Brake System Noise Troubleshooting Tips

Vibration is the main source of noise in a brake system. Noise generally results from rust, distorted or loose components, and/or the wearing or weakening of an original part. As components weaken or become fatigued from the heat and stress generated in the brake system, they no longer fit properly. Any vibration resulting from the pad backing plate to caliper contact points will result in a very audible, irritating noise such as a squeal.

Check these items to troubleshoot noise issues:

Rotors, Wheel Bearings and Hubs

Check the following:

      1. Check for loose or improperly adjusted wheel bearings
      2. Be sure to clean rust/corrosion from hub contact surface
      3. Check mounting hubs for excessive run-out
      4. Wash rotors thoroughly with soap and water and use a bristle brush to remove dust and grit from peaks and valleys on the rotor’s contact surface

Caliper

It is also an important to clean the face of the caliper piston and the surface of the caliper that touches the brake pads. Removing rust and corrosion from these surfaces will help ensure the pads are parallel to the rotor surface.

Caliper Bracket & Hardware

Be sure to clean the caliper/pad mounting bracket. Make sure you focus on the area under hardware clips. Don’t just use a wire brush to clean the surface, be sure you remove all the rust that can prevent the hardware from fitting properly. Replace all anti-rattle clips, springs and pins which can lose their spring tempering due to the higher brake heat. Make sure guide pins are not binding or corroded which would cause misalignment or the brake caliper to not release properly. Ensure proper lubricant is used on the guide pins and hardware when you reassemble the brakes. Make sure the pads do not bind and slide freely when installed in the bracket.

Shim Insulators

The proper use of chemicals on the back of brake pads is also important when preventing unwanted noise from your brake system.

  1. Disc Pads with Integrally Molded Insulators
    Wagner TQ brake pads, with their patented IMI Sound Insulator design, require that NO chemical compounds (EMP, silicone lubricants, moly lube, etc.) be placed on the insulator area of the disc brake pads. Use of chemicals on the insulator may reduce the insulator’s effectiveness.
  2. Disc Pads with Shims Attached
    When installing disc pads with constrained layer shims already attached to the disc pad plate, the technician should put a slight coat of Wagner Silicone Lubricant on the back of the shim. This will aid as an additional noise suppressant.
    Technicians should NOT put any other chemical compound on the back of the shim. Compounds that are tacky might cause the shim to be pulled from the back of the disc pad plate.
  3. Disc Pads without Shims Attached
    When installing disc pads that do not have shims attached (as per OE) the technician should
    utilize the EMP compound that is included in the box with the pads. EMP compound should be put on the back of the disc pad plate where there is contact with the outer caliper fingers or caliper piston when installed.

Break-In Process

An important step in mating the brake pad to the rotor is the break-in process known as burnishing. If the transfer of material is not done correctly, it can lead to vibration and/or noise.

  • No panic stops
  • Perform 20 slow-downs from 50mph to 20mph using light pedal pressure
  • Allow at least 30 seconds between each slow-down session