1855 Massey hydraulics

My uncle has got an 1855 and the hydraulics are getting weaker. Used to lift the three point tiller no problem, now it has a hard time. Here is the question. Is there any adjustable relief valve on one of these? We changed the oil and the filter, made no difference. Not sure isf there might be some adjustment or do we have to tear this thing down and rebuild. Any advice is appreciated. Thanks.

Yes. there is a relief valve but those rarely give any sort of problem. More likely than not, the charge pump in the hydro is badly worn and not capable of providing the pressure needed for the 3 pt.

A hydrostatic pump is actually two pumps in one. The true hydro pump is the one that makes the tractor travel forward and backward but it relies upon a "Charge Pump" to circulate oil through it to keep the oil cool and to keep the hydro pump full of oil at all times. It's the charge pump that is tapped into to operate items such as 3 pt hitches, power steering and hydraulic cylinders.

On really rare occasions, the spring in the relief valve can break and the spring will wind into itself, thus reducing the amount of pressure in the system but usually the drop in pressure is so dramatic and instantaneous, you know that something happened. It isn't a gradual thing but a pump wearing out is a gradual thing.

I think that you are going to have to pull the hydro and let a local shop undo the many years of damage. It won't be cheap but a Massey 1855 is one helluva GT that would cost you over ten grand to replace today.

I just talked to him again yesterday and apparently It also has reduced top speed. Goes good when its cold but you only drive at top speed for maybe 700 to a thousand feet and then you notice it slow down slightly. Seems to drive ok at lower speeds though. He feels this may have started after he tryed lifting a homemade blade with the three point, The tractor could barely lift it. Its too heavy. Not sure though because he never tryed top speed for a while after that.

A relief valve is exceeding simple and almost foolproof. Most reliefs consist of a dish shaped seat that fits a standard ball bearing. In the center of the dish is a hole. That hole is the oil bypass. The ball bearing keeps the hole closed by way of a coil spring pushing on the other side of the ball. A screw adjustment is there to vary the amount of spring pressure exerted on the ball and ultimately on the hole in the dished seat.

If this gentleman tried to use his three point hitch to lift something that was too heavy, then the normal result would be having the front wheels come off the ground unless he has a loader on the tractor or some sort of front counterweights. The worst case scenario is that the relief valve would open to allow the high pressure to be controlled to whatever the relief is set at.....which is likely around 750 psi......a fairly low pressure in the overall scheme of things.

The cold hydraulic oil gives him higher ground speeds initially but as the oil warms up, it thins out and escapes around the gears in the charge pump....thus preventing the needed pressure from being reached. Your latest report points at a worn out charge pump.