Brake lines are fluid-filled pipes and hoses that transmit fluid pressure from the brake pedal to the brake actuators (calipers and brake cylinders). Pressing the brake pedal transmits brake force (pressure approx. 1500 psi) through the fluid-filled brake lines, which actuates the caliper pistons and brake cylinders at the end of the brake pipes, which slows and stops a vehicle.
Brake lines are made up of two separate components, long rigid metal brake pipes that run the length of the vehicle chassis and short flexible rubber hoses which serve to carry brake fluid from the rigid chassis to the dynamic suspension where the brake caliper lives.
Collectively brake pipes and hoses are known as brake lines.
Hard Brake Pipes seen here in green.
Brake Flexi Hoses seen here in orange.
Where are Brake Lines Located?
Hard metal brake lines seen here in green with flexi dynamic rubber hoses see here in orange.
Typically two main brake pipes run from the brake master cylinder located under the hood at the firewall and run to the ABS modulator, where they branch into four separate pipes, one to the edge of the chassis at each wheel brake. Rear brake lines are tagged together and fastened to the underside of the vehicle.
To complete the brake circuit, flexible rubber brake hoses are located at each of the four brake calipers and join the metal brake pipes at the chassis.
Common Brake Line Problems
Brake Pipes – Brake pipes suffer from one main issue, corrosion. Salt-state vehicles are especially prone to premature brake pipe corrosion. Road salt and sticky liquid anti-icing solutions coat the underside of our vehicles winter after winter and while the steel pipes are tough and employ an anticorrosive coating, they eventually succumb to the salt.
Brake pipes are commonly replaced and repaired with copper pipes.
Brake Hoses – Rubber brake hoses (Flexi hose) suffer from perished rubber and corrosion, but often the damage isn’t obvious. Brake hoses are twin lined for safety, and the inner hose may fail and yet offer little or no visual sign of failure. A slight bulge is sometimes visible when a helper activates the brakes, this is often accompanied by a spongy brake pedal feel.
Brake pipes and hoses need regular inspection and generally need replacing within eight years and sooner if you live by the coast or you live in a salt state. Get your brake pipes checked yearly!
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.