YupI'mFrustrated Posted April 10, 2020 Share Posted April 10, 2020 I just finished the rear disk conversion on my 71 240z. I am running 85 Maxima calipers/pads and 82 280zx rotors. Everything fits great and looks fantastic. But then I started bleeding them....I had to replace a hard line that ran from the soft brake tubing to the rear "T" so I knew that there was plenty of air in the lines. I have been bleeding for over an hour and used almost a full liter of brake fluid between both rears and no air is coming out anymore (I bottle bled and vacuum bled). The piston in both calipers won't engage the pads. With the brake pedal fully compressed and the e-brake on, both rotors still spin freely. I have pulled the caliper back off and confirmed that the piston is not pushing out when the brake pedal is pressed. I have a TON of pedal play but figured that was from the front brakes (pulled the calipers off to paint them and haven't bled the lines yet). What am I missing here? Any/all help would be extremely appreciated. Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 10, 2020 Share Posted April 10, 2020 41 minutes ago, YupI'mFrustrated said: I have pulled the caliper back off and confirmed that the piston is not pushing out when the brake pedal is pressed. I have a TON of pedal play but figured that was from the front brakes (pulled the calipers off to paint them and haven't bled the lines yet). Try pumping the pedal. If you have air in the lines pumping will push more fluid in and compress it, causing the pistons to move. It will be a clue. And if one side(end) has air it will affect the other side. So you can't just ignore the fronts and expect the backs to be good. You might want to try a power bleeder, to push or pull fluid through. Are the bleed valve passages at the very top of the caliper piston bores? Sometimes they run a diagonal channel from the bleed screw so you have to look at the casting to see where the actual passage is drilled. It needs to be at the top where the air bubble sits. Pretty common for some of the conversion to have bleed valve orientation problems. You might have to pull a bolt and twist the caliper just for bleeding. Quote Link to comment Share on other sites More sharing options...
Twisted46 Posted April 10, 2020 Share Posted April 10, 2020 Like NewZed said make sure your bleeders are facing up. I had my own brackets made so it wasn't an issue but you can take the caliper off and bleed it with a 2x4 in place of the pads. What does the pedal feel like? I went through 8 bottles of fluid just about every method of bleeding you can imagine and 2 MCs before realizing I fell victim to the reaction disk. Fronts work okay? How are you balancing F/R flow. Quote Link to comment Share on other sites More sharing options...
YupI'mFrustrated Posted April 10, 2020 Author Share Posted April 10, 2020 1 hour ago, NewZed said: Try pumping the pedal. If you have air in the lines pumping will push more fluid in and compress it, causing the pistons to move. It will be a clue. And if one side(end) has air it will affect the other side. So you can't just ignore the fronts and expect the backs to be good. You might want to try a power bleeder, to push or pull fluid through. Are the bleed valve passages at the very top of the caliper piston bores? Sometimes they run a diagonal channel from the bleed screw so you have to look at the casting to see where the actual passage is drilled. It needs to be at the top where the air bubble sits. Pretty common for some of the conversion to have bleed valve orientation problems. You might have to pull a bolt and twist the caliper just for bleeding. The bleed valve passages are diagonal to the top of the piston bores. I went back and rechecked every connection I touched and found a slight leak in a hard line connection. I tightened it up and bled again and the piston finally engaged. After bleeding it though, I pulled the e-brake and could still spin the rotor with some effort. I pulled the caliper off and bled it with the bleeder screw facing straight up and problem solved! Thank you! I never would have thought of bleeding them like that! Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 11, 2020 Share Posted April 11, 2020 It's a well-worn path. Good luck. Quote Link to comment Share on other sites More sharing options...
walkerbk Posted April 11, 2020 Share Posted April 11, 2020 Sounds like your master cylinder lost its prime. If one of your reservoirs went dry, you got some air in the master and you cant get that out by bleeding it at the brakes. You probably need to pull it off and bleed the master cylinder. After the master cylinder is bled, bleed the 4 corners. Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 11, 2020 Share Posted April 11, 2020 17 hours ago, YupI'mFrustrated said: bled it with the bleeder screw facing straight up and problem solved! He said problem solved. He's on to the next one... Quote Link to comment Share on other sites More sharing options...
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