jerryb Posted July 13, 2007 Share Posted July 13, 2007 I upgraded my 71 240Z brakes from drum to the 280ZX disc and also up to a 15/16th master...BUT.... When the car is not running I have little pressure and with the car on I have less. It stops the car but just at the end of peddle travel. The adjustable piston rod in the master has been lengthened with no effect....well the brakes caught but still no pressue. So I must assume the booster is helping and OK.....? Ive bled the brakes to death with zero change....Bled the master with zero impact....removed the vacume hose...with zero zero zero...nothing. Its a new master with an old splitter. The only thing thats odd is when I press the peddle hard I hear a little pffft coming from either the master or the splitter. NO LEAKS ANYWHERE All worked perfectly prior to this upgrade...and Other than change the master back to the old ...I ran out of things to do! All ideas are appreciated.........One thing..what about that adjustable rod at the peddle comming from the back of the vaccum pod? What will that do? Thanx, Jerry Quote Link to comment Share on other sites More sharing options...
Clifton Posted July 13, 2007 Share Posted July 13, 2007 Do a search for reaction disk. Sounds like that might be it. Quote Link to comment Share on other sites More sharing options...
oatmilk Posted July 13, 2007 Share Posted July 13, 2007 I vote disk as well. I had the exact same symptons. Took off the master vac, went to Autozone, got another one, problems gone. Quote Link to comment Share on other sites More sharing options...
torynich Posted July 13, 2007 Share Posted July 13, 2007 also make sure you mounted your calipers on the correct side so the bleeder is on top so you can actually get all the air out of it. Quote Link to comment Share on other sites More sharing options...
jnjdragracing Posted July 13, 2007 Share Posted July 13, 2007 This is exactly what I was going to say. We did it and had the same symptons. Make sure the calipers are correct. John also make sure you mounted your calipers on the correct side so the bleeder is on top so you can actually get all the air out of it. Quote Link to comment Share on other sites More sharing options...
jerryb Posted July 13, 2007 Author Share Posted July 13, 2007 But ......doesnt the master Vac make it easier to push the pedal down. So wouldnt the pressure go up if it was a reaction disc? Instead the problem persists if I disconnect the the master vac hose from the brake system.altogether...always mushy....what am I misunderstanding! Quote Link to comment Share on other sites More sharing options...
jerryb Posted July 13, 2007 Author Share Posted July 13, 2007 I will also check my calipers the minute I get home just to make sure. I have Toyota calipers up front and understand the importance of this...perhaps I screwed up!! Quote Link to comment Share on other sites More sharing options...
Zmanco Posted July 13, 2007 Share Posted July 13, 2007 Sounds like you still have air in the system. Did you bench bleed the master cylinder before you installed it? If not, no amount of bleeding on the car is going to get all the air out. If your calipers are on correctly, then I'd focus on the M/C. Quote Link to comment Share on other sites More sharing options...
jerryb Posted July 13, 2007 Author Share Posted July 13, 2007 I bled the master on the car...what is bench bleeding. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted July 13, 2007 Share Posted July 13, 2007 There will be air trapped in the M/C. I've only done it once, but IIRC, there was a hose and fittings that came with the M/C that connected the front and rear outlets. I held the m/c in a vise, filled it with brake fluid, and then slowly pumped it until no more bubbles escaped into the reservoirs. Instructions came with the M/C. Perhaps someone else can describe it better? Quote Link to comment Share on other sites More sharing options...
hughdogz Posted July 13, 2007 Share Posted July 13, 2007 I bled the master on the car...what is bench bleeding. Just what ZManco described above...same thing as bleeding it on the car, only you bleed it on a workbench with a vise, etc. Make sure you doen't get any air cracking the bleeders on the side of the m/c under pressure. I had the same problem you're describing when I accidently let my reservoir run dry when bleeding...bleeding the master cured it. You did make sure you have the hole in the adjuster on the threaded rod for the new m/c at roughly the same distance from the mounting flange on the old m/c? Quote Link to comment Share on other sites More sharing options...
jerryb Posted July 13, 2007 Author Share Posted July 13, 2007 Im OK as I did bleed the master (on the car)....not a bubble in sight. And yes the threaded rod is OK. I will check the caliper install as soon as I get home...as I recollect thinking the bleeder screw was low......!!!!! I will know soon enough! Quote Link to comment Share on other sites More sharing options...
J__ Posted July 13, 2007 Share Posted July 13, 2007 i had the exact same problem. at first i checked the reaction disk like everyone said, but it wasnt it. checked the rear calipers and they were the problem. they were on the the correct side, but the bleeder nipple wasnt at 12 o'clock. it was about 10:30, so there a tiny bit of air trapped in the caliper causing the soft pedal. had to remove the lower bolt, tilt the caliper up till the nipple is 12 oclock and bleed it again. make sure u put something between the pads so they have something to clamp onto. im pretty sure that'll gaurantee you to solving this problem Quote Link to comment Share on other sites More sharing options...
jerryb Posted July 14, 2007 Author Share Posted July 14, 2007 Hey John You hit the nail on the head.....I had the calipers on the wrong side. Its not nearly as obvious as the Toyota caliper but obvious nevertheless. I guess I just wasnt paying attention....but if I remember correctly I was paying more attention to the parking brake connection that the caliper side....learn again! Thank for everyone's help! Jerry Quote Link to comment Share on other sites More sharing options...
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