cracking all the bleeds open with mason jars and surgical tubing to catch the run off. It works like a charm, and insures you have all new fluid through your lines with out air. It takes a couple hours to do though. You just keep feeding the master untill clean fluid starts coming out of all calipers. Then tighten them down and you have airless lines.