As the liquid comes from the reservoir, it is pushed between the gear teeth. The oil is moved around to the other side by the action of the drive gear itself and sent through the pressure line. To prevent leakage of oil from the high to the low pressure side from occurring, you can make the gears fit better. You might want to increase the pressure used to move the fluid along. However, the higher the pressure, the higher the friction loading on the teeth.
Oil can leak over and under the gears.
To prevent leakage, you can press the bearings up against the gears. This decreases seepage but this decreases the mechanical efficiency when friction increases. Even though oil acts as lubricant, seizing can occur when oil is drained from the hydraulic system. As F increases, M decreases, thus, the gears and bushing increase in friction and mechanical efficiency decreases. When you increase the pressure on the inlet side of the pump, leakage will increase around the gears.