In an aspect, a conveyor system for moving a wheeled structure through a service line is provided. The conveyor system comprises at least one endless belt mounted longitudinally through the service line. The belt has an upper transport portion for moving the vehicle through the service line, and a lower return portion with a support deck below the upper transport portion to support the belt. A liquid introduction system is provided for helping to remove dirt from the belt and/or to remove dirt from between the belt and the support deck.