Brake system and bleeding

[RScaletti]

I replaced the rear calipers about two months ago, bled the lines and all was good. Today I bled the front calipers and there was very little air in the lines, and a solid flow of fluid. I used a vacuum bleeder at 20 psi and the gauge hardly moved at all as the fluid was coming out. The fluid was as slow moving as molasses in January, but it is high quality synthetic fluid only two months old.



Now the problem. I figured I would bleed the rear lines quick while I had everything out. The far wheel I bled around 40 times with the vacuum bleeder and and it s pulling mostly air and spitting fluid from the line. I did manage about 7 ounces of fluid in the cup during this process, but still was about half air bubbles. On to the driver side. I bled that line for a good 30 minutes and only ever got about an ounce of fluid out with all of the air.



Now the master cylinder was full when i started, there are no leaks I could find, so where is all of this air coming from. And how do I correct it and have a properly bled system? I will say the front lines not flowing freely on 20 lbs of vacuum is troublesome to me.

 

[B.G. Smith]

I have tried the vacuum bleeders and the problem I had was that the vacuum pulled air in around the bleeder screws threads and I could never tell if the air was out or not. I would much rather have someone on the pedal, much faster and less trouble. Just have to be aware that if you push the pedal down too far it will offset the proportioning valve. If you have a hard pedal I would not sweat it. bg

 

[anpconnors]

Agree w/ B. G. Smith. I replaced master cylinder, Hydro-booster last fall and manually bled brakes with great results.

 

[BDaugherty]

it's very possible your bleeder screw is stopped up. take it all the way out and clean it with a small pick or similar tool.
to keep air from sucking through bleeder screw threads, dab a little grease around the bleeder screw to seal it.

 

[RScaletti]

Good advice. I'll try the flintstone method later today and report back...