What a water pump actually does
A water pump is an impeller on a shaft. Belt or timing drive spins it. Coolant hits the vanes and gets thrown through the block. The weep hole is where a dying seal shows.
Crack the cover off a water pump and the job is sitting in the open. A star of vanes on a hub. A snail of iron around them. That is the pump. It is not the radiator. It is not the fan. Spin the shaft and those blades throw coolant. Stop spinning and the mix just sits.
Coolant lands in the eye of the impeller. The vanes sling it out into a volute, and that shove is what walks the mix through the block, the head, and — once the thermostat opens — the radiator. Crossflow or downflow on the core does not matter here. This wheel is the mover. Plastic housing or cast, the ports are just the pipes in and out.
The shaft has to get turned. A lot of pumps wear a hub that takes a pulley, and a belt from the crank does the work. Others sit behind a timing belt or a chain, same vanes, harder to reach. Either way you are looking at a driven flange, not a motor. The seal on that shaft keeps coolant out of the bearing. Between the two is a small hole — the weep. A dying seal drips there on purpose so the leak does not wash the grease. Do not epoxy it shut.
People flush the radiator when the engine cooks. The door never opened, or this wheel never turned. A dry bearing howls. A chewed impeller moves air. The weep crusted green is the early note. The pump is the throw. The thermostat is the door. The radiator is the dump.