A vital, but often neglected part of the braking system are the Disc brake chambers. This is because they are reliable and usually replaced as a unit if there are any problems.
However, there are things that technicians can do to ensure that customers get the most out of their brake chambers and that repair work maximises brake life. In this article we discuss air disc brake chambers fitted to Hendrickson suspensions; similar principles apply to other manufacturer’s brakes, but details may vary.
Brake chambers can be affected by dirt and corrosion if exposed to water and mud. They can also be damaged from debris and going over rough off-road surfaces. Carefully inspect brake chambers for corrosion and damage.
Damage at the joins between chamber segments are the main cause for concern. So, pay particular attention to these joins. If you need to remove or replace a chamber, keeping an eye on the following points will help complete the job successfully and ensure maximum life from the braking system.
NOTE: If not previously caged, manually cage the brake chamber according to brake chamber manufacturer’s procedures before removing the chamber from the calliper. And then remember to remove the caging bolt before sending the vehicle back into service.
Ensure that only the lowest drain hole in the brake chamber has the rubber plug removed to minimise ingress of any contaminants. On installation, remove the lower housing plug from each chamber. This means that if it is a dual park/emergency brake chamber then two plugs will need to be removed. Failure to remove these plugs will make the calliper release slowly, which will cause brake drag and excessive pad wear.
Lubricate the brake lever ball cup with a white lithium-based grease before installing the brake chamber.
Ensure the brake chamber to calliper seal is in good condition. Apply a smear of grease to this seal, before fitting chamber, to help protect calliper against contaminants.
Clean the brake calliper flange area to ensure a good seal to the brake chamber.
Torque the brake chamber nuts evenly and in steps to ensure correct mounting and engagement of piston rod and ball cup.
NOTE: Damage to the brake lines can occur if they are installed incorrectly or allowed to rub against other parts.
Ensure brake lines are be free of twists and chaffing or rubbing against any other components. Brake air lines must also have sufficient freedom of movement that they do not restrict calliper movement. This problem can become evident as the calliper changes position when the brake pads wear.
Check brake chambers, air lines and connections for air leaks. Ensure that there is at least 620 kPa (90 psi) of pressure available and that the trailer is either raised off the ground or the wheels are chocked to prevent movement.
Apply service brakes. Check for any leaks from air lines, connections or from the service brake diaphragm.
Apply park brakes and check for any leaks from air lines, connections or from the emergency brake chamber diaphragm. Leaks of any nature are unacceptable. If necessary, use soapy water to confirm components are leak free.
For more info, go to www.hendrickson.com.au