Brakes, Part I: Master Cylinder

Before I bought the car the owner told me the brakes "needed some work." After getting it here and starting to assess the brakes I learned just how much work they needed: a complete overhaul.

Automotive brakes use a hydraulic system having either disc or drum brakes or a combination of both. Kaiser, like most 1950's American cars, had drum brakes, so the following explanation will be based on that system.

In a hydraulic drum brake system there is a master cylinder connected by steel lines to four wheel cylinders, one at each while. The system is filled with fluid. When the brake pedal is depressed it actuates the piston in the master cylinder, pushing the fluid out of the master cylinder and through the brake lines. This increases the pressure in the (4) wheel cylinders. In each wheel cylinder the increasing pressure forces both pistons (there is one at each end of the wheel cylinder) outward. These pistons, in turn, force brake shoes, which are lined with a friction material, outward and against a steel drum that rotates around them. The car's wheels are bolted to these steel drums, hence stopping them (via the friction created when the shoes press against the drums) stops the car.

The wheel cylinder is at the top. When pressurized fluid enters it, it pushes the pistons outward, pushing the shoes (right and left) outward, which press against the drum (removed here).

In older cars that have sat for a long period of time small amounts of moisture can enter the line, which--if allowed to sit in the same place--can rust cylinders or lines, resulting in leakage. Additionally, the rubber components in the master and wheel cylinders can also deteriorate, leading to loss of sealing power and leakage, which of course means loss of braking power. Besides the hydraulics the brake shoes can become worn thin, or oil-coated (if the wheel cylidners or oil seals are leaking--the oil seal prevents the grease that lubricates the wheel bearings [which the wheels rotate around] from coming into contact with the brake shoes) and the drum can become grooved. I knew from the owner's description that the wheel cylinders, or at least some of them, would have to be rebuilt. I decided I would check over the whole system first to determine what would need to be re-built or replaced, including master cylinder, (4) wheel cylinders, lines, drums and shoes.

I began with the master cylinder. From a visual inspection alone I determined that it needed at least to be rebuilt with new rubber seals. So I ordered a rebuild kit from Kanter_Auto_Products, and disassembled the master cylinder. The first step in the re-building process is to thoroughly clean the cylinder, which I did by first soaking and scrubbing with mineral spirits, followed by a spray application of brake cleaner. These two steps remove all grease and oil. To remove the rust I soaked the cylinder overnight in Evapo-Rust, an amazing product that removes all traces of rust, leaving clean, bare metal. Best of all, the product is non-toxic and biodegradable!

Brake Pedal

Brake pedal removed in preparation to removing master cylinder, which bolts to the frame directly under the brake pedal.

Brake pedal removed

Master cylinder removed

Cleaning the master cylinder with brake cleaner. This is very toxic, and I should have been wearing goggles. All the other times I WAS wearing goggles!

Master cylinder and associated parts before Evapo-Rust

Master cylinder and associated parts after Evapo-Rust

The next step is to hone the master cylinder. Over time small amounts of rust will pit the metal, leaving a rough surface. In order for the seals to work properly you must have a smooth surface, which is achieved through honing. I bought a small hone that can be attached to a hand drill from Harbor_Freight_Tools. In order to achieve a true hone, you must have the master cylinder held stationay on a vise. Normally you would attach the vise to a work bench, but since I don't have one I had to think of an alternative method. So I bought a laminated shelf from Lowes, and a suction mounted vise from Sears. I mounted the vise onto the shelf and anchored it with my knee as I honed.




Here is my vise / honing operation. It worked very well, but unfortunately the master cylinder was beyond repair.



After much honing I realized that the pits in my cylinder were too deep for it to be rebuilt. It would be possible to hone until the pits were completely gone, but by that time the cylinder bore would be too large, which would prevent the seals from sealing properly, so that was not an option. After all of that work, I ended up returning my rebuild kit to Kanter and ordering a new (rebuilt, actually) master cylinder, which is now installed in the car.

New Master Cylinder

New and old side by side

The back of the master cylinder has two fittings that the two brake lines attach to. One of them is a rectangular brass piece that is not fixed, i.e. before you tighten the end fitting, the side fitting (the brass piece) can be placed at any angle relative to the master cylinder you want, but of course it must be placed at the correct angle to line up with the brake line. So before I removed the end fitting I had my wife take a picture of the two fittings to I could get the angle right when I put them back together.

Picture of the angle of the brass fitting

Here I am ready to install the brass fitting on the new master cylinder. I brought the picture up on the computer, measured the angle (crudely) with two rulers (they wouldn't have needed to be rulers, but they served as a convenient straight edge) and...







transferred the angle to the new master cylinder, then tightened the end fitting down with the brass fitting at the correct angle. And it worked!