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Poor water pump flow?

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Old Mar 31, 2014 | 02:15 PM
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Default Poor water pump flow?

I've been troubleshooting overheating issues with my project for the last 4 months

i'm working on a new radiator and fan setup but tested something over the weekend that has me wondering.

I've been researching that the LS pump should flow roughly 100gpm, so my thinking was with the upper hose disconnected from the radiator (still connected to the pump) and the motor running I should get a pretty decent flow from the upper hose.

with the motor at operating temp, 180+, upper hose removed from radiator, no spill funnel attached to radiator fill neck and full of water, I would barely get a trickle every few seconds from the upper hose.

Here are a couple vids I took, 25 seconds and 15 seconds, but it was a good representation of how my test went for 10 minutes. after 10 minutes, I would say there wasn't a pint of water that was ever pumped out of the water pump.


anyone have anything thoughts or suggestions? I can provide more details on the setup if needed
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Old Mar 31, 2014 | 04:32 PM
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You may have a bad water pump. It'll only move higher volumes at higher engine speeds tho.
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Old Mar 31, 2014 | 04:55 PM
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Is it possible that there is an air bubble in the lower line? If the pump is not receiving any coolant, you risk ruining the dynamic seal and causing the pump to leak out of the weep hole.

Also, I think that 180 is the Start-to Open temp of the Tstat. It is possible that you could just be bypassing all flow to the radiator internally. the explanation of the flow you are seeing at the rad hose would be explained by the 4 holes drilled into the bypass plate that we use to equalize the pressure differential. you could remove the thermostat and perform the same test(cold coolant would be just fine).

Also, I don't know about the 100gpm(not doubting, just don't know), but you will be looking at significantly less flow at idle-enough to make a big mess if you are just yanking it off the rad.

Hope this helps.
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