Virtually all of today's semis, trucks, and work vehicles utilize air brake systems. Compared to the hydraulic brake systems found in most passenger cars, air brakes have numerous advantages. Such advantages include unlimited supplies of operating fluid, easy coupling attachments, and an ability to brake even when system leaks are present.
Of course, despite their many benefits, air brake systems may still fall prey to a variety of ills. Truck owners should therefore educate themselves about the sorts of things that can go wrong — and how to spot them. This article seeks to improve your diagnostic skills by discussing three common problems affecting air brake systems.
1. Pressure Builds Slowly
The air used inside of an air brake system must exist in a highly pressurized state in order to provide the force needed to stop. The task of pressurizing air falls on the brake system's compressor. The compressor forces more and more air into the compression reservoir until achieving the appropriate pressure.
Each time you apply your brake pedal, air moves out of the reservoir and through your lines to the brakes. This reduces the pressure inside of the reservoir, triggering the compressor to turn on and replenish the air supply. In order for your system to maintain adequate braking ability at all times, the compressor must be able to build pressure at a certain rate.
Pressure build rates must be tested on a regular basis to ensure safe driving. Ideally, a truck with a dual air system should be able to build pressure from 85 psi to 100 psi within 45 seconds. If your truck has failed this test — or if you have simply noticed that your truck seems to be replenishing its pressure more slowly than usual — contact a repair professional immediately.
Slow pressure builds may stem from numerous causes. Leaks as the result of damage in the compressor's intake lines form a common culprit. Likewise, cylinder head gaskets may develop leaks that reduce build rate. Restrictions in the pipe leading from the compressor to the reservoir may also be at fault. Be sure to have a pro evaluate your truck as soon as possible.
2. Excessive Air Leakage Rate
The rate at which your air system loses pressure holds just as much importance at the rate at which it builds pressure. A reservoir that loses pressure too quickly not only puts strain on the compressor but can also leave you without adequate stopping power when you need it most. This issue commonly stems from problems with the valves used to regulate the flow of air out of the reservoir.
All truck drivers should know how to test their air leakage rate. Run your truck long enough for the reservoir to become fully charged, and then turn off the engine and release the parking brake. Now time how quickly the pressure drops. Leakage rates above 2 psi per minute indicate that your system needs professional attention according to TruckingTruth.
3. Oil or Water in Air Reservoir
All air brake systems contain an important component known as the air dryer. The air dryer acts to remove both water and oil from the air before it enters the reservoir. A special filter collects any oil droplets present, while a desiccant bed absorbs any water vapor. Both of these substances can lead to corrosion and other serious problems if allowed to get into your reservoir.
If you have noticed either oil or water when draining your air reservoir, you must identify the underlying problem. The presence of water usually indicates that your air dryer cartridge has reached capacity and needs to be changed. The presence of oil, by contrast, often stems from damaged piston rings in the compressor.
For more information about how to fix your truck's air brake issues, please contact the truck repair professionals at Clutch & Brake Xchange Inc.