Bendix Tech Tips: Semi-Trailer Post-Flood Inspection and Reconditioning


Severe weather events, from severe hurricanes to flash floods, can wreak havoc on commercial vehicles and their routes. While stores can take steps to prepare their stores for storms, it’s inevitable that fleets will see some of their assets underwater. When the worst happens, here are some tips on inspecting and possibly reconditioning air brakes, wheel ends, and other safety components that have been partially or completely submerged.

Salt water vs fresh

The first decision to make is whether the water affecting the vehicle was salt water or fresh water. If it was salt water, you will need to start replacing parts immediately due to its extreme corrosiveness, which can eliminate lubrication and put certain parts at a much higher risk of unexpected and premature malfunction. Any brake system valve that has been submerged in salt water should be replaced. Additionally, systems and components including air compressors, air reservoirs, Anti-lock Braking System (ABS) relays, modulators and brake actuators should also be replaced.

“Salt water corrosion is also a threat to wheels because it increases the likelihood of rust and accelerates corrosion of critical surfaces,” said Randy Salvatora, Bendix Engineering Manager, Vehicle Systems. “We therefore recommend the complete replacement of the base brakes to avoid potential future failure. And if it’s unclear whether the water was fresh or salty, play it safe and follow the saltwater guidelines.

Additionally, when replacing pneumatic system components that have been subjected to flooding conditions, disconnect all contaminated air tubing and hoses, flush them with clean water, and blow them out with air. tablet to remove contaminants.

See also: Bendix Tech Tips: Trailer Stability Systems

Freshwater Damage Guidelines

If you are certain that the power unit or trailer has been submerged in fresh water, start by thoroughly pressure washing the vehicle, including the base brakes. Be careful when cleaning: Rubber parts and sealing interfaces must not be sprayed directly with the high-pressure jet. Irreparable damage to the valves will occur when a pressure washer sprays the exhaust ports directly. Proper PPE (Personal Protective Equipment) is recommended when washing or working on flooded vehicles, whether in salt or fresh water. In the unapplied state, most valves have the delivery open to atmosphere at the exhaust port, so if an exhaust port is submerged, water has entered the system and may cause future malfunction.

Not attempt to start a vehicle if fresh water has entered the air compressor or dryer through the air system inlets.

Follow these steps to carefully check the different parts of the air brake system:

vehicle valve

  • Inspect each component of the air brake and accessory systems.
  • Vent any remaining pressure in the service tanks.
  • Mark and remove all pneumatic and electrical connectors from each valve.
  • Check for water or contamination inside connectors, air hoses, or the component itself.
  • Carefully use dry compressed air (from a stationary compressor or similar) to blow air into pneumatic tubes and hoses. Watch for traces of water or contamination.
  • If water or contamination is inside the component, replace the component.
  • If no water or contamination is detected inside the component, reassemble the component to the associated lines and fittings.
  • Repeat this process as you continue to inspect all valves in the air brake system. Replace any valves that are not working or show signs of water ingestion or contaminants.
  • Inspect the tractor and trailer hands free as well as the supply and control hoses. Water and contaminants frequently enter the air brake system through unprotected coupling hands.

charging system

  • Inspect the air intake, compressor, and air dryer for any signs of water ingestion or contaminants.
  • Carefully use dry compressed air pressure (from a stationary compressor or similar) to blow air through the pneumatic tube and watch for water or contamination.
  • Use dry compressed air from a stationary air compressor (or suitable portable unit) to blow residual water out of service tanks.
  • Air dryers remove moisture from compressed air, but they will not remove moisture from the system beyond the service tanks.
  • After reconnecting the air lines, install a new or properly maintained air dryer to help remove any residual moisture from the air inlet.

If you find any signs of moisture or other contamination, all air brake components should be replaced: Once water or contaminants enter any air brake component, it is impossible to completely clean the system without a total disassembly. Also consider the guidance included in TMC Recommended Practice 617A for Contaminant Removal Procedure for Tractor, Trailer, or Cart Air Brake Systems.

Wheel tips and electronics

Examine all wheel bits for water, which increases the risk of corrosion between the drum brake lining material and the pad table (rust) and can also accumulate in the drums when they are are left standing, which increases the risk of corrosion. You will also need to check the integrity of the friction torque between the friction and the disc or drum. Water-filled loading docks might not immediately come to mind as “flooding,” but can certainly have the same impact on certain wheel-end components, such as slack adjusters.

Remove all fittings and mounting stud nuts and point the ports down to check that no water has entered the brake chambers through the air lines. If water is present, replace the actuator. Follow proper wheel relubrication procedures, including regreasing slack adjusters.

Evaluate brake/safety electronics using a diagnostic tool such as Bendix ACom PRO software to perform a diagnostic download on systems such as ABS, ESC (Electronic Stability Control) and collision mitigation controllers, including front or side radar units. The electronics will validate by self-check in most cases. If the Electronic Control Unit (ECU) is working, it will check the solenoids, sensor, harnesses, etc. required. Also be sure to inspect the seven-pin electrical connector interface between the tractor and trailer.

Back on the road and follow-up assistance

If your checks reveal no signs of water or contamination, perform a thorough air brake and ABS test before returning the vehicle or trailer to service. Note that between the flood waters and the pressure wash, the ABS wheel speed sensors may have moved from their normal position. Put them back in contact with the exciter ring by hand, and when the wheel rotates, the normal clearance of the wheel bearing will adjust the position of the sensor.

“We recommend retesting and diagnosing electronic systems after initial post-flood testing,” Salvatora said. “Also, be sure to follow the guidelines of other vehicle and system manufacturers: flooding can have bumper-to-bumper effects, and you can’t be too careful.”


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