freakmachine said:
okay boyz, i've hit the wall on this one. changed the master cylinder on my 89 mk3, after bench bleeding it i put on the car hooked up all the lines poured more fluid into it and tried to bleed the system, starting from the right rear brake i attempted to draw fluid from the caliper bleeder screw, NOTHING. kept vaccum on it for over 20 minuts and still NADA!!:icon_mad: I've tryed the old shade tree method pump five times and open the bleeder N-A-D-A. I went through the rest of the brakes, and the front two are OK, i went back to the rears and turned the air pressure up to apply more vac pressure. Got a little bit of fluid, and if i keep vac. pressure and close the bleeder, by disconecting the hose from the bleeder screw and if i open the bleeder again it will suck air in! WTF! a year ago i replaced the stock rubber lines with goodridge ones and used the vac. bleeder to bleed the system with out a problem. I thought that maybe the proportioning valve could be giveing me problems, so i removed it cleaned it blew air through it put it back and same problem. I just don't understand it but i know one or more of youzz has had this problem, so some-one please help. thanks guys.:1zhelp:
The passages inside the rear calipers for the bleeders may be plugged with crap. Get a friend to help you. Before applying any pressure to the brake pedal, remove the right rear bleeder screw then have your friend slowly press down on the brake pedal. If you get fluid then the bleeder is clogged. Clean or replacement of bleeder.
If you did not get any fluid, re-install the bleeder and loosen the brake line then have your friend push down the pedal. If you get fluid then the passages in the caliper are clogged - Time for teardown or replacement.
*(hint: if this happens, remove the bleeder try feeding a small wire into the passage to dislodge said crap then bleed appropriately)
If you did not get fluid then the blockage or malfuction is further up the line.
repeat this process for each component until your issue is identified. If a computer controlled component (ABS) seems to be your issue than test as per TSRM.
Just as an aside, vacuum brake bleeders do not apply nearly as much pressure to the system as you would even lightly applying the brake pedal. Nor do they remove all the air from the system. Air in the brake system can be "sticky" for lack of a better term and will adhere to the insides of the lines and the vacuum "bleeders" will suck fluid right past the air. Vacuum systems should only be used as a means of "Flushing/Exchanging" the brake fluid and after being flushed the system should be manually bled as a final step.
*EDIT - Do not bleed your brakes with the engine running.
Hope this helps. Let us know