Ford 4500 backhoe swing leak

I have a early 70's f0rd 4500 when I use the left swing fluid shoots out the vent or port or whatever it is on the side of that cylinder. I archived it and so far haven found the terminology or diagram. It would be a check valve or vent to allow cylinder to free move to let the other side work. My book covers 555 and appears different. Any info would be appreciated. thanx steve