my buddy's truck did that B-4 he replaced the pump and when it died he put in a new "toyota" pump and it did the same thing. He called me cuz he was    confused

Found a dent  in the metal return line under the truck he musta run over something and it flew up and hit it I reckon

Anyhoo I cut out the "dent" and spliced in a rubber hose and wa-la the noise was gone