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73-87 Chevy _ GMC Trucks => Brakes, Frame, Steering & Suspension => Brakes and Braking Systems => Topic started by: Warkmeister on June 07, 2018, 11:48:54 am
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Hey guys my 81 k30 CCLB SRW is giving me fits. I got it with a partially completed rear disc conversion and finished that up with the appropriate parts. After a few miles/minutes of driving and fluid heats up, I notice that the right rear brakes starts to drag and eventually almost locks up. I’ve only pushed it once and had to get home, and the brakes started smoking it got so hot.
This last time that it happened I tried separating the master cylinder from the boost unit thinking I might have the wrong master cylinder or too much input pressure from a long rod, but the pressure didn’t change. They were apart about 3/8”. In order to get home, I had to open the bleeder at the caliper just to be able to drive. My question now is do I simply have air in that line and need to perform a full system flush and bleed, do the pad guides just need to be lubed, or do I need to potentially get a new master cylinder as this one doesn’t seem to be relieving pressure when you let off the brakes? I ordered a hydroboost seal kit because I know it weeps a little from the top port just above the mc mounting side.
What area of system failure only affects one wheel? Other brakes may be dragging, but it’s imperceptible due to the severity of the right rear. All rear brake components are new, as is MC, and stainless rear lines from the Tee to calipers.
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Did opening the bleed valve at that rear caliper actually relieve pressure and allow the pads to release the rotor?
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Yes it did. Weird right? I had decreased brake power after that for the few miles back home since it would lose fluid with each brake application, but no more dragging.
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I'd begin with a thorough flush and make sure that there is good fluid flow through all bleed valves and no evidence of residual air. Then remove both rear calipers and thoroughly burnish the slides. Reassemble with a coat of synthetic brake caliper lube on the slides and pin bushings (e.g., Permatex Ceramic Extreme Brake Parts Lubricant (https://www.jegs.com/i/Permatex/775/20354/10002/-1?CAWELAID=230006180039247790&CAGPSPN=pla&CAAGID=15769068431&CATCI=aud-194567928791:pla-221368098071&CATARGETID=230006180037475120&cadevice=c&gclid=EAIaIQobChMI8J-KlKPC2wIVFLvsCh3ONQiUEAYYBSABEgJQSfD_BwE) or similar product). Make sure that no lubricant gets on the friction surfaces of the pads or rotors. You might consider replacing the rubber hose between the fixed lines on the frame and axle, as well. Then reevaluate for symptoms.
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what brake hose did you use to connect the caliper to the brake line?
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Stainless lines from Off-road Designs for the 14 bolt FF rear disc conversion. They were meant for this application and went in perfect.