Brakes locked up

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peterman

peterman

10 Year 15 Year
Joined
Nov 24, 2009
Threads
40
Messages
199
Location
Duxbury, MA
Thought I had my braking issues licked and was driving along today, mild, nothing major, no hills. Truck started getting sluggish. Pulled into a Home Depot, brake smell but no smoke. Got back in to get moving and truck is frozen solid. Pedal rock hard and can't move with the motor. What would cause this? Could my adjustment be so out of wack that one shoe is rubbing and cooked the fluid? Obviously have pressure in the system. Left it overnight to cool down and see if it rolls in the am. Help!

Fj45lv with boosted drums all around, by the way. New shoes, cylinders and master.
 
I had this happen to me. The rod attached to the pedal needed adjustment. Backed off on it a bit and viola!

It would work fine when cold, but as the system heated up, it wouldn't back off far enough and the pedal would get hard as a rock.


This was on a '65 45 LPB with booster added...stock pedals and hanger assembly.

Dan
 
Last edited:
You want some space between the rod and the piston in the master cylinder, but not .250" inch.

:beer:
 
I checked the play at the pedal, and have about 1/4 between the rod and the back of the booster. Could there be something else? Booster problem? Also, when you say between the master and the booster, do you mean the rod inside the master that pushes from the booster to the piston, or the rod from the pedal to the back of the booster?
 
Thanks all for the help. I've monkeyed with this a bunch over the last few weeks. Went through all wheel cylinders again just to make sure none were sticking (amazing how quickly these rust inside), adjusted up the shoes super perfectly, backed the screw pushing on the master almost all the way off, etc. Pedal feels good and haven't had my brakes lock up again but I still do feel the pedal pressure changing over time. It takes a while, maybe 30 minutes or so and gets heavier more quickly with hard braking. So, it doesn't seem like I've really solved the problem, rather I've found the balance to make it all work. Pretty sure I would have a problem again in the mountains (fortunately the old F motor keeps me pretty close to the house). My 40 has no such symptoms but then again, it's totally modern in comparison. Thanks for the assistance getting this far and if anyone has any more advice, fire away!
 
The story ends on a positive note...I ended up griding off 1/4 of the threaded rod in the booster, which allowed me to back it off even more. Then I took up the play at each wheel cylinder and everything is perfect. Stops straight, good pedal pressure, and no more change in pressure or lock up as before. Even with the rod all the way in I couldnt make this happen before. My guess is that some dimension on the aftermarket booster was different from stock (I changed from the single circuit unboosted to a dual circuit boosted setup) and I was still applying pressure with the pedal all the way out. Anyway, problem solved.
 
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