Water Pump constantly loses Prime

[Mike Pearson]

Check the rotation it might be running backwards.

[1legjerry]

Are you using a recovery style catch can? It will help manage the air in the system better.

[FED 387]

Ya got air in there!!! the pump should push the water out of the filler neck if its working properly--- maybe have a restriction in the radiator did ya try another pump or radiator??

[GTX JOHN]

I'll try drilling a hole and a petcock in pump tonight......I think you gentleman are right about air lock in system..
Is the proper cap a 7 lb. one....I will be taking heavier cap off also as
that might help purge the system.

Thanks!

[Jeff Teuton]

I took the thing off. We had drilled a hole in the top to vent the thing, finally just put an old style moroso external motor and old pump and problem solved. I don't know if radiator height or what, but it's fixed now.

[NORMAN BARNARD]

John, i had the same trouble with my 27 roadster, radiator was so low in the front that it built a air pocket in the motor. While being filled.

Raised the front of the chassis hi enought while filling it forced the air out thru the radiator and cap.

Problem solved.

[njk53]

I didn't see a statement whether or not you are running a coolant recovery bottle (CRB). If you are running a CRB, the outlet on the bottle should be at the highest point in the cooling system. This will help replenish coolant in the system after you shut the car off. When a cooling system is at temperature/pressure, eveything expands and pushes the coolant into the CRB during operation. When you shut the car off a vacuum occurs pulling the coolant from the bottle back into the radiator filling it. Also, make sure all of your cooling systems hose connections are tight. Leaks will prevent the vacuum event.
From your description, it looks like when you shut the car off when the water pump is working, the coolant that got pushed out of the system during heat expansion isn't being vacuumed back into the system.