No idea...sent link to thread to cat tech support:
[FONT=&]It might be the seals or valves leaking internally causing pulsation. Also is the air is getting in the inlet side it will cause cavitation and hammering.[/FONT]
[FONT=&]Thanks,[/FONT]
[FONT=&]Derrick Rewerts[/FONT]
[FONT=&]Technical Sales | Cat Pumps [/FONT]