The air noise I'm hearing at the pedal slightly worries me, but if it was leaking, I would think it would be a hard pedal rather than a soft pedal.

 

Your booster is doing it's job. The air rushing noise is pretty normal on a pedal with excessive travel.

If you pump up the brakes, does pedal height improve?

If you stand on the pedal, will it slowly sink to the floor?

 

The pedal height does not change when it is pumped up, and if I stand on it it doesn't drop. I don't see any leaks anywhere. It seems like it still has air in the system, but I am not getting any air out when bleeding them any more.

 

Think you need a helper for your bleeding... Or, a pressure bleeder. Good possibility that just pumping the pedal with the valves open just makes the air move back and forth, not out. There are also 'one man bleeder valves' available. Basically a one-way valve built into a bleeder valve.

 

+1 - That's why I was questioning your bleeding process. Even with a hose going into a jar of brake fluid from the bleeder fitting, sometimes air can travel around the bleeder valve threads.

Another option (if you have time) is to let gravity do your bleeding. Make sure your master cylinder is full and the truck is sitting on level ground, then crack the bleeder valve at the passenger side rear wheel. Once you see brake fluid dripping at a decent clip, close the valve, fill the master cylinder and go to the next wheel and repeat until you have them all.

 

I agree with Atomic Dog, gravity bleeding is always my preferred method of bleeding. Gravity bleeding does not always work depending on proportioning valves and ABS units. You should still bench bleed the master cylinder. Gravity bleed keeps the brake fluid from foaming up from air bulbs. Gravity bleeding really works well on completely empty systems, just need to be patient. Also be careful when bleeding drum brakes, sometimes fluid will leak between wheel cylinder and backing plate and soak the brake shoes.

 

Last thing - hopefully you don't have a slow leak in a brake line. Be sure to check the rear metal brake line - it is notorious for leaking, especially around the rear of the fuel tank area. I changed all of my metal mild steel brake lines not too long ago, as metal brake lines on a 15+ year old 3/4 ton truck tend to rust over time and fail at the most in-opportune time.

 

Did you get this issue fixed yet?