I replaced my water pump in my Outback a few months ago because it would intermittently pulsate on. It became more pronounced and when I finally decided to really do something about it, I replaced the pump and never had a problem again.... until...
Our trip to South Dakota, we just returned from. But one night at Custer, SD, I woke up to what I thought was the sound of the water pump cycling on again! I woke up from a dead sleep. The water pump is located under a panel right beside the bed, so when it cycles on, I hear it. My wife sleeps through it, but I hear it.
So, I woke up from a dead sleep, sat up in bed, and sure enough, there it was the burrrrrr. burrrrrr, burrrrrrr, sound again. I immediately thought ... OH @*/%!!!!!! and what was worse, it was cycling about once every 3 or 4 seconds! OH my!
I sat there and listened, frustrated as everything, especially since we were 1300 miles from home! Then I realized, the sound was actually coming from the other side of the bed! And then I realized, our Dachshund, sleeping on the other side of my wife in bed was SNORING!
Boy, was I relieved!