Jeremy Rowland wrote:Iain, I don't know what would cause the slew to wander but the rams creeping down I suspect would be one of two problems, the first of which is the most likely and that is that oil is leaking back past the spool valve that controls the boom hoist, or the relief valve in that part of the spool block, the other issue could be that although the rams are dry and not leaking oil, one of them could be leaking oil past the seals internally.
When I changed the two boom hoist rams on my 580BT to fit two reconditioned ones, as I knocked the top pin out at the piston end, the ram dropped by itself because the seals were worn.
I would suggest having a word with Tony Flint who was a Hymac trained fitter I will pm his number to you.
Jeremy
Thanks for the pm I will give him a call