Brakes Still Binding

It could be the pressure valve in the piston. It's supposed to hold a small amount of pressure in the wheel cylinders and lines so you don't have to pump them up each time you use them. If it holds to much pressure it could cause the brakes to drag or lock up as they warm up.

CMK - Two questions: 1) Can you describe better how they are "binding?" Are the brakes locking up, or not releasing? and 2) How have you been adjusting your brake shoes - with a feeler gauge or some other method? ...R

Cordell... I'm not totally ruling out the master cylinder problem, but from your descriptions so far it is very possible that you have a brake shoe problem. I think your shoes are not set properly and are "dragging" which causes them to heat up and then you experience the "binding" you described. It is correct that the brake shoes are adjusted via the 4 screws (eccentrics) on the back plate, but the question is how are you using those to get the proper adjustment? Unlike later servo-type brakes, the proper setting for these shoes dictates that the curvature of each shoe must be concentrically aligned to the brake drum. To do this you have to start with the two top and two bottom adjusters in the right place (especially the bottom ones), and then use a feeler gauge through the narrow slot in the drums to get the proper setting at the top and at the bottom of each shoe. Do you have a book or service manual that describes the procedure? If not, PM me and I'll send you a copy of some instructions. Also, be sure to set the push rod on the master cylinder so that you only have a maximum of 1" free travel - you don't want your brakes to engage with the pedal near the floor. Keep your chin up - it will take a little effort, but you will get there. ....R

JeepRoger wrote: Cordell... I'm not totally ruling out the master cylinder problem, but from your descriptions so far it is very possible that you have a brake shoe problem. I think your shoes are not set properly and are "dragging" which causes them to heat up and then you experience the "binding" you described. It is correct that the brake shoes are adjusted via the 4 screws (eccentrics) on the back plate, but the question is how are you using those to get the proper adjustment? Unlike later servo-type brakes, the proper setting for these shoes dictates that the curvature of each shoe must be concentrically aligned to the brake drum. To do this you have to start with the two top and two bottom adjusters in the right place (especially the bottom ones), and then use a feeler gauge through the narrow slot in the drums to get the proper setting at the top and at the bottom of each shoe. Do you have a book or service manual that describes the procedure? If not, PM me and I'll send you a copy of some instructions. Also, be sure to set the push rod on the master cylinder so that you only have a maximum of 1" free travel - you don't want your brakes to engage with the pedal near the floor. Keep your chin up - it will take a little effort, but you will get there. ....R

This sounds like a logical explanation, too. To adjust them, I start with the lower eccentrics, adjust them to the point of least resistance, then adjust the upper eccentrics until it gets to the point of least resistance. I usually adjust the pads individually, start with the forward bottom eccentric, then do the top eccentric coinciding with the bottom one, then move to the rear bottom eccentric on the same backing plate. Hope that made sense... So no, I do not use a feeler gauge.

I try to adjust them so the wheels rotate relatively freely with very little/no resistance. However, I can never seem to get the back ones to the point where I would like, but I didn't think they were bad enough drag like so, perhaps I was wrong?

54ball wrote: I had a 1950 Ford Coupe that did similar. I could feel it like a loss of power. All four wheels were hot. The problem really became apparent when I drove it to the fire station and some one came in saying I left the lights on my Ford. After a few minutes of sitting the brake lights would come on. This master cylinder was by no means new. I did not put it on the car. I had the car about 3 years and it was on the road for about 3 months, at the time. On the Ford you could look down in through the cap and see a tiny port. In the manual this port allowed fluid to flow back from the system into the reservoir. It was not drilled through, a factory imperfection. The dimple was there but it was not drilled through. I drilled it through and the problem was solved.

My brake light will also come on when the brakes bind up, and will stay on until they cool off and the pressure release.

 I'm pretty confident it's that relief hole.  Some of these replacement castings are not as finely finished and or may be unfinished castings from 60 plus years ago. Since the hole is small, a piece of trash could easily block it.

 It's almost like a ghost is putting on the brakes.  Other than pressure build up in the system, what else could it be that sets the brake light off?  If I remember right it took a 1/8 bit.


Edited by 54ball - 22 Nov. 2012 at 7:34am

It's sounding like the problem is in the master cylinder. Either the relief valve or the bleed off hole.

Bruce W wrote: I know you said that you had adjusted the pushrod (several times, sounds like), but are you sure the master cylinder piston is returning all the way? It needs to come all the way back to the snap ring. Dirt, rust, part of the boot, etc could be preventing it from coming all the way back. BW

No, I'm really not 100% sure the piston is making a full come-back. I believe I do have a new master cylinder lying around, somewhere. I'll try to pop that in as soon as I can and drive around my black a dozen times or so... if that doesn't work I'll dig deeper into the brake pad adjustments... sound like they could potentially be part of the problem, too. I'll let everyone know the results as soon as I can.

Cordell

F Bill wrote: I may have mentioned this before ....I used a Crown kit to rebuild my master on my GPW once, and had the same problem as you, as the rebuild parts included some sort of seal or spacer I installed as the diagram showed behind the piston and in front of the snap ring mentioned above. This made the return stroke of the piston so it came back just short of uncovering that little bleedback hole, and it built pressure up as it got warmer. I removed the spacer/seal /whatever the heck it was and the master was able to return to the proper position and not build pressure. I don't know if that part was for another application or what the deal was.   Just another thing to check, and it does the same thing as the too tight pushrod. If you take the top cover and fill plug off and push down on the brakes, you should see a little squirt of fluid out of that hole as the first thing that happens...If no squirt, that hole is either blocked, plugged, or dirty. or there is a piston return issue.

This is good to know. As I recall an "extra piece" going through the rebuild.

Here's the verdict: I replaced the MC, and went from having binding brakes to no brakes... I did bleed them (a lot), however I think they just need a lot more bleeding; at least that's my prediction. In order to get any response from the brakes I really need to pump them...

Edited by CmK - 25 Nov. 2012 at 9:03pm

I've adjusted the push-rod (all the way till it disconnected) and bled the lines a great deal and I still have to pump the pedal at least twice in order to stop/get a solid pedal.

I was going through the manual today (as a last resort ), and noticed you're suppose to fill the master cylinder half way and use the push rod to pump the fluid through the fitting prior to installing it on the frame... I did not do this. Isn't this just to help with the bleeding after it's installed?

Any idea why there is still no pedal?