Ok, this is not rockets science we are dealing with here ... But I have been having nothing but problems with my brakes now that I'm near the end of my rebuild. I don't want to bore you all with all the details of my woes ... But will just start off where I am now.

What I have is all brand new or newly rebuilt as follows:

Master Cylinder (309)
Proportioning valve
Disc Calipers
Pads
All Lines and Hoses
Power Booster
Etc.

So basically the entire brake system is all spanking new. There are no leaks at all and the brakes - front and rear bleed with a smooth clear stream (over and over again) and looks fine - no air. When the brake pedal is hit, the rear brakes work perfectly. No issues. They grab tight and hold.

Now the %^&#&% Front disc is another issue! They don't seem to grab at all. But yet, if I pump the brake pedal 5 or 6 times, the grab a little more with each pump, and then hold tight. Once I let off the brake, the it's the same thing again. 5-6 pumps before the front hold tight. Again the rear are working as designed.

I'm stumped and at wit's end on this. This should be a pretty simple thing and it is beating the crap out of me. I'm about ready to swap out the Master ... Again!

Any and all help/advice would be most appreciated.

I kind of had the reverse happen to me..brakes would grab and not let go...at least until the car cooled down and the vacuum disappeared.."dragging brake"..my problem was with the pin that goes between the master cylinder and the booster was about 3/32" too long. I shimmed the master out from the booster to figure that out. Your problem might be the opposite, your pin is too short...? just my guess.

I kind of had the reverse happen to me..brakes would grab and not let go...at least until the car cooled down and the vacuum disappeared.."dragging brake"..my problem was with the pin that goes between the master cylinder and the booster was about 3/32" too long. I shimmed the master out from the booster to figure that out. Your problem might be the opposite, your pin is too short...? just my guess.

I have the long rod in the power booster now, and have played with the adjustment at the pedal to no avail :(

Sounds like air somewhere in the front system
Did you bench bleed the master cylinder?
Did you pressure bleed the brakes or manual bleed?

Use the search feature in this forum to help you out more, here is a link I found from David Pozzi discussing rod lengths..

http://www.pozziracing.com/brakes.htm#Booster

It does sound like air in the front or the master possible prop valve ( I had two new prop valves bad in a row), I barrowed a mity vac and got done quick that way. ( Its hard to get air to move down hill in fluid) I would strongly sugest now that it has been heated and cooled a couple of times to check every single hydro conection. I have seen a couple times , suck up air under vacume ( letting off the brake) and not leak under preasure untill its a big enough leak. ( Mine leak was at the caliper/ hose connect)

Sounds like air somewhere in the front system
Did you bench bleed the master cylinder?
Did you pressure bleed the brakes or manual bleed?

Yup, bench bleed the master before installation. Brakes were both pressure bled and then manual bled when then seemed to have a problem in the front.

While is is acting like air is in the system, I get a smooth stream of fluid. I can't figure out were air would be coming from, like I said, everything is brand new.

When I put on my front disk brake kit I noticed that one of the caliper mounting brackets was bent and that did not allow the pad to sit flush against the rotor. I sent it back and the new one is flush now so I should have no problems.

Or you can bet getting blow by on the M/C front seal. I have seen this once before on a replacement M/C.

The round valve under the master is a metering valve that does not allow pressure to the front brakes until there is 30-40psi in the line. That could be the problem. The disribution block has no valving and the valve on the frame is a proportioning valve.
I've been lucky and never had a problem...yet

http://www.camaros.org/forum/index.php?topic=1205.0
That's where I got my education.

If you have fluid at all four corners as you claim then your problem may reside in the metering valve. Just because it's new doesn't mean it is good. Try your old one and if you don't have one try TEMPORARILY bypassing it for diagnosis. Without it you have unobsructed fluid to front calipers.

The round valve under the master is a metering valve that does not allow pressure to the front brakes until there is 30-40psi in the line. That could be the problem. The disribution block has no valving and the valve on the frame is a proportioning valve.
I've been lucky and never had a problem...yet

http://www.camaros.org/forum/index.php?topic=1205.0
That's where I got my education.

If you have fluid at all four corners as you claim then your problem may reside in the metering valve. Just because it's new doesn't mean it is good. Try your old one and if you don't have one try TEMPORARILY bypassing it for diagnosis. Without it you have unobsructed fluid to front calipers.

Hmmm ... What you are saying here and the relate thread does make some sense. I'll try replacing the new proportioning valve with my original one (that was replaced due to another issue that turns out wasn't related to the valve) and see if that gives different/better results. If not, I'll get a piece of tubing and try the bypass idea for testing purposes.

Thanks for the for all the advise thus far guys.

Stay tuned ...

the check valves in the master may be incorrect or bad