An air brake monitoring system includes an air brake control module and an air brake monitoring module. The air brake control module is configured to control variation of an amount of pressure in a brake pipe of the vehicle to actuate brakes of a braking system of the vehicle. The air brake monitoring module is configured to obtain a reference replenishment volume corresponding to a volume of air used to recharge the braking system after application of the brakes of the braking system when the braking system when a first amount of brakes are operational, to obtain an actual replenishment volume corresponding to an actual volume of air used to recharge the braking system of the vehicle after a braking activity performed by the vehicle, and to generate a signal based on a comparison of the actual replenishment volume to the reference replenishment volume.