How do I create a contained coolant flow model for a school science project?

Hi! My daughter wants to do a science project showing how coolant might be circulated through an astronaut’s space suit.

The idea is to use a simple, hand powered, siphon pump to run blue colored water through clear tubing. The problem comes when you connect the tubing from one end of the pump into the other. There is no air flow in to the line and the fluid won’t move.

What piece of hardware could we add to introduce air into the line, cause the liquid to pump, and keep the system closed (and not spraying “coolant” all over the place?