Hello all, its been a long time since I have been on this site but its good to be here again! Recently Ive been working on a '59 F-100 for a buddy of mine, and I am having such a hard time with the brake system I am almost at my wits end. I thought I would share the insanity with all of you and see what you thought...

It has the original style single reservoir master cylinder. When he first brought the truck over it was empty and looked like it had been that way for a number of years. I removed the MC, cleaned all the old gunky fluid out with clean brake fluid and parts cleaner, and bench bled it. Seemed to get all the air out just fine, I went until I saw no bubbles and my trusty wooden dowel became nearly impossible to push in.

I had a buddy come by to help me bleed the rest of the system. I cracked all the bleeders at each one of the wheel cylinders first to make sure that I wasnt going to snap any off after I called a friend over, of course closing them off again before we got to work.

I started at the right rear, got a few solid pumps of fluid, and then every pump after that had a very large amount of bubbles. We bled the right rear for about 20 pumps of the pedal, I refilled the reservoir before it emptied, and still was getting a LOT of air bubbles. No fluid was leaking from the lines. I just figured this system was a little bit harder to get the air out than most any other brake job Ive done, so we diligently kept on the bleeding process. But after about 40 more pumps, with still massive amounts of air bubbles coming from the back rear I was starting to get frustrated. I checked the fluid level in the MC and realized it was dangerously low, so I figured that we went too far, I had been introducing air back into the system, and that I should just stop while I was ahead and start on a new day.

Well today was the new day. I pulled out the MC again to bench bleed it again, in case I let the fluid level get too low. The dowel hardly moved, and no air bubbles came out so I guess it never went dry like I feared. Reinstalled the MC, started the bleeding process again at the right rear (with a different buddy, not that I was blaming my bad luck on the first guy- I guess the buck stops here right?) and it took probably 5 pumps or so and I got a solid shot of fluid, finally. Thinking bad thoughts about my first buddies capabilities, I moved onto the left rear. I had my partner do about 10 pumps of the pedal with nothing but massive air bubbles coming out of the left rear. Now there is a single line going to the rear that tees at the rear axle, so since I got a solid shot of fluid at the right rear, it should not have taken much to bleed the shorter line going to the left rear.

About this time I started to suspect that the MC actually was bad, and that somehow it was letting air into the system. I figured that since I used a wooden dowel for the bench bleed I was not getting enough of an advantage (even though a wooden dowel has been enough to bench bleed the other 13 or so other master cylinders I have bled in my short lifetime). But just to silence the voices, I left the MC in the truck this time, reinstalled the plug in the line, and had my buddy push down on the pedal very slowly while I looked in the reservoir. No bubbles, and with all his force on the pedal, it would hardly move. Again, verified that the MC was definitely bench bled, and was not introducing air to the system.

Well back to the left rear wheel cylinder. I have gone through over half a gallon of brake fluid, the MC has no trouble moving fluid through the system, but I am still getting massive amounts of air at the left rear. I know some systems like to hold onto air but this is getting absurd. How can there still be air bubbles coming out of the bleeder valve? Since I was just about to run out of brake fluid, and I was getting very frustrated by this point, I closed the valve, had my buddy push down to test the pedal thinking that maybe I was just having a bad dream and that I had magically bled the brakes even though all I could see was air bubbles. The pedal went straight to the floor, no pressure. Of course I opened the left rear bleeder while his foot was still on the floor, saw another squirt of mostly air bubbles, then closed the bleeder before I had him bring the pedal back up (heaven forbid I introduce air into the MC by having him do a test pump to test the pedal pressure)

So there you have it... How is this possible? Where the heck is air getting into the system if there arent any puddles of fluid on the shop floor? After over half a gallon of brake fluid run through the lines and still getting air bubbles I am at a total loss. Sorry to make such a long story out of my tribulations, but I wanted to make sure anyone reading this wasnt thinking 'oh great, another dummy who doesnt know how to bleed brakes' Who knows maybe you are thinking that, and if you are, please, enlighten me! Thanks all