What is the brake hose and how does it work?
The hydraulic steel brake lines that carry brake fluid in your car are bolted to the frame of the vehicle. These metal brake lines must eventually attach to the individual wheel calipers — or wheel cylinders in the case of drum brakes — at all four wheels. Since the wheels constantly move up and down, or left and right in the case of the front wheels, the brake line that attaches to the individual wheel calipers must be highly flexible. Enter the brake hose: a flexible, synthetic, reinforced-rubber hose designed to withstand the 1,000 PSI plus pressures that occur when you apply the brakes. There is at least one brake hose at each wheel position, and sometimes two depending on the suspension design. At the end of each rubber hose are steel connections with seals to maintain a leak-proof connection.
When to consider replacing the brake hose:
- Physical damage. If there are cuts, cracks, abrasions, bulging, or excessive rust at the hose fitting ends, the hose should be replaced.
- Leaks. Seepage at hose fittings, or leaks anywhere along the hose, requires replacement. If there is a leak, or the hose is bulging, you may notice that the brake pedal is lower than usual or spongy.
- Internal hose failure. Occasionally, the lining on the interior of the hose can separate, blocking the flow of hydraulic fluid. This is diagnosed using test gauges. A fluid blockage that prevents the brakes from releasing may manifest itself as dragging brakes or overheated brakes.
- End of Lifetime. Although many brake hoses can last 20 plus years if well-made out of quality materials, after 10 years of service it is best to replace the hoses with new ones for maximum reliability and safety.
How do mechanics replace the brake hose?
- The vehicle is jacked up and safely supported with steel jack stands.
- The wheel and tire assembly are removed.
- A pan is put in place to catch brake fluid.
- Residual pressure in the brake line is relieved by momentarily opening the brake caliper bleeder screw.
- Each hose end is detached. At the caliper, the attachment is often a banjo style bolt with one-time-use copper washers. The attachment at the vehicle frame is typically a flare connection, so a tube nut must be loosened. Once both ends are detached, the hose is removed.
- The new hose is installed using new copper-sealing washers and the factory OEM torque on the tube nut and the banjo bolt.
- Finally, the brake system is bled to remove all air and the vehicle is road tested. A final check for leaks is performed after the road test.
Is it safe to drive with a brake hose problem?
No. Properly working brakes are always essential. If you suspect damage to the brake hoses or see leaks it is a good idea to have a professional evaluate your car’s brakes.
When replacing a brake hose keep in mind:
- If a brake hose is replaced due to aging, the mechanic will check all of the other brake hoses as they may be worn or defective as well.
- Some vehicles have flexible, braided stainless steel brake hoses, or other specially designed hoses. If your car does not have ordinary synthetic rubber hoses, a mechanic will let you know what type of new brake hose you have and what your replacement options are.