well here is what I will try just for the sake of it. since they leak air from multiple sources I will inject water in the OUT nipple and try to visualize where how why they pass air backwards. Obviously a sealing issue
maybe I can fix them time permitting.
Could be just those metallic check valves not being seated deep enough . All other component & gaskets are squeezed and sealed by the 4 bolts when mounted. check valves must be the weak point
latest mail from the reseller today confirmed the manufacturer will not respect his warranty (past due) even as I explained that testing water pumps on frozen lakes in Canada was a problem … in March
one more reputation down the drain for 35$ worth ….. of bad pumps
Joining AOMCI has priviledges 🙂
