It doesn’t take more than few minutes to perform an air brake adjustment and trace any signs of brake malfunction. But before you perform an air brake test, make sure you know exactly what to do. If you have any confusion, go over the CDL manual. Air brakes are entirely different from disc brakes. Moreover, manual slack adjusters adjust the position of air brakes.
Release the Air in the System
During the adjustment process, the vehicle might dislocate from its due position; so choking the tires is a must. Also, maintain the same distance between the push rods, to keep the wheel’s stopping pattern intact. Furthermore, the air brake system needs to be at full pressure, with the emergency brake lowered. Finally, release the brakes using the air valve.
Air Brake Adjustment – Inspect the Pushrod
Take a chalk and mark down the area where the air chamber exhausts. Now, use a tool to pull it out of the brake chamber. Take a measure of the chalk line to the brake chamber. In that way, you will get an exact idea about just how much pressure it requires to compress, to stop your car. A measurement beyond ¾ inch means it’s time for an air brake adjustment.
Adjusting the Pushrod for Manual Adjusters
At this stage, find out the position of the manual slack adjuster near the push rod that was checked earlier. To tune it properly, use the s-cam to see if it’s turning in the right position. Otherwise, you may end up loosening it. You can find out instantly if you are doing it wrong: the push rod should not be pulling out of the air chamber. Once you have successfully located the direction, tighten it up until it resists to finish the Air Brake Adjustment.
At this point, maintain a safe distant between the drum and the linings by reversing the adjuster bolt to ½ from its previous ¼. You have to replace the slack adjuster if the manual adjuster bolt is moveable in both directions, and you don’t know whether you’re tightening or loosening it.
Adjusting the Pushrod for Automatic Adjusters
Manual adjustment is out of the table if you have automatic slack adjusters at your disposal. But yet, review the quality of adjustment, to locate any brake issues before they appear. When using an automatic adjuster, the air pressure level should be above 90 PSI. Besides, keep the parking brake off, along with the brake control and supply valve open.
Now press the brakes completely, and release. Follow this same procedure six times or so. This testing will help adjusters fix any prevailing problems in them. Even after following the steps, the stroke of the push rod may feel excessive. In that case take your car to a repair shop nearby.