Ok so I recently changed my front brake shoes, master cylinder/booster and front brake hoses on my '66 cadillac deville. After driving the car the front brakes tighten up to the point I can barely rotate the front wheels by hand and the drums are hot from the drag. I removed the wheels and backed off the adjuster off so I could have proper drag on the brakes. Went for a short drive and the damn things tightened up again. When I changed the shoes. I replaced the rear shoes at the same time and no problems there. Used the old springs and adjusters, they looked ok. The system also bleed out fine and did not run into any clogging. Does anyone know what is going on? Bad wheel cylinders?? Thanks in advance.
If I recall correctly the '66 has a dual chamber master cylinder, could the booster pin be too long (adjusted?) to allow the piston for the front brakes to return fully? Did the wheel cylinders return freely when you replaced the brake shoes? Can you get the brakes to release by cracking a bleeder?
I got the master/booster that is "pre-adjusted", I'm not sure of what the measurement should be for the pin. I trusted it was ok.(should never trust the factory though) The wheel cylinders did seem to release and I didn't see any leaks. They look old though and should just replace them. I have not try cracking the bleeder yet. If it releases when cracked, where's the problem-master cyl?
What is the gap on the booster pin? Like .020 or something? It's been years since I've done a booster/master.
There needs to be some free play between the booster pin and the master cylinder piston. Not much, just enough to make sure the piston is able to fully return to the rear when you let off the brakes. This uncovers the little hole in the master that relieves pressure in the lines. And you should replace or rebuild the front wheel cylinders. The pistons could be sticking, and they're likely to leak also.
The booster/masters I have worked on normally required about .030"-.060" (1/32"/1/16") clearance between the booster push rod and master cylinder primary piston. This was measured with full vacuum, or about 20" Hg, applied to the booster. Make sure the pedal has it's own return spring, and that the pedal can move farther back than necessary to allow full return of the pedal push rod/control valve.
Jacked up the front wheels and noticed after it sat all night the brakes loosened a little bit. Maybe a block in the line somewhere? I then pulled the master cylinder off the booster to see if it would release pressure, no change. I then checked the booster pin length, it's good, almost .030. Ordered new wheel cylinders and self adjusters tonight.
Very likely could be the front brake hoses,might as well put a set of those on while you have it apart.
Yeah, did you assemble them backwards? So the self adjusting feature which is supposed to work on reverse braking is now working on forward motion? I'd think you would need to have the stuff swapped side-for-side, but maybe that happened?
Could be a stuck residual pressure valve, not letting it back down when the peddle is applied. Could be the hoses are collapsing, new does not mean good, just new.
I would still like to see it does while locked up and what happens when you crack a front bleeder, is there a bleeder at the master? That would work too. So change the front wheel cylinders, bleed it and see what happens.
Update Installed new wheel cylinders and adjusters today. Adjusters were good, wheel cylinders seemed locked up. So everything works good, but now the pedal is spongy and pedal goes to the floor. I'm assuming they need to be bleed again. I won't have time to do it until next week. At least one problem is fixed.
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