air in brake lines

[dmjlambert]

Hi folks. My truck is a 69 CST/10 with manual drum brakes. The brakes have been working just fine since I had a friend help me with getting them going. As of that time about 2 years ago we put new cylinders on each wheel, new master cylinder, new shoes, new spring kit, and determined the drums looked fine so we reused those. The brake lines and hoses are in good condition and the system has no leaks. I have neglected to check the fluid level in the brakes, and I let it get low. I noticed the brake on first press when coming to a stop felt different, it was traveling closer to the floor. So I checked and topped off the fluid, but I believe I let it get too low and put some air in the system.

The brakes stop the truck fine, but I am concerned about the feel and about the pedal travel. When I am driving up to a stop sign, if I press the brakes, they go down too far, I think it is about and inch from the floor, and the truck stops OK. I can just tell there is a different feel to it. If I go again and stop some time later, and press the brake pedal, it goes to within an inch of the floor, and if I lift up my foot while coming up to the stop sign and press the brake pedal again, it goes down about an inch higher and feels more like the normal braking position. After coming to a stop, if I maintain pressure on the pedal, it does not sink any further towards the floor.

I am thinking these conditions point to air in the brake lines. I bled the heck out of the system. I used a one-man bleeder, which is a little bottle held with a magnet to something higher than the bleed port, and I pumped the brakes and emptied the bottle multiple times and kept filling the master cylinder with fresh new fluid. I don't think it is likely I would have left any air in the system, I think I know what I'm doing, but it still behaves the same way, so maybe I am missing something. The driver side rear is the longest running line so I started there, and then did passenger rear, then passenger front, then driver front. I have pumped the brakes enough to fill the little bleeder tool bottle several times after seeing the last bubbles go through the tubing, just for safe measure.

Each time I had it bled i took it for a test drive and found the same conditions. I repeated the bleeding a couple times on the 4 wheels, and ended up using about a quart of O'Reilly Dot 3 fluid, which is the same stuff we used when we filled the system the first time.

Do you guys think it is still likely I have air in the system? I am thinking the symptom says so.

I'm going to end up re-doing the system with new braided hose to replace the old hoses, and new drums, shoes, etc. because at the time my friend was helping me he knew more than me and we did not turn the drums, and put the long shoes in the wrong positions, and probably other minor errors, so I want to re-do it because the thought of some of the stuff I have since learned we should have done more correctly is bothering me. I may just replace the master cylinder again if I can't figure out what is up with my failure to properly bleed. And I'm going to put a reminder in my phone to check the darned fluid level and not neglect this thing again. I estimate I have 8000 miles over the last couple of years since getting it going, but it is a guess since my odometer doesn't work.