Be Prepared When Flooding Impacts School Buses

December 28, 2022

A school bus driving through flooded roads on Sept. 19 in Houston. Hurricane Imelda reportedly dumped 40 inches of rain in over 72 hours. (Photo: Thomas B. Shea/Getty Images.)

With flooding more prominent now than ever before, taking steps to ensure one’s fleet is properly cared for following high waters is paramount for a healthy fleet.

Bendix Commercial Vehicle Systems offered tips for commercial vehicles, such as school buses, exposed to floodwaters. Checks and testing are crucial to getting vehicles safely back on the road. School buses exposed to flooding may require reconditioning air brake, wheel-end and other safety components that have been partially or completely submerged.

The first determination to make is whether the water affecting the vehicle is saltwater or freshwater. If it’s saltwater, Bendix advises fleet managers to immediately begin replacing parts due to the extreme corrosivity of salt water, which can remove lubrication and put certain parts at higher risk for unexpected and premature malfunction. Systems and components must be replaced, including brake system valves, air compressors, air reservoirs, anti-lock brake system (ABS) relays, modulators, and brake actuators.

“Saltwater corrosion is also a threat to wheel ends, since it increases the likelihood of rust jacking and accelerates corrosion of critical surfaces,” said Randy Salvatora, vehicle systems engineering manager for Bendix.

The company also recommends complete replacement of the foundation brakes to prevent a potential future failure.

If it’s unknown whether the water was fresh or salt, fleet managers should play it safe and follow saltwater guidelines, Salvatora added. When replacing any pneumatic system components that have been subjected to flood conditions, disconnect all contaminated air tubes and hoses, flush them with clean water, and blow them out with air pressure to remove contaminants.

To address freshwater damage, begin by carefully power-washing the vehicle, including the foundation brakes. Rubber parts and sealing interfaces should not be directly sprayed with the high-pressure jet as irreparable damage to valves will occur when a high-pressure washer directly sprays exhaust ports.

In the unapplied state, most valves have the delivery open to atmosphere at the exhaust port, so if any exhaust port is submerged, the water has infiltrated the system and can lead to future malfunction.

Appropriate personal protective equipment is recommended while washing or working on flooded vehicles, whether salt water or fresh. The company advises against starting a vehicle if fresh water has entered the air compressor or dryer through the air system intakes.

In checking the air brake system vehicle valving:

- Inspect each component in the pneumatic brake and accessory systems.
- Drain any pressure remaining in the service reservoirs.
- Mark and remove all pneumatic and electrical connectors at each valve.
- Check for evidence of water or contamination inside the connectors, air hoses, or the component itself.
- Carefully use dry compressed air pressure (from a stationary compressor or similar) to blow air through the pneumatic tubes and hoses. Watch for evidence of water or contamination.
- If water or contamination is found inside the component, replace the component. If no evidence of water or contamination is found inside the component, reassemble the component to the associated lines and fittings.
- Repeat this process in inspecting all the valves in the air brake system. Replace any nonfunctioning valves or those showing evidence of ingestion of water or contaminants.
- Inspect tractor and trailer glad hands and the supply and control hoses. Water and contaminants frequently enter the air brake system through unprotected glad hands.

In inspecting the charging system:

Inspect the air intake, compressor, and air dryer for signs of water or contaminant ingestion.
Carefully use dry compressed air pressure (from a stationary compressor or similar) to blow air through the pneumatic tubing and watch for evidence of water or contamination.
Use dry compressed air from a stationary air compressor (or suitable portable unit) to get any residual water out of the service tanks.
Air dryers remove moisture in compressed air, but will not remove moisture that’s present in the system beyond the service tanks.
After reconnecting pneumatic lines, install a new or properly-serviced air dryer to aid in removing any residual moisture from the air inlet.

If signs of moisture or other contamination has been found, all the pneumatic air brake components should be replaced. Once water or contaminants get into any of the air brake components, it’s impossible to completely clear the system without total disassembly, Salvatora explained.

Additionally, examine all wheel ends for water, which increases the possibility of corrosion between drum brake lining material and the shoe table (rust jacking), and can also pool in drums when left standing, increasing the corrosion risk.

Salvatora also recommended checking the integrity of the friction couple between the friction and disc or drum. Remove any fittings and mounting stud nuts, and orient ports downward to verify that no water has entered brake chambers through the air lines. If water is present, replace the actuator. Follow the appropriate wheel-end relubrication procedures, including re-greasing slack adjusters.

Assess the braking/safety electronics components. Bendix ACom PRO software, for instance, is designed to conduct a diagnostic download on systems such as ABS, electronic stability control, and collision mitigation controllers, including any front or side radar units, Salvatora said.

Electronics will validate through self-check in most cases. If the electronic control unit is operable, it will check the necessary solenoids, sensors, and harnesses. Inspect the seven-pin electrical connector interface between the tractor and trailer.

If checks turn up no evidence of water or contamination, conduct a thorough test of the air brake system and ABS before returning the vehicle or trailer to service. Between floodwaters and power-washing, it’s possible that ABS wheel speed sensors may have been moved from their normal position. Push them back into contact with the exciter ring by hand and when the wheel turns, normal wheel-bearing play will adjust the sensor position.

A retest and diagnostic check of the electronic system should be conducted after the initial post-flood testing.

“Additionally, make sure you’re following other vehicle and system manufacturers’ guidelines,” Salvatora concluded. “Flooding can have bumper-to-bumper effects, and you can’t be too careful.”