After nearly killing ourselves during our test drive of the 1966 Buick Electra 225's electrical repairs (that's when we learned it wouldn't stop!) we put it on the lift to investigate the condition of its brake system. We were told that the brakes on the rear axle had been rebuilt several years ago and that the system was flushed and refilled with silicon fluid.
A quick look under the hood revealed the fact that the brake system was the old, single type. That is, the master cylinder feeds one line out to a junction that, in turn, feeds the rear axle and each of the front axles. There is no backup system if there's a catastrophic leak at any wheel, as with newer (post 1970) braking systems.
We saw no obvious problems with the master cylinder (the fluid level was fine) so we removed the wheel drums. The right front brake shoes looked pretty good, with plenty of thickness. However, they were glazed and had dual scrape marks running along their faces, so we pried back the rubber cups on the wheel cylinder. What came out was something like rusty dirt, and that explained what was going on — very little braking pressure was pushing out the shoes because the cylinder was clogged with goo.
On the left side things got worse. Prying back the rubber cups on the cylinder revealed a constant stream of fluid, which explained why the shoes were soaked with the stuff! There was so much leaked fluid that all the dust inside had turned to a greasy muck. We also looked at the flexible lines on both sides and found them to be the originals. Yes, they had lasted 42 years but now they were so stiff that we felt we could break them in two.
Yuck! Could this cylinder be in any worse condition?
The solid brake line on the driver's side disintegrated as we attempted to remove it from the flexible line, further indicating that things were in bad shape. As we suspected, the inner wheel bearing seals on the axle hubs had long since failed and grease was leaking into the brake shoe areas. We'd need some parts....
...and people actually drove the car with this ruptured brake line!
While waiting for the ordered parts to arrive at the local auto store we carefully disassembled the brake shoes, springs, etc., from the backing plates, laying them on the floor in order of assembly. We did this to prevent losing any little pieces but also to have a reference for reassembly. After that we removed the cylinders and flexible lines, and then cleaned the backing plate and insides of the brake drums area thoroughly to get rid of any grease and dirt. We used rags and damp paper towels to do all of this to minimize getting brake dust into the air, just in case the old shoes were asbestos. There's no way around it; this is a filthy job!
Take things apart carefully and you won't go wrong.
The old cylinder is on the way to the trash can.
Cleaning is a no-brainer, but it's important not to breathe in the dust.
Since we had to replace the inner wheel bearing seals we took the opportunity to clean and repack all the wheel bearings. We removed the old seals, cleaned out all the grease in the hubs (lots of it!) and repacked the bearings, being careful to keep each bearing where it originally was placed to prevent uneven wear on the races. After installing the inner bearings we gently tapped the new seals into the hubs and cleaned the shoe-mating surfaces again, just to make sure there was no grease or dirt on them.
Note: some might ask why we didn't elect to clean the old wheel cylinders and hone them out, after which we could install new pistons and seals. The reason we didn't do so is that our experience tell us that such repairs don't last very long before leaks reappear. New cylinders are relatively inexpensive ($60, in this case) and will last many years.
The shoes, lines, seals and wheel cylinders arrived after a few days. While our hands were clean we installed the cylinders onto the backing plates and screwed the flexible lines into them. On the right side of the car we reinstalled the solid brake line into the flexible line's fitting and locked them into place in the bracket on the frame. On the driver's side we removed the old brake line from the junction block under the master cylinder and bent (carefully) our new line to fit. This was installed into the flexible line and everything locked into place in the frame bracket.
We next cleaned our hands again, because we didn't want to get any dirt or fluid onto the new brake shoes. Making sure we oriented the shoes in the correct positions (note that there's a forward shoe and rearward shoe on each side) we installed the spring hold-downs and then stretched the return springs to attach them at the top fixture. We wire-brushed the adjusting mechanisms, lubricated the threads and screwed them to their minimum length, then installed them at the bottom of the shoes. Once the adjuster springs were put into place we were ready for the installation of the drums.
All the parts are installed and ready for the drums.
We replaced the drums and reinserted the outer wheel bearings, tightening them down until there was no "lash" in them when we tilted the drum from top to bottom. We prefer this method of setting pre-load rather than the old (incorrect) one of tightening the nut until the wheel doesn't turn and then backing it off until the cotter pin can be inserted. This was the standard method for many years but it actually runs the bearings too tight and creates heat and premature failure. [Note: Actually, the correct method is to torque the nut to a given specification, but it's very hard to find that spec in shop manuals and other sources. Our method keeps the bearing pre-load snug and prevents wheel-wander due to loose settings. ]
Moving to the inside of the brake backing plates, we turned the teeth on the adjusting mechanism with a flat screwdriver. While rotating the drum we expanded the shoes until there was significant drag on the drums.
Once everything was installed and buttoned-up, we filled the master cylinder with fresh fluid and opened the bleeder on the passenger side (the farthest from the master) and waited until gravity moved fluid down into the cylinder. We then bled the cylinder until no more air bubbles came out. Finally, we did the same to the driver's side cylinder and then checked all the lines and connections for leaks. The master cylinder was refilled and we reinstalled the wheels.
With the wheels installed and lug nuts torqued, we took the car out for a test drive. The brakes performed perfectly and the Buick was, once again, safely on the road.