Help with Hydraulics

OK, I have no idea WHAT forum this pertains to... This was the closest, although I'm sure it will get moved! I have a hydraulic barber chair, that suddenly isn't "holding" in the fully raised position. It will pump up, but sllloooowwwwlllllly drop back to the lowest position. It takes about ten or 15 minutes to drop; if you pump it up and sit in it, it seems fine. My initial diagosis was that it needed hydraulic jack oil. I lifted the plate that covers the pedestal (snapping the head off the bolt when putting it back... grrrrr). I saw a bolt that looked like it might be covering a reservoir, and two bolts covering what I guess is the brake plate. I would think that wherever one added fluid should have somewhat easy maintenance access, but I can't find anyplace else.