All four brakes not releasing - advice needed

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69cudaownr

69cudaownr

FABO Gold Member
FABO Gold Member
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Ok guys, All four of my brakes release very slowly. All four wheels get hot due to extra drag. However they do release after some time as I can spin the wheels freely when they cool down. The car has new (rebuilt) Kelsey Hayes callipers, new rear drums and hardware, new distribution valve and new Master Cylinder.
My guess is that it's something to do with the brake fluid not relieving backward somehow after the pedal is released. Anyone have experience with this?
 
Push rod is too long and not allowing the masters piston to fully return. Did you measure and set the rod gap when installing the master cylinder?
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It should be in the FSM and I forget the gap distance. I'm on my way out to the hangar, but I'll run through the shop and read mine on the way there and get back to you later on.... if someone else doesn't have the info before that.
 
That all makes sense to me. Likely the problem. I just found a diagram on page 5-21 of the 69 Service Manual that specifies .910-.920
Thanks for your help.
 
33IMP said:
It could also be the wrong master cylinder with the wrong residual valves. There are different values for drums and discs.
Click to expand...

That’s true, but, there’s no combination that would effect all 4 wheels. A disk residual valve holds less pressure than a drum residual valve. So you could get the disks to drag with a drum residual valve, but neither residual valve should cause the drums to drag.

All 4 wheels effected the same with a disk/drum combo has to be either the master cylinder or combination valve. Or multiple different parts causing the same effect, which is unlikely.
 
Glad I could help.. just got back in from the yard and I had found those .920/.910 dimensions that of course only work for a factory master... but also found a note I wrote with Gap = 0.020 " written in. Glad it was that simple! Get cruising!
 
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