Intermittent Hydraulics, on 3045

[tha_ulsterscot]

The hyds on the 3045 are not lifting the link arms, the trailer tipping lever is pressurising (engine revs drop while lever is pulled), but the draft/position lever does nothing. PTO shaft is running ??? Just changed the oil in the back end, and put in EP 90. took the seat off tonite, and unscewed the big cap, but the filter inside was dry, and hasn't had oil up there for some time.
The linkage was wiorking before I changed the oil, any help appreciated, could it be something as simple as an airlock ?,
or a sticking valve somewhere ??????????
Thanks in advance Paddy.