Fluid seals for catheter pump motor assembly

A mechanical circulatory support system to assist a blood pumping function of a heart of a medical patient, the mechanical circulatory support system comprising:

• a percutaneously insertable catheter assembly having an elongate body with a proximal end and a distal end;
• an impeller assembly extendable and retractable from the distal end of the elongate body at a location inside a vasculature of the medical patient;
• a priming apparatus configured to expel air from the impeller assembly prior to insertion of the impeller assembly in the vasculature;
• and
• a percutaneously insertable liquid cooled electric motor directly driving the impeller assembly to pump blood in order to assist the blood pumping function of the heart when the impeller assembly is extended, the motor comprising a flow diverter disposed adjacent to the motor, the flow diverter defining a chamber;
• and
• a first return pathway in fluid communication with the chamber of the flow diverter and configured to direct waste fluid to a reservoir, wherein the first return pathway radially diverges from the catheter assembly at a location distal to at least a portion of the flow diverter.