I was trying to figure out what this was also on my '17 and the best I could find were some responses on Dootalk saying it's the RAVEs cycling and it does it as a self cleaning or lubricating feature!? It must not work well because I cleaned my valves this fall and they were full of crud. It might be me making it up, but it seems to do it less now that I cleaned the RAVEs. I doubt that would be an issue on a new sled.