Ok, so either I am doing something wrong, or just unlucky. I have 1941 Ford Brakes/backing plates. Original p***enger rear wheel cylinder started leaking, so bought a new one. I tear everything down, remove drum, springs, release shoes, removed old wheel cylinder, install new one to backing plate. At this point is where I have concern. I take the brake shoes and rotate them back into position making contact with the cylinder/piston. As soon as I put the return spring back on, it compresses the piston completely, and rubber cups go to maximum stretch. Still no problem (as far as I know) ****on everything up, seems good.A few days later, I have the cup leaking again. This is my third wheel cylinder. So am I doing something wrong, or just unlucky? is there a way to prime the cylinder so it doesnt retract fully, or is that just the way it is and wheel cylinders today are junk? I have bought the cylinders from two different vendors and two different brands. Help...please.
No you are doing it incorrectly, There is nothing wrong with the wheel cylinder you have you will just have to take a different approach to installing it. The wheel cylinders are not junk they are just made different than you would expect and issues develop from that. I have posted this before on the Ford Barn web site but cant remember if I posted it here. I also have addressed the design issue with a couple of the wheel cylinder mfgs so the issue is known. If they change it who knows! First, some of the new design wheel cylinders have the inlet port indexed too far up in the large bore of the wheel cylinder. Installing the spring from the big end bore to the small end bore with a fluid empty wheel cylinder pushes the big piston rearward far enough to push the cup seal past the port opening. When you go to put fluid in the cylinder the seal is not complete and the cylinder leaks. There is no problem reusing the cylinder you just have to use a little care in installation. Just remove the leaking cylinder and dis***emble and completely clean the unit with brake clean and then pre lube the bore with some brake fluid and re***emble the wheel cylinder starting with the small bore side the same way you disasembled it. Plug the inlet line fitting and then fill the wheel cylinder with brake fluid to a level just below the inlet port on the large bore side of the cylinder, carefully complete ***embly of the wheel cylinder large bore piston and seals. Install the wheel cylinder in the backing plate and hook up the brake line. Take a C clamp and restrain the pistons so that they will not expand past the end of the cylinder and bleed the brake cylinder of air. Doing it this way will give you a fully charged wheel cylinder. Now to hook up the brake shoe spring, hook the brake spring on the small piston shoe and stretch it to the large piston shoe and clip in place. Connecting in this fashion will and prevent the large port seal cup from moving past the inlet port under tension and producing a leak. Now re install brake drums and follow the procedure for adjusting the brakes. After setting the brake adjustment to lock re bleed the brakes and complete the adjustment procedure. As added security to prevent the shoes from collapsing the wheel cyinders too far make sure the upper shoe anchor rotators are fully rotated outward. This prevents the shoes from contracting to far. You can rotate the anchors inward after the spring is attached to install the drum.
If the wheel cylinders are still leaking try this. remove the drum not touching any adjustment. Make sure the pistons are all the way in. The measurement you should get maybe 1/8" less then drum ID What happens often is the shoes lining are to long. You should be 1/2" from first rivet. Chamfer to depth 1/8" back 1/2" on angle.
Hey ****, a follow up question. I used a vacuum bleeder on my 40 brakes and the fronts started leaking. I'm guessing the vacuum pulled the cups/cup out of their bores? Haven't taken it apart yet, but they are new Wagner wheel cylinders. I'll use your system this time around.
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