Hello. I have a brand new 579 and there is a whooshing sound when I remove the DEF cap. Is this cap supposed to vent? I assume it does. Has anyone had this problem? I assume that the cap is bad. Thank you!
Cap does not vent. Vent is part of the level sensor in the top, should be a 3/8 rubber hose coming off the top down the backside of the tank. You will have to pop the rubber boot on top of the tank off to see
The tank will usually get sucked in under vacuum when the vent is plugged. Follow the hose from the level sender around the back side of the tank. It is likely pinched or blocked somewhere. There is a black plastic filter in line with the hose. As @pushbroom says the cap is not vented.
