Automotive Brake System Tools

The repair and diagnostic tools for brake service are discussed in the following paragraphs. This discussion does not cover all of the tools you may need; rather, these tools are the most commonly used by the service industry. Details of when and how to use these tools are presented in Section 8 of this guide.

Cleaning Equipment and Containment Systems

Equipment should be used to safely contain asbestos while doing brake work. A negative-pressure enclosure and high-efficiency particulate air (HEPA) vacuum system allow you to clean and inspect brake assemblies while preventing the release of asbestos fibers into the air. A vacuum pump and a HEPA filter keep the enclosure under negative pressure as work is done.

Low-pressure wet cleaning systems wash dirt from the brake assembly and catch the contaminated cleaning agent in a basin. This system uses water mixed with an organic solvent or wetting agent.

The brake assembly is gently flooded to prevent any asbestos-containing brake dust from becoming airborne.

++++ An electronic wheel balancer.

++++ Wheel weight pliers.

++++Brake spring pliers.

===A holddown spring compressor tool.

++++ A drum brake adjustment tool. Reproduced under license from Snap-on Incorporated. All of the marks are marks of their owners.

Holddown Spring and Return Spring Tools

Brake shoe return springs used on drum brakes are very strong and require special tools for removal and installation. Most return spring tools have special sockets and hooks to release and install the spring ends. Some are built like pliers.

Holddown springs for brake shoes are much lighter than return springs, and many such springs can be released and installed by hand. A holddown spring tool looks like a cross between a screwdriver and a nut driver. A specially shaped end grips and rotates the spring retaining washer.

Boot Drivers, Rings, and Pliers

Dust boots attach between the caliper bodies and pistons of disc brakes to keep dirt and moisture out of the caliper bores. A special driver is used to install a dust boot with a metal ring that fits tightly on the caliper body. The circular driver is centered on the boot placed against the caliper and then hit with a hammer to drive the boot into place. Other kinds of dust boots fit into a groove in the caliper bore before the piston is installed. Special rings or pliers are then needed to expand the opening in the dust boot and let the piston slide through it for installation.

Caliper Piston Removal Tools

A caliper piston can usually be slid or twisted out of its bore by hand. Rust and corrosion (especially where road salt is used in the winter) can make piston removal difficult. One simple tool that will help with the job is a set of special pliers that grips the inside of the piston and lets you move it by hand with more force. These pliers work well on pistons that are only mildly stuck.

For a severely stuck caliper piston, a hydraulic piston remover can be used. This tool requires that the caliper be removed from the car and installed in a holding fixture. A hydraulic line is connected to the caliper inlet and a hand-operated pump is used to apply up to 1,000 psi of pressure to loosen the piston.

Because of the danger of spraying brake fluid, always wear eye protection when using this equipment.

Drum Brake Adjusting Tools

Although almost all drum brakes built during the past 30 years have some kind of self-adjuster, the brake shoes still require an initial adjustment after they are installed. The star wheel adjusters of many drum brakes can be adjusted with a flat-blade screwdriver.

Brake adjusting spoons and wire hooks designed for this specific purpose can make the job faster and easier, however.

Brake Cylinder Hones

Cylinder hones are used to clean light rust, corrosion, pits, and built-up residue from the bores of master cylinders, wheel cylinders, and calipers. A hone can be a very useful-sometimes necessary-tool when you have to overhaul a cylinder. A hone will not, how ever, save a cylinder with severe rust or corrosion.

++++A digital caliper for measuring brake disc thickness. Honeywell International Inc.

++++A typical tubing tool set. Snap-on Incorporated.

The most common cylinder hones have two or three replaceable abrasive stones at the ends of spring-loaded arms. Spring tension usually is adjust able to maintain proper stone pressure against the cylinder walls. The other end of the hone is mounted in a drill motor for use, and the hone's flexible shaft lets the motor turn the hone properly without being precisely aligned with the cylinder bore.

Another kind of hone is the brush or ball hone. It has abrasive balls attached to flexible metal brushes that are, in turn, mounted on the hone's flexible shaft.

In use, centrifugal force moves the abrasive balls out ward against the cylinder walls; tension adjustment is not required. A brush hone provides a superior surface finish and is less likely to remove too much metal than a stone hone.

Tubing Tools

The rigid brake lines, or pipes, of the hydraulic system are made of steel tubing to withstand high pressure and to resist damage from vibration, corrosion, and work hardening. Brake lines often can be purchased in preformed lengths to fit specific locations on specific vehicles. Straight brake lines can also be purchased in many lengths and several diameters and bent to fit specific vehicle locations. Even with pre fabricated lines available, you probably will have many occasions to cut and bend steel lines and form flared ends for installation. The common tools you should have are:

¦ A tubing cutter and reamer

¦ Tube benders

¦ A double flaring tool for SAE flares

¦ An International Standards Organization (ISO) flaring tool for European-style ISO flares

Brake Disc Micrometer

A special micrometer should be used to check the thickness of a rotor accurately. A brake disc micrometer has pointed anvils that allow the tip to fit into grooves worn on the rotor. This type of micrometer is read in the same way as other micrometers but is made with a range from 0.300 to 1.300 inches. Digital calipers are also used to measure disc brake thickness.

Drum Micrometer

A drum micrometer is a single-purpose instrument used to measure the inside diameter of a brake drum.

A drum micrometer has two movable arms on a shaft. One arm has a precision dial indicator; the other arm has an outside anvil that fits against the inside of the drum. In use, the arms are secured on the shaft by lock screws that fit into grooves every 1/8-inch (0.125) on the shaft. The dial indicator is graduated in 0.005-inch increments.

Metric drum micrometers work the same way except that the shaft is graduated in 1 cm major increments and the lock screws fit in notches every 2 mm.

Brake Shoe Adjusting Gauge (Calipers)

A brake shoe adjusting gauge is an inside-outside measuring device. This gauge is often called a brake shoe caliper. During drum brake ser vice, the inside part of the gauge is placed inside a newly surfaced drum and expanded to fit the drum diameter. The lock screw is then tightened and the gauge moved to the brake shoes installed on the backing plate. The brake shoes are then adjusted until the outside part of the gauge just slips over them. This action provides a rough adjustment of the brake shoes. Final adjustment must still be done after the drum is installed, but the brake shoe gauge makes the job faster.

Brake Lathes

Brake lathes are special power tools used only for brake service. They are used to turn and resurface brake rotors and drums. Turning involves cutting away very small amounts of metal to restore the surface of the rotor or drum. The traditional brake lathe is an assembly mounted on a stand or workbench.

The bench lathe requires that the drum or rotor be removed from the vehicle and mounted on the lathe for service.

As the drum or rotor is turned on the lathe spindle, a carbide steel cutting bit is passed over the drum or rotor friction surface to remove a small amount of metal. The cutting bit is mounted rigidly on a lathe fixture for precise control as it passes across the friction surface.

An on-car lathe is bolted to the vehicle suspension or mounted on a rigid stand to provide a stable mounting point for the cutting tool. The rotor may be turned by either the vehicle's engine or drive train (for a FWD vehicle) or by an electric motor and drive attachment on the lathe. As the rotor is turned, the lathe cutting tool is moved across both surfaces of the rotor to refinish it. An on-car lathe not only has the obvious advantage of speed, it also rotates the rotor on the vehicle wheel bearings and hub so that these sources of runout, or wobble, are compensated for during the refinishing operation.

++++ A drum micrometer.

++++ A bench brake lathe.

++++ A manifold gauge set.

++++ An on-vehicle disc brake lathe. RTI Technologies, Inc.

++++A drum brake shoe adjusting gauge.

Bleeder Screw Wrenches

Special bleeder screw wrenches often are used to open bleeder screws. Bleeder screw wrenches are small, 6-point box wrenches with strangely offset handles for access to bleeder screws in awkward locations. The 6-point box end grips the screw more securely than a 12-point box wrench can and avoids damage to the screw.

Bleeding Tools

Removing the air from the closed hydraulic brake system is very important. This is done by bleeding the system. Bleeding can be done manually, with a vacuum pump, or with a pressure bleeder. The latter two are preferred because they are quick and very efficient, and the technician can do without an assistant.

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