I ran my loader today for about four hours and noticed I was a little high with hydraulic fluid (top of sight glass), so I grabbed the oil siphon to pull some out. As I twisted the hyd tank cap off, it had pressure under it (enough to lift my hand up as I unscrewed it). Is that normal? The cap has what looks like a vent hole but the way the rubber ring in the cap is placed on the inside, there is no way pressure can escape. Thanks,
There isn't a pressure relief on that tank. As the oil gets hot the air above it heats up and creates a positive pressure that helps with the implement pump suction. You shouldn't unscrew the cap unless the oil is cold, also the only genuine oil level will be with cold oil.
Makes sense, thanks.