A mobile heating system is disclosed. In one embodiment, the system includes an enclosure defining a plenum that houses a fan and an internal combustion engine. The heating system also includes a hydraulic circuit including a hydraulic pump operably coupled to the internal combustion engine and a first heat exchanger located in the plenum and in fluid communication with the hydraulic pump. The hydraulic circuit also includes a hydraulic motor operably coupled to the fan wherein the hydraulic motor is in fluid communication with and driven by the hydraulic pump. A first valve is disposed between the hydraulic pump and the heat exchanger and is configured to restrict fluid flow and to increase a fluid pumping pressure of the hydraulic pump. A second valve is located upstream of the first valve and is configured to selectively direct hydraulic fluid between the first valve and the hydraulic motor.