1941 ford coupe under floor master four wheel disc after driving vehicle awhile rear calipers not releasing drag get hot. when car not driven can apply brakes over and over release fine. any suggestions would be great. thank you
I wonder if the calipers are made by the same manufacturer that made the ones on my OT VW. I had to replace each corner in some cases more than once. Try resetting and bleeding the offender and its opposite and see how it goes. If it keeps up You may need to start replacing the rubber line before it. The outside will look fine but inside will collapse and not release the fluid causing drag. If that doesn't work you may need to replace the caliper.
IF YOU ARE USING ONE OF THE COMMERCIALLY AVAILABLE BOOSTER/MASTER COMBO UNITS....ALL I HAVE USED ,THE PUSH PIN BETWEEN THEM IS TOO LONG (NO FREE PLAY).... GRIND IT OFF SAY 1/16" - 1/8"....OR WASHERS UNDER THE MASTER ( IF DIFFICULT TO DISASSEMBLE NOW)..... ANY SLIGHT DRAG ,WILL BUILD HEAT , N LOCK.
are you running a proportional valve? the gm valve sometimes become off centered. Happened to my avatar
thank you for help only thing that is strange to me is that both sides do it can not make it do it on stands in garage only when driven
this sounds like possible because of master was purchased from speed shop magazine would it only do it while driven can not get it to drag on stands in garage thank you for help
I had the exact same problem on my 40 dodge I shortened the rod between the MC and booster no change, I removed the residual valve no change, my problems turned out to be 2 things. One was the pedal arm where it came through the floor was barely touching the side of the opening on one side of it where it comes through the floor and when the body would twist just enough to sometimes to not allow it to fully disengage. The second and I think main problem was the pins on the calipers were sticking although they seemed to be free and were new calipers. I disassembled them and lubricated them all is good now maybe something was changing with the increase in temp causing the pins to bind I do not know but it did solve my problem and I searched and tried many other things before I found this. Like yours I could run it all day on jackstands with no problems.
I had the same problem with my 50 Plymouth when I converted the front to discs with a new underfloor master cylinder. Turns out the c clip that holds the piston in the master had a very small bend in it. As a result the piston was held in about 1/16 of an inch. Seems like it was just enough to create a little drag that magnified with the heating of the brakes. I replaced the c clip and the problem was instantly gone.
I had a '40 Buick when a kid. Exhaust was a little ratty. One morning, the muffler came loose from the exhaust pipe. As an old farm boy, I did the natural thing. Grabbed a piece of bailing wire. Tied the muffler up into the frame, and went on my way. In a few miles, I had no brakes. Made it to work. After work, I commenced to check the brakes , looking for the leak. Nothing. Good brakes. Started home, and a few miles, same thing. Pedal to the floor.. I discovered the exhaust was hitting the front of the muffler, deflecting some upwards onto the brake line, heating and expanding the fluid enough for the rear shoes to drag, causing the drums to expand. When everything cooled down, all was well. Phew!! After all that, do you perhaps have an exhaust too close to a brake line?? Ben
2# or 10# RPV to back disc? bad PV? kinked or crushed brake line? any restriction would be over come by the M/C but not allow pressure to release normally. If both rears have the same problem look for what's common to both. Single line to rear, wrong or bad RPV, PV or damage. I would think if booster related, the same thing would happen to the front disc.
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