A cleaning system for cleaning on site an outdoor cooling tube array of an outdoor heat exchanger, the cleaning system comprising a cleaning apparatus that comprises: a truss beam supported to be movable in a first direction, which direction is perpendicular to a longitudinal direction of the truss beam, a nozzle carriage movably held on the truss beam, the nozzle carriage being movable along a nozzle carriage path in the longitudinal direction of the truss beam, a nozzle manifold having a plurality of cleaning nozzles that are mounted to the nozzle carriage, a water intake coupled to the nozzle manifold, and a hydraulic drive (80; 150) including a water inlet (84; 149) and a mechanical power take-off member (96; 106), wherein the mechanical power take-off member is operably coupled to the nozzle carriage for moving the nozzle carriage along the nozzle carriage path, the water inlet (84; 149) being coupled to the water intake, wherein the cleaning apparatus further comprises a first truss beam end support and a second truss beam end support, wherein the truss beam bridges a space between the first and second truss beam end supports (12; 14), wherein when the nozzle carriage is positioned in the space between the first and second truss beam end supports (12; 14), at least some of the plurality of cleaning nozzles are directed downwards within said space, wherein the cleaning system further comprises: a water supply pump for supplying pressurized water from external to the cleaning apparatus, wherein the water supply pump is positioned separate from the cleaning apparatus, and a tube, wherein the tube connects an output of the water supply pump to the water intake of the cleaning apparatus. a truss beam supported to be movable in a first direction, which direction is perpendicular to a longitudinal direction of the truss beam, a nozzle carriage movably held on the truss beam, the nozzle carriage being movable along a nozzle carriage path in the longitudinal direction of the truss beam, a nozzle manifold having a plurality of cleaning nozzles that are mounted to the nozzle carriage, a water intake coupled to the nozzle manifold, and a hydraulic drive (80; 150) including a water inlet (84; 149) and a mechanical power take-off member (96; 106), wherein the mechanical power take-off member is operably coupled to the nozzle carriage for moving the nozzle carriage along the nozzle carriage path, the water inlet (84; 149) being coupled to the water intake, wherein the cleaning apparatus further comprises a first truss beam end support and a second truss beam end support, wherein the truss beam bridges a space between the first and second truss beam end supports (12; 14), wherein when the nozzle carriage is positioned in the space between the first and second truss beam end supports (12; 14), at least some of the plurality of cleaning nozzles are directed downwards within said space, wherein the cleaning system further comprises: a water supply pump for supplying pressurized water from external to the cleaning apparatus, wherein the water supply pump is positioned separate from the cleaning apparatus, and a tube, wherein the tube connects an output of the water supply pump to the water intake of the cleaning apparatus. a water supply pump for supplying pressurized water from external to the cleaning apparatus, wherein the water supply pump is positioned separate from the cleaning apparatus, and a tube, wherein the tube connects an output of the water supply pump to the water intake of the cleaning apparatus.