Water Pump constantly loses Prime
 

Big Block Mopar with CSI Pump and Aluminum
crossflow radiator.

Every time we run the system after 10 Minutes or more
sitting time.....it has lost prime and does not move a drop of water.

To prime I squeeze the hose for up to 30 seconds or put a small amount
of compressed air (10 PSI) thru cap on radiator with a rag around hose. I
can not find any leak.

I have flushed entire system several times and back flushed and
was not unusually dirty for a few year old racecar.

Replaced hoses with molded ones thinking they might be the issue.

Is there any utility to raising the stat housing with an extension and
putting the cap there like a dragster.

Everything is in OEM location and current cap is highest point in system.

Pump circulates like crazy once it is primed.

Thanks,
Racing next week and a new car to us.

Re: Water Pump constantly loses Prime
 

John, I had a similar problem with our T/S car. You have a lot of air in the cooling system and once the pump gets loaded up with air no more circulation. I installed a petcock in the top of the water pump housing so I could bleed air out of it. Our radiator cap is in the upper hose and I found that if I ran the pump with the cap off it would actually pull air into the system there also. I never run the pump with the cap off now. I also bleed the system at the heads. Not sure if you could do that in your situation. You may have to bleed it a number of times to get all the air out. Always do your bleeding with the pump off. I would also pressure test the system to make sure you don't have a head gasket or head problem letting combustion pressure into the cooing system.

Re: Water Pump constantly loses Prime
 

John, I forgot the most important thing. I use a Lisle Spill Free Cooling system funnel when I'm bleeding and filling the system. It gets the fill level above the heads and helps a great deal with the whole procedure. Fill the funnel to the top and turn on the pump.

Re: Water Pump constantly loses Prime
 

Check the rotation it might be running backwards.

Re: Water Pump constantly loses Prime
 

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

Re: Water Pump constantly loses Prime
 

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??

Re: Water Pump constantly loses Prime
 

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!

Re: Water Pump constantly loses Prime
 

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.

Re: Water Pump constantly loses Prime
 

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.

Re: Water Pump constantly loses Prime
 

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.