Brakes: Part 4 (The “brake job”)

Once you’ve read the previous Parts posts, there is not actually much to say about the service itself. So, let’s focus on some basic procedures and parts quality.

Once you say ‘go’ our technician will start the brake job. The first thing that will be done is to push back the caliper piston with either a small screw press or even a stout screw driver or pry bar. This loosens the pads and allows them to be removed. On drum brakes, the springs and clips are disassembled to remove the shoes. My personal opinion is that hose clamps should be used on all brake jobs, although many mechanics dispute this procedure’s effectiveness. When the piston is pushed back into the caliper, the bleeder screw should be opened first to allow the fluid in the caliper to be released. Otherwise, the fluid will be pushed back into the hose. This could be problematic if the fluid is contaminated because the fluid could be pushed back as far as the master cylinder, causing further damage. A hose clamp can prevent this altogether. In addition, a very small amount of air will get into the brake hose, minimizing the need for excessive brake bleeding to remove trapped air.

Now the rotors and drums can be resurfaced on the lathe. Many mechanics will mount these back on the car and clean them off with brake clean, a fast-drying petroleum based product. However, the best way to clean drums and rotors is to wash them with soap and water. Once the rotor is mounted the technician should apply a non-directional finish with a fine grit sanding wheel. This improves contact with the new brake pad. If the brake hardware is going to be reused it should be cleaned of all debris or washed in a parts washer if they are really bad. Prior to reassembly, the hardware and caliper pins should be lubricated. There are several products on the market, but we use a graphite or silicone based product. In reality, it is better to be lubricated with something rather than nothing. The hardware should be adjusted on a drum system to allow the drum to snugly fit over the shoes. After spinning the drum, it should only rotate about 180°, otherwise, it is too loose and the parking brake will not hold.

Once its all put back together, the piston needs to be pushed back out of the caliper. It is important to depress the brake pedal about an inch at a time until the pedal gets firm. Pushing the pedal to the floor may damage the master cylinder. A vacuum or pressure bleeder should be used to force brake fluid through the lines to remove any contaminated fluid and expel trapped air. If you remember from a previous post, air can be compressed and will result in a spongy feeling pedal. Once this is all done, the technician will take the vehicle for a final test drive to ensure everything is in proper working order.