There is disclosed herein a liquid spray gun which includes an improved heat dissipation system and an improved leakage flow recirculating system.The improved heat dissipation system results from an improved and stronger air flow through the gun housing and around the electromagnetic coils. The improved air flow is created by a venturi or aspiration effect at the spray tip created by the action of the piston pump in spraying liquid at high velocity reducing the air pressure adjacent the tip. The internal portion of the housing communicates with the low pressure area so air in the housing is drawn from the housing to the low pressure area. Vents are provided in the housing adjacent the electromagnetic coils for outside air to be drawn into said housing over said coils and to the low pressure area, thus improving air flow and heat dissipation.