Water Pump constantly loses Prime

GTX JOHN · 04-24-2015, 04:13 PM

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.

Scott Hamel · 04-24-2015, 06:39 PM

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.

Scott Hamel · 04-24-2015, 07:09 PM

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.

Mike Pearson · 04-24-2015, 08:34 PM

Check the rotation it might be running backwards.

1legjerry · 04-24-2015, 10:56 PM

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

FED 387 · 04-24-2015, 11:34 PM

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??

04-24-2015, 04:13 PM	#1
GTX JOHN VIP Member Join Date: Jun 2009 Location: Boulder City, Nevada 89005 Posts: 2,733 Likes: 2,802 Liked 2,486 Times in 697 Posts	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. __________________ John Irving 741 Stock 741 Super Stock Last edited by GTX JOHN; 04-24-2015 at 04:43 PM.

04-24-2015, 06:39 PM	#2
Scott Hamel Junior Member Join Date: Aug 2013 Location: Averill Park, NY Posts: 11 Likes: 0 Liked 0 Times in 0 Posts	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.

04-24-2015, 07:09 PM	#3
Scott Hamel Junior Member Join Date: Aug 2013 Location: Averill Park, NY Posts: 11 Likes: 0 Liked 0 Times in 0 Posts	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.

04-24-2015, 08:34 PM	#4
Mike Pearson VIP Member Join Date: Mar 2007 Posts: 2,450 Likes: 615 Liked 1,929 Times in 580 Posts	Re: Water Pump constantly loses Prime Check the rotation it might be running backwards. __________________ Mike Pearson 2485 SS

04-24-2015, 10:56 PM	#5
1legjerry Junior Member Join Date: Jul 2011 Posts: 85 Likes: 4 Liked 72 Times in 15 Posts	Re: Water Pump constantly loses Prime Are you using a recovery style catch can? It will help manage the air in the system better.

04-24-2015, 11:34 PM	#6
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,420 Likes: 529 Liked 333 Times in 180 Posts	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??