Winter is hard on commercial vehicles. To get trucks at peak performance for spring, Bendix Commercial Vehicle Systems offers these maintenance tips.
Spring checks for brake systems
Winter poses a particular threat to wheel-end components. Start spring by looking for corrosion, damage and missing or loose components.
"Post-winter inspections should search for obvious damage and beyond," says Richard Conklin, Bendix's director of engineering, wheel end. "Look closely at components like friction, chambers and automatic slack adjusters. Corrosion, contamination and loss of lubrication can all affect brake performance, even when components appear intact."
Look at the brake friction for cracks, missing material, contamination from oil or grease and minimum thickness. If it's time for new friction, choose linings that meet OEM specifications as well as reduced stopping distance and copper-content requirements. The company says not all friction marked as acceptable under RSD regulations will actually perform to the standard. Friction should be replaced on both sides of the axle for balanced braking and stability.
Brake chambers should be free of damage with the dust plugs properly seated. Measure chamber stroke at each wheel-end to verify proper adjustment. Inspect air lines to make sure they're securely fastened, free of chafing and don't show signs of wear in the mounting mechanism.
"Lubrication is another critical post-winter step," Conklin says. "Moisture left behind from cold weather operation can contribute to corrosion in slack adjusters, cam tubes, shafts and bushings. Applying fresh grease helps displace residual moisture and keep brake operation smooth."
Air disc breaks should be checked for clogs in the rotor cooling fins, which can prevent the rotor from cooling properly. Inspect the chamber for damage or corrosion and check air hoses and clamping mechanisms to confirm they're intact.
"Because opening into the caliper can lead to corrosion, we advise technicians to inspect the boots for punctures or tears, too," Conklin says. "At the same time, check the integrity of the guide pins. Where necessary, repalce parts and make sure the shear adapter cover ins in place and fully seated. The pads should move freely in the carrier. If necessary, remove them and clean the carrier surface with a wire brush. Additionally, check to be sure the brake moves freely on its guidance system."
Inspecting air systems for spring
Clean, dry compressed air is foundational for braking, emissions controls, automated manual transmissions and stability systems, Bendix says.
"Winter exposure can accelerate expected corrosion and material fatigue across air system components like air dryers, air tanks and valve seals, making spring a critical inspection window," says Tony Fischbach, air treatment product group director.
Bendix says to start examining air dryers mounted on the frame rail. They are exposed to the road, which can make them susceptible to corrosion, particularly the seats around the purge and pressure protection valves and the governor connection. Inspect the steel air tanks for corrosion or pinhole leaks, which can lead to unexpected pressure loss.
If needed, replace the air dryer cartridge or the purge valve. Service the pressure protection valves if they are serviceable. Replace the oil-coalescing cartridges if fleet guidelines call for it, remembering to replace them like-for-like.
"During inspections, keep an eye out for cracking or breakage of plastic air line tubing that connects the dryer to the truck's air system," Fischbach says. "Chemicals and temperature cycling can also affect push-to-connect air fittings."
Air system leaks can be present but not seen or heard. Slower system pressurization or more frequent charging cycles can signal underlying issues. Increased charging cycles place additional demand on the air dryer and can shorten cartridge life.
For brake valves
Air-powered brake components depend on valves to regulate pressure and, in turn, those valves rely on properly lubricated seals to regulate airflow. Exposure to moisture and de-icing chemicals can degrade lubrication over time, increasing the risk of sticking or inconsistent brake response.
"Valve-related issues often develop gradually," says Brian Screeton, manager for technical training and service. "Spring inspections give technicians a chance to catch early signs of corrosion-related sticking before they turn into performance complaints."
Anti-freeze compounds can wash away internal lubrication, so Bendix says not to use them unless necessary. Inspect the valves for external air leaks, stiff movement or uneven airflow if de-icing products were used. Test the valve function under operating system pressure to confirm proper performance.
"Now is a good time to replace valves that may be sticking internally," Screeton says. "Some fleets routinely change out air valves as part of post-winter preventive maintenance."
ADAS inspections
Advanced driver assistance systems (ADAS) include antilock braking systems (ABS), electronic stability control (ESC) and collision mitigation. These systems rely on sensors, wiring and electrical connections that are vulnerable to winter weather that can cause moisture intrusion, corrosion and chafing. That can lead to intermittent faults that may not immediately trigger diagnostic alerts, but can result in the system becoming inoperable.
"Wiring and connector issues are a common source of post-winter system problems," says Andy Pilkington, ADAS product group director. "Wiring harnesses — particularly those connected to wheel-speed sensors, radar units and cameras — are especially vulnerable to damage from winter conditions. Once moisture and road salt enter a damaged harness, the resulting trouble codes can persist."
Inspect wiring harnesses connected to wheel-speed sensors, cameras and radar units for frayed insulation, cracked housings or corroded pins. Run a diagnostic scan to help catch active or inactive trouble codes before they escalate into full-system failures.
Check front-mounted radar units for corrosion at their connectors. These components face direct exposure to road spray and chemicals. Radar surfaces obstructed by grime or chemicals should be gently cleaned with approved solutions. Following front-end service or alignment, the steering angle sensor should be recalibrated.
"ESC and collision mitigation rely on accurate steering input data and an uncalibrated steering angle sensor can cause unexpected system responses, such as unintended interventions or incorrect driver alerts," Pilkington says. "It is important to note that a collision mitigation system cannot operate without a fully functional radar unit, so regular inspection of the radar unit is essential."
Tires also play a role in optimum ADAS performance. Tread depth, wear patterns and inflation all influence system operation. Because temperature fluctuations can affect tire pressure, make sure tire pressure monitoring systems (TPMS) are working properly.
