Brake Myths Revisited: Brake Hose Restrictions
3. Damaged Brake Hose Can Cause Brakes to Drag
“False, with some truth. This myth usually occurs on a vehicle where the brakes are only stuck on one wheel. The technician tries just about everything and theorizes its a brake hose restriction. Brake hoses are designed with multiple layers to take all kinds of abuse from road debris. The myth states that the liner was damaged creating an internal check valve that doesn’t allow the pressure from releasing the caliper. If this happened, the outer liner would break and leak fluids. The restriction is most likely caused by a stuck emergency break, caliper slides, or even a metering/combination valve problem.”
Above is a quote from the article “Brake Myths: Common Misconceptions.” After the article’s publication, readers gave feedback about how it was wrong about the brake hose restrictions. The number one cause of hose restrictions that readers of the Seven Brake Myths Busted article reported was corrosion of the hose brackets and collars reducing the diameter of the hose. This is actually quite common in the “rust belt”. Another cause brought up by readers was damage by clamps and pliers. Most contaminated brake fluid is in the wheels and removing it through the bleeder screw is a good idea, so why clamp the lines to force it out? This service procedure is not outlined in any current service procedure. This practice first went mainstream when ABS appeared in the late 1980s. Could clamping the lines be causing more damage than good? There’s no clear answer at the present. But if the fluid has debris large enough to block or jam a valve, then the caliper should be replaced.
Most hydraulic brake hoses are made from layers of synthetic rubber and fabric. They are tested to resist collapse, chemicals, and other extreme conditions. Most restrictions and failures of hoses occur at the end attached to the caliper banjo bolt or hard line. It is worst if the hose accidentally supports the caliper’s weight. Brake hoses should be replaced at the first sign of deformation or cracking. In the future brake hoses may be more efficient, stiffer, and have a smaller diameter.