Ford 5000 / Roadless 75 hydraulic lift query

[Roadless63]

I have recently "modernised" the fleet with a 1970's Roadless 75 (based on a 5000) and not being familiar with this range of Fords I have got a query regarding the hydraulics having started to use it in anger.
When I pick up an implement and set the height using position control it seems to hunt up and down, this can be somewhat cured by winding the flow control knob down to slow. As soon as the engine is turned off the implement will drop. Is this a sign of internal leakage somewhere? I should add, it does have an assister ram which is connected although I have not verified that it is getting any oil to it!
I imagine all is not quite right however it will do the job at present. Any input appreciated!
Regards
Ed

[Brian]

With the lift raised, pull the AS Valve out, next to the Flow Control.

Stop engine

If the lift stops dropping your problem is Control valve, Unload valve plug, Check valve.

If the lift keeps dropping,Ram cylinder seals, Assister ram, Ram cylinder safety valve.

If you have to take the lift off, the ram cylinder exhaust pipe and return filter hangs below the ram cylinder by about 12". You have to either do a straight lift to clear the axle or hold the lift clear of the axle and undo the banjo bolt holding the pipe to the ram cylinder.

The lift is a very very heavy unit! My back still winces at the thought of lifting one off.

[Roadless63]

Brian, thanks for the input, I have established that pulling out AS control stops it dropping with engine switched off. What are my options from here, is there anything external that can be looked at before ripping off the hyd lid or is it all buried? Is it likely to be a duff O ring somewhere?
Its a shame since rest of the tractor is very straight, 7000hrs and 2 owners from new, runs like a dream, oil & water in all the right places even all the lights work!
Regards
Ed

[Brian]

Your problem is most likely Control valve. You have to remove the top to get to it and it can be a bit tricky to get right if you are fitting a new one. The valves and bushes are all colour coded and have to be carefully fitted using jeweler's polish or Brasso to get a good fit, if not the valve can leak or stick. Just because you have a (say) red valve and a red bush it does not mean that, when the bush is fitted, the valve will still fit it.

When fitted correctly, the valve should just fall through the bush, when lubricated, under its own weight.

Unless the lift is correcting over 30 times per minute it may be best to leave well alone, the lift was never meant to hold up for long periods with the engine stopped, some did but others did not.

[Pascal]

A Roadless 75? Wow, seems like a great tractor. Do you have any pictures?