This is a weird one. The past few days we have had fairly warm weather during the day and night. The other morning it was cool (40's) and cloudy. When the pump timer kicked on at 9am it would not prime. I turned it off and planned on looking at it after work.
After work I cleaned everything up, lubed the O-ring on the strainer basket and the big O-ring around the filter itself where the lid sits. (I have a Pentair NSP60 filter - all stainless steel with an O-ring and 'clamp' around the filter and lid) It was around 70 degrees in the afternoon and when I turned the pump back on it primed and ran fine.
This morning when it was in the 40's again, same thing...would not prime. Turned it off and then back on this afternoon (around 70 degrees) and it magically works again.
I'm guessing something is contracting when it's cool and that's what is causing my air leak. When things warm up, it expands and no more leak, or at least not bad enough to lose prime. I've replaced the O-ring on the strainer basket and ordered the big O-ring for the filter lid today. Any other ideas?