SLS on my 1989 300TE

[Ned Kelly]

G'Day guys, i have no SLS function and hoping you can help. My accumulators seem OK, ride seems fine and not rock hard as indicative of shot accumulators. The system seems to recirculate ie; fluid is returning into the revoir. I opened the bleed nipple at the valve and fluid shot up high into the undercarriage so it's under pressure (and covered me in the process). I disconnected the lever from the valve and moved it manually up and down but no change in ride height. What could this be, knackered SLS valve etc? The hydraulic rams have no rubber boots on them but otherwise appear OK and i reckon they are probably ok as far as i can tell visually and that i can't imagine they are a real "wear" item, especially both packing it in at the same time. Any ideas?