To check for adverse reactions under system pressure/restriction:
Try pinching off the weaker one, if flow improves it means water is flowing back throught it. if flow decreases alot you've pinched the good one, if it decreases a little you've pinched the bad one but all's OK cause it's still giving pressure.
Just make sure you put a good bit of restriction in the 'line' (block & rad, more preferably) before the exit where you see the flow/water come out.
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The only way to check inline is to watch the temps I think, or watch for cavitation, it should'nt make any difference between inline and submersed I think...
**Edited cause I'm an Idiot
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