[ Ref. Wayne Lincoln in 190130 MMDigest ]

Hello!  I had a similar problem a couple years ago.  It seemed
that I checked every hose, valve, seat, spring or screw that could
be adjusted.  While I was at it ("Get out and get under...!"),
I dropped the motor for lubrication.

After reinstalling the motor to the pump, I handled the belt and it
felt smooth and had very little grip left, even thought it visually
appeared to be turning the pump at the correct speed.

I replaced the belt with a new one and suddenly the volume and suction
levels were all back to normal factory spec.  It's worth checking!

Adam Aceto