The sap is on a timer if the sound lasts more than 120 sec it's not that but if there's something wrong with the sap valve maybe it's taking too long to close and you're getting a whistle thought the valve seat backwards into the sap.

Do you have to be moving or can you just give throttle maybe you need a helper in the cab


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2011 E70 • N55 (me)
2012 E70 • N63 (wife)