Why is there abnormal noise after changing brake fluid?
2 Answers
There may be several reasons for abnormal noise after changing brake fluid: 1. Rusty brake pads: The brake discs may produce abnormal noise due to rust or hard spots, which usually occurs when the vehicle first starts moving and improves after a few brake applications. 2. Suspension system failure: The suspension system and pressure bearings may produce abnormal noise. Due to recent cold weather, rubber components harden, and when braking, the rubber parts of the suspension system may produce abnormal noise due to stress, which improves after the car warms up. 3. Brake caliper failure: It is recommended to check if the brake caliper is faulty, which could cause abnormal noise. It is advisable to have it inspected at a 4S shop.
Just after changing the brake fluid in my old car, I noticed a 'hissing' sound when pressing the brakes. The mechanic said it's normal air bleeding. The veteran explained that air can easily enter the lines during fluid changes, like bubbles in a straw, and it takes dozens of brake presses to fully purge it. If the noise persists, the master cylinder's seals need checking—my colleague's car had aged seals leaking air, causing a hiss when compressing air during braking. Another easily overlooked issue is water ingress into the wheel hub bearings; if fluid splashes in during the change, rust can cause a 'humming' noise when rotating, which needs prompt attention.
