My Hayward Northstar SP4000 with a newly added SN1152R motor is making a strange noise that seems to come and go every 30-45 seconds on the high speed. It sounds like air running through the pump or a whooshing noise. I took a video of it with my phone but I think I might be too close to the pump because it doesn't sound as loud as it does on the youtube clip below. The impeller is original but every other part in the pump has been replaced within the past 2 years. It made this noise before the new motor but I always blamed it on the failing motor. Any ideas? Thanks!