Issue link: https://read.dmtmag.com/i/42057
BIG RIG BASICS JOHN BAXTER Stop, look and listen Try these simple tests for finding and fixing air leaks I f you hear the compressor cycling while sitting in traffic with a constant brake pressure or when idling with parking brakes applied, or if you lose all pressure overnight with the engine off, the air supply part of the system is leaking. The compressor should run only 10 percent of the time. If it's running 30 percent or longer, the air supply system is leaking. This needs to be fixed right away or more system maintenance and repair will be necessary. Get the rig into an enclosed, quiet area. Run the engine until the air compressor cuts off. Then, shut down the engine. Stay off the truck. 1 2 3 4 Examine the compressor dis- charge line. Look for cracks in copper lines and for a small residue of moisture and oil. Look at hoses where a line might have rubbed anything, and at all connections, even under the truck. Look at the compressor unloader. Spray soap and water solution on connections. Air leaks will bubble. The two valves in the dryer can leak because of dirt. If this occurs, service the dryer by replac- ing the cartridge, and then clean the valves. Park the truck on a level spot and securely chock the wheels. 26 TRUCKERS NEWS OCTOBER 2011 2 AIR SYSTEM TROUBLESHOOTING Degree of difficulty: 8 out of 10 Tools needed: A spray bottle of soap and water, wheel chocks, and either a helper or a piece of wood cut to hold the treadle valve down to apply the brakes as you inspect the system. 3 Have a helper engage and disen- gage the parking brake repeatedly so you can watch the spring brakes on each axle retract. All the spring brakes should retract rapidly and at about the same speed and distance. 4 5 One retracting slowly or partially means a leak nearby in the parking brake air circuit. If this doesn't reveal a prob- lem, walk around and crawl under the vehicle to use soapy