The Stovebolt Site Forums The Shop Area Driveline 62 C10 master cylinder malfunction ?

Driving home from work today and the front brakes began dragging. By the the time I got home they were hot and smokin. I jacked the front end up and took off the wheels. I could barely move the hub with a prybar between the lugz.
I loosened the brake line at the master cylinder. Released the pressure and the hubs spun free.

Reckon its just a bad master ?

I got it last spring when I was getting the 62 going. It has worked great up till now.

Should have held pressure to the rear brakes as well as the front as all on the same circuit. Front brakes too tight?

I agree with BC59, being there is only one line you would think the rear would too. I don't believe there is another point in the system that would hold pressure, there are no rediual pressure valves, and it were a brake hose it should only effect on side.

You'll need to update us once you change the master cylinder.

Do the rear brakes work at all? A single line master cylinder pressurizes all the brakes equally- - - -unless there's some kind of restriction like the rear flex line being collapsed that prevents pressure from getting to the rear axle, or a pinched steel line to the rear.
Jerry

All the centers of the wheels were hot to the touch, so it was all four. I only jacked up the front and removed the front tires when I got home. I did not lift the rear until after I relieved the fluid pressure.

All four wheels spin free now.

All the shoes were replaced and adjusted correctly about 2 months ago. Soft lines and wheel cylinders in front were replaced by a PO. I replaced rear wheel cylinders and the soft line myself.

The brakes on this truck worked great until yesterday. Hopefully the new master cylinder Im getting tomorrow will have me goin again 👍👍

What was the pedal doing while the brakes were locked up? Was it flopping around loose? Did it return to home position? Did pedal pressure feel normal?

Hy fattboyzz and guys, is there anything that could have prevented the master cylinder piston from returning to its true at rest position, there should be a small clearance between the pushrod and the master cylinder piston. Could the pushrod lock nut have loosened and allowed the pushrod to close the gap between it and the master cylinder piston?

or master cylinder overfilled?

With the master cylinder off check to make sure pedal swings free, spring returns pedal smooth. Overfill m. cyl would expell fluid via vented cap design.

If you enlarge the picture it looks like 2 lines. fattboyzz, did the weather warm up higher than the last few months, just thinking the warm ambient has expanded something to cause the brake application.

Has hydraulic clutch.

OK, that makes sense. Thanks.

Adjust the pedal linkage so the MC returns completely to its fully released position when you're off the brake pedal. There is a relief port at the extreme rearward point of the MC piston travel which must be uncovered to allow pressure to release in the brake lines.
Jerry

The pedal was firmer than usual and all the way up top.

There is generally a gap between home and where the brakes begin. After all my brake work, I had plenty of pedal. Before the new shoes and proper adjustment ,the pedal was down a good bit more. Before new brakes about 1/3 pedal. After new brakes, about 3/4 pedal.

I will be taking it apart Thursday. Then I can see what happened. I picked up the new master cylinder today, but I will check everything out as per yalls comments.

There is a problem with the assembly aspect of master cylinders over the past several years. They get put together in too much of a hurry by unskilled labor. I swear that just about every other one I buy has been bad. It can be very frustrating, more so that when everything is correct. I don't have any hair left to pull, so I have to throw tools now.

If a kit is available,rebuilding a master cylinder is not that difficult. A good wheel Cylinder hone is a must, that and a clean area to work.

I got off work early today and figured I would take the easy route on this. I thought about this first, so I got under the dash and adjusted the rod till there was more play. In neutral and E-brake off, I could roll the truck. Got in and hit the brake. It was a bit lower but was firm. Got out and rolled the truck. No lockdown 👍. Took it for a ride through several subdivisions , applying the brakes at least 50 or 60 times. A few times I jammed em on pretty hard. Other than a slight pull left all was good 👍. Im gonna hang on to the new master cylinder till Im sure things are ok.

Slight pull left probably means your right front shoe needs a little adjustment a click or two.

Yea. Im got my daughter to amazon me one of these to keep in the truck 👍

Well the 62 seems to be good now brakewise 👍

Did a little work with it today. It was about a 35 mile round trip and it done real good !

Thanks for the replies and the good help. I really appreciate it 👍

So was the final conclusion that the pedal linkage was too tight?

Backing off the nut and shortening the rod is the only thing I did ,so yes 👍

I dont know why it worked fine for a couple hundred miles, then acted up. The only difference was new shoes all around a couple months ago. Ive driven it quite a bit since the new shoes. I am just glad to have it rolling good again 👍

Brake adjustment does not, and cannot cause a pull, since none of the brakes do any stopping until all the brakes are in firm contact with the drums. Look for a restriction in a flex line or a wheel cylinder on the side AWAY from the direction of the pull. That allows the affected brake to delay application while the others are already having a stopping effect. Flex lines that collapse on the inside and restrict fluid flow are the most common culprit.
Jerry