I just became a member this morning, because I was having the exact same issue as this post, actually I could not have described any better then they did. I replaced the pump basket gasket first, the the union O-ring that hooks the skimmer to the pump, as the air bubbles seemed to be on the suction side. Then I seen some of the replies for you problem, so I thought it must be a pressure problem building up in the sand filter. I went to the pool to work on sand filter, but just as I shut the pump off I noticed a drop of water come from the drain plug on the pump basket. Taped it good & re-installed plug, pump and sand filter are now working normal. Thought I better say something in case your problem was as easy a fix as mine.