[68FB400]

I have just replaced the brake booster on my 68 Bird as it had a very audible vacuum leak. While I had it off, I figured I'd be safe and replace the master cylinder as well. So bought a new master.

I bled the brakes, starting off on the rt rear, then the left rear. Pressure was building and everything looking good until I got to the rt front. Then, it went down hill. Lost all pedal pressure. Tried the left front and nothing. Thought the master was bad and tried another new one tonight. Same thing happened when I got to the rt front. What's going on here?

A brief history: The car originally had 4 piston caliper disks. 2 years ago, the prop valve leaked and I replaced it with a new repo unit and reman master cylinder. After the 4 pistons kept leaking, last year I converted to single pistons with local part store reman calipers & new lines. They were working ok, but still a little spongy.

What's going on here? Are the front calipers bad? Should I not be using the original prop valve and distribution block when using the single piston calipers vs 4 piston?

Any thoughts/suggestions would be greatly appreciated. My wife's getting tired of all the leg work!

Thanks
Wayne

[68FB400]

I have just replaced the brake booster on my 68 Bird as it had a very audible vacuum leak. While I had it off, I figured I'd be safe and replace the master cylinder as well. So bought a new master.

I bled the brakes, starting off on the rt rear, then the left rear. Pressure was building and everything looking good until I got to the rt front. Then, it went down hill. Lost all pedal pressure. Tried the left front and nothing. Thought the master was bad and tried another new one tonight. Same thing happened when I got to the rt front. What's going on here?

A brief history: The car originally had 4 piston caliper disks. 2 years ago, the prop valve leaked and I replaced it with a new repo unit and reman master cylinder. After the 4 pistons kept leaking, last year I converted to single pistons with local part store reman calipers & new lines. They were working ok, but still a little spongy.

What's going on here? Are the front calipers bad? Should I not be using the original prop valve and distribution block when using the single piston calipers vs 4 piston?

Any thoughts/suggestions would be greatly appreciated. My wife's getting tired of all the leg work!

Thanks
Wayne

[nightwrencher]

after bleeding the rear, or if you start getting spongy, re-bleed the master cylinder in the car. I just plumbed all new lines in my 66 chevy truck a couple months ago and did a disc brake conversion in my 68 fb a couple weeks ago with all new lines/master cylinder. both times for whatever reason:

1. none of that "one-man" vaccum pump crap worked (never did for me) I just use it sometimes to get some fluid in the lines.
2. I had to do id shady-tree, cracked the bleeder, pressed the pedal down and held it down with a 2x4 wedged in the seat
3. after initial attempt, started at the front until got ample fluid, went to rear, and back to front.
4. had to re-bleed master cylinder after got brakes holding pressure
5. re-bleed from rear to front

I don't know why I always have to do it in that similar procedure, but on my disc conversion, I saved a lot of time doing it that way and was stopping in about an hour. on the truck I spent 2 nights bleeding the rear waiting for the fluid to push air free.
if your wife is willing to help it will be even quicker. just start off pressing the pedal down once slowly and stopping at the botom and tighten bleeder. tell her she won't need to pump that much. once everything has decent pressure, do the "pump-and-hold-it" deal.

[68FB400]

I did bench bleed the master before I put it on the car. Not sure how to bleed the master again ON the car. Could you elaborate?

[Scarebird]

I would trot dowm to the parts store and get a pair of lines and fittings to work with your master. Bend them in a 270 degree loop so the open end is submerged in fluid, then pump to you're happy, then reconnect your existing lines.

[68FB400]

I've got the plastic lines that came with the master to bench bleed it. But if I take off the hard lines now and bleed the master on the car then I've opened the lines and allowed more air back in. Defeats the purpose?? Unless you're thinking the master has air and has to bled again before bleeding the lines. I'll give it a shot tonight.

Is it possible for the master to take on air during transition from bench to install on the car? I bench bled the heck out of it.

[68FB400]

Well, after trying the different suggestions again tonight, I still had nothing up front, no pressure.

Out of desperation, I pulled the old, previously rebuilt master and put it back on. Whaddya know, full pressure, firm pedal!!!!

3 nights, 1/2 gallon of brake fluid and a roll of the eyes from the wife later, it should be back on the road. Too late to test drive tonight.

Seems 2 brand new masters from Advanced Auto were both bad. Will have nice talk with them tommorrow.

[Scarebird]

typical nowadays...

[67 455 Bird ragtop]

I use speed bleeders on all my calipers. Makes bleeding a sinch. Even with a new or empty master cylinder. They are cheap and readily available at most parts stores.

[CDJr]

LMAO @ roll of the eyes from wife. If I had a nickel for every time my wifes given me that look, I could buy another Firebird.

[YVEYANT]

THIS MAY SOUND VERY SIMPLE, BUT IT IS A MISTAKE OFTEN MADE. WHEN YOU BLEED YOUR BRAKES ARE YOU KEEPING AN EYE ON YOUR FLUID LEVEL IN THE MASTER CYLINDER? IF THE FLUID LEVEL GOES DOWN TO LOW YOU WILL BE PULLING IN AIR. WHEN THIS HAPPENS YOU LOOSE ALL PRESSURE AND WILL HAVE TO START OVER AGAIN. A GOOD PRACTICE IS TO REFILL YOUR MASTER AFTER EVERY WHEEL BLEED. ANTHONY

[68FB400]

I never let the fluid get more than 2/3 of the way down.