Not sure what’s happening here. My 2003 L3830 will not drive or lift the mower. It just stopped working while I was using it. While I was looking around for possible issues…I noticed I do not have the vent tube on the fill cap in the picture. On a whim I plugged the vent tube with my finger and after a few seconds it felt like pressure built and everything worked. It would drive and lift. Shortly after taking my finger off the vent tube….hydraulics stopped working again. I also had a loose belt that was slipping at the same time but I tightened that up and it didn’t correct anything. What could this be? If I get a non vented cap on there would it mess something up?