Miles Posted October 8, 2011 Share Posted October 8, 2011 (edited) 72 240Z with MM vented front and rear brake kits with 280ZX MC. Booster is a new 1975 280Z. Daily driver. Toyota front caliper setup installed five years ago using new remanufactured calipers . Rear setup installed two years ago, but calipers recently started leaking so I replaced them. Reaction disk is in place and MC push rod adjusted correctly. I did multiple bleeds with methodical slow bench bleed of the MC. Tried two new MCs: 280ZX and new Wilwood 1 in. The brakes were bled with a Motive Power bleeder. Normally this works well, but I could not get a solid pedal. I suspected that the 280Zx MC (seven years old) might be leaking so I replaced it. After replacing the original 280Zx MC with a rebuilt unit from Cardone (also tried a new Wilwood 1 in. MC) the brakes remain soft/mushy with pedal that will not pump up.There is long long travel to hard point to about even with gas pedal where pedal becomes hard, but slightly soft. Condition is worse with engine running. After checking all lines for leaks I inspected the front calipes due to pulling right/left while road testing. Inspection of the front calipers does not show any obvious leaks/wetness around the piston dust seals, but I did find a slick black residue on the caliper body below the bottom pistons on each side (see pictures). Is this enough evidence to replace the calipers (five years old)? Edited October 8, 2011 by Miles Quote Link to comment Share on other sites More sharing options...
ritrebor Posted October 8, 2011 Share Posted October 8, 2011 Since you replaced the rear caliper, make sure the rear caliper bleed screw is at the highest point of the caliper. If not you will get a soft pedal as you can't get all the air out. Not sure what the black stuff is on the front caliper since the boots are ok. ritrebor Quote Link to comment Share on other sites More sharing options...
Miles Posted October 8, 2011 Author Share Posted October 8, 2011 I'll try rotating the rear calipers vertical. I need to figure out why the front brakes will sometimes lock either left or right wheel when making a hard stops during road testing. Could be air in the lines? Thanks Quote Link to comment Share on other sites More sharing options...
beermanpete Posted October 9, 2011 Share Posted October 9, 2011 I'll try rotating the rear calipers vertical. I need to figure out why the front brakes will sometimes lock either left or right wheel when making a hard stops during road testing. Could be air in the lines? Thanks If you are at impending lock-up when the one tire locks it is likely due to normal variations in the road surface. Our car does that as well. Your description of the soft pedal sounds like a bad master. If there is no brake fluid leaking out then you have air in the system or 3 bad master cylinders. Quote Link to comment Share on other sites More sharing options...
Miles Posted October 14, 2011 Author Share Posted October 14, 2011 (edited) Turned out that the 280ZX MC that I had rebuilt at Cardone was still leaking. So I installed a Wilwood one inch MC and it too would not hold pressure. I couldn't return the Wilwood because I had to modify the mounting holes in the flange to fit the Datsun bolt pattern on the booster. I bought another Wilwood one inch MC and installed it. I now have a high firm pedal. In addition to the Wilwood MC, I installed a 75 280Z booster which works well with the Wilwood MC and Modern Motorsports (MM) Toyota vented front and 240SX rear disk kits I have had on my car for two years. The combination of the one inch Wilwood MC and the 280Z booster much improves the MM brake kits performance. Pads are Porterfield R4S. The Wilwood one inch MC is a good replacement for the now extinct 280ZX MC. I plan on posting details on the Wilwood MC and 280Z booster install. Edited October 14, 2011 by Miles Quote Link to comment Share on other sites More sharing options...
David GArcia Posted March 1, 2012 Share Posted March 1, 2012 Since you fixed your problem I wanted to ask you a question. To mount the 280z booster did you have to redrill the firewall to acomodate the booster? Quote Link to comment Share on other sites More sharing options...
Miles Posted March 1, 2012 Author Share Posted March 1, 2012 Since you fixed your problem I wanted to ask you a question. To mount the 280z booster did you have to redrill the firewall to acomodate the booster? Yes Quote Link to comment Share on other sites More sharing options...
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