monte70car Posted August 18, 2013 Share Posted August 18, 2013 So for a week now I've been hard at work bleeding the brakes after replacing the booster and master cylinder. I bench bleed the master cylinder before putting it on the car so there is no air in that part of the system. Pumping the brake pedal the pedal stays on the floor and it dribbles out of the bleeder screws on both rears bleeders. I checked the front and the fluid comes out in a stream. I'm lost on why the rears want to dribble out fluid. Car had good brakes before the change. Quote Link to comment Share on other sites More sharing options...
MCfan Posted August 18, 2013 Share Posted August 18, 2013 Well, that should teach you not to fix what isn't broken ... jk Don't know if your replacement assembly is new or rebuilt but something very similar happened to me with a rebuilt unit from my local parts house. The rear circuit absolutely refused to prime/bleed and firm up although the front primed and bled just fine. I wasted two full days and too much of my wife's good will (as brake pedal pumper) before I discovered the MC and been rebuilt with the wrong piston. After getting a second rebuilt unit, everything magically primed, bled and solidified as expected. The only other thing I can think to check is the manual relief button on your proportioning valve. Did you block it open while bleeding the front lines and forget to close/unblock it? I'm not sure that would also produce the symptoms you are experiencing but it wouldn't hurt to check. I had to remove the wood shims I used to hold the valve open (shown below) before I could bleed the rear lines. It's probably some entirely different problem, but at least you can eliminate two possible causes. Good luck. Quote Link to comment Share on other sites More sharing options...
black07ss Posted August 18, 2013 Share Posted August 18, 2013 Well, that should teach you not to fix what isn't broken ... Sorry couldn't help it but it is true Quote Link to comment Share on other sites More sharing options...
monte70car Posted August 18, 2013 Author Share Posted August 18, 2013 Dennis I eliminate the manual relief valve as I don't have that one. Got the lines coming off the master cylinder down to theproportioning valve. I got fluid just before the rear end. Quote Link to comment Share on other sites More sharing options...
footballubet Posted August 18, 2013 Share Posted August 18, 2013 Do you have a solid stream at the line before the rear end? Quote Link to comment Share on other sites More sharing options...
monte70car Posted August 18, 2013 Author Share Posted August 18, 2013 Scott I didn't take the line off just undid it to make sure it was getting fluid to that point so I can't say it was a solid stream or not. I did find on line on the proportioning valve that was leaking so I addressed that issue. Went back and pumped the brakes 5 more times and still dribble out the bleeder. Also don't like the pedal as there is no firmness so you can't tell when the pedal is on the floor as it's already there. With the car running you can feel some firmness but in gear the rear just turns. Quote Link to comment Share on other sites More sharing options...
footballubet Posted August 18, 2013 Share Posted August 18, 2013 If all the air is out of the system I'd say the master cylinder has an issue. Quote Link to comment Share on other sites More sharing options...
stangeba Posted August 18, 2013 Share Posted August 18, 2013 Rear rubber hose? (comment on "rebuilt" items) The problem you had with the first RB MC is why I always suggest trying to rebuild, or have your own parts rebuilt. JMO.... Bruce Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted August 18, 2013 Share Posted August 18, 2013 start at the master cylinder to make sure it is pushing fluid to the rear brakes yes...bleed at the out-port of the valve on the proportioning valve at the master cylinder no...valve issue yes...check for fluid coming out of the distribution block on the frame yes...bleed at the fitting to the rubber line at the rear axle yes...replace rubber line if you bench bleed the MC you should know if it was pushing out fluid, you have typical symptoms of the proportioning valve being closed Quote Link to comment Share on other sites More sharing options...
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