Tim240z Posted January 14, 2002 Share Posted January 14, 2002 Having a problem with my stock 73 POS daily driver's brakes: Somewhere, somehow, air is entering the rear braking fuid system. If I bleed the rears, the pedal stays firm for about 100 miles or so of regular driving. After that I have to start pumping them up to get good pressure until I bleed them again. I have a new (reman) master cylinder which is about 1 year old (5000 miles). The brakes bleed well, so I am thinking the master cyl. is not the culprit. The flexible lines are old and should probably be replaced, but are not wet at all. I have checked all the flanges for moisture (brake fluid) but they are all dry. The brake warning light glows dimly in the speedo (always has) but glows brightly when the brakes are in need of bleeding. Any suggestions...should I change out the proportioning valve ( I have one from the V8 project Z that I won't be using)...could that be the problem? Thanks, Tim Quote Link to comment Share on other sites More sharing options...
blueovalz Posted January 14, 2002 Share Posted January 14, 2002 This is exactly what happened to me on only one of my rears (I was using the Turbo calipers, but they basically are all the same design). What was happening was that the adjusting mechanism inside (a tappered piston that seats against a tappered cylinder) gets jammed up (because the two tappered parts get jammmed together). The relationship is much like the synchro rings on a tranny. They ride on a tappered surface too (but don't jam). I polished the surfaces (no good), then gave them a finely sanded finish (no good either). Eventually I purchased a rebuilt pair, and the problem went away. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted January 14, 2002 Share Posted January 14, 2002 BTW, I could remove the calipers, and break the piston free by twisting it in the bore (just as you would do when you replace the pads with newer thicker ones), but a week later the thing was jammed again. You will know if you have the same problem by twisting on yours. If they refuse to turn in the cylinders, and then all of a sudden pop free and start screwing back down into the cylinder like they normally do, then I'll bet this is the same problem you have. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted January 15, 2002 Author Share Posted January 15, 2002 POsted by Dan: quote Sounds like the adjustment mechanism. You use your parking brake? That should keep you in adjustment. You might need to take the drums off and clean and lube the adj. mechanism. Dan, I have pulled the drums off several times and cleaned and lubed each time. The parking brake (I use all the time BTW) is adjusted on the cable to it's fullest amount, but I have to really pull up hard on the brake lever to stop the car from moving on even a slight hill!! Could it be that the adjusters aren't working at all!!?!?? Maybe it's time to put some disks in back. TIm Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted January 15, 2002 Share Posted January 15, 2002 Sounds like the adjustment mechanism. You use your parking brake? That should keep you in adjustment. You might need to take the drums off and clean and lube the adj. mechanism. Quote Link to comment Share on other sites More sharing options...
Guest kc6wfs Posted January 15, 2002 Share Posted January 15, 2002 Get the disks! I can't use my e-brake. I had to slacken the Y cable so the rear U-joint would not hit the rear bracket for the e-brake assy. If that makes sense....... As the car would squat in hard WOT is would rub bad. Any one know of a way to get rid of the rub? Dave Quote Link to comment Share on other sites More sharing options...
Tim240z Posted January 15, 2002 Author Share Posted January 15, 2002 quote Any one know of a way to get rid of the rub? Yeah..install 3000lb/inch springs in the rear...no squat!!!!! Tim Quote Link to comment Share on other sites More sharing options...
Tim240z Posted February 8, 2002 Author Share Posted February 8, 2002 Well after messing around with the rear assemblies for some time now, I finally narrowed it down to the master cylinder. It got to the point where I had ZERO rear brakes, which was somewhat disconcerting!! to say the least. When I couldn't get the rears to bleed anymore, I had to resign myself to the fact that the remanufactured master that I bought 13 months ago (1 year warranty!!)was toast. Anyway I went to the local parts place and dropped $85 for a brand new one and it is SOOOO nice to have a firm pedal again. I am going to have to relearn how to drive the car...no more pumping before every stop! Just though y'al might want an update (probably not, but here it is anyway! ) Tim Quote Link to comment Share on other sites More sharing options...
DavyZ Posted February 8, 2002 Share Posted February 8, 2002 I love to see updates! That way, we know how the problem was resolved and what it finally took to do it!! Davy Quote Link to comment Share on other sites More sharing options...
spotfitz Posted February 9, 2002 Share Posted February 9, 2002 Originally posted by kc6wfs:Get the disks! I can't use my e-brake. I had to slacken the Y cable so the rear U-joint would not hit the rear bracket for the e-brake assy. If that makes sense....... As the car would squat in hard WOT is would rub bad. Any one know of a way to get rid of the rub? Dave Try switching the sides the cables goto and moving that cable tension spring to a higher location. I don't remember where I put my spring, but once I swapped the cables around(your basically crossing them to take some of the length away) the spring did what it was suppose to do.You can just see the angle of the cable in this pic, just behind the caliper. I'm not sure what conversion you have done, but I thought this might help. You will probably have to cut and paste it. http://www.geocities.com/spotfitz/Reardisc.jpg Quote Link to comment Share on other sites More sharing options...
Guest kc6wfs Posted February 9, 2002 Share Posted February 9, 2002 Thanks, I'll try that when my rear disks come in. Tnx, Dave Quote Link to comment Share on other sites More sharing options...
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