Massey Ferguson 500-series steering pump is driven by the camsaft gear inside engine's timing case. Pump has integrated small tank for hydraulic oil. This pump can be replaced with 300-series tandem pump, that sucks oil from transmission central housing. Tandem pump's low pressure part would feed steering orbitrol and other pump section give oil to auxiliary hydraulics independently of linkage.
System could look like this. In this 390 hydraulic pump there is no pressure relief valve, this valve in the picture is something else. Pressure is limited in the orbitrol, Danfoss OSP C 125 ON (4-WD). On the other hand 565 orbitrol Danfoss OSP B 80 ON doesn't have this kind of valve, the pressure relief valve is in the pump itself. So if we change the pump, we must limit pressure some other way in order not to brutalize the steering system.
I've explained MF390 hydraulics here.
MF 390 has a hole for suction pipe on the corner of the central housing, unlike this 565. Only larger opening in the transmission housing is that 3 inch hole at the bottom, that's for cleaning of linkage pump's suction filter. It's closed with triangular cover bolted on.
Maybe with a proper design of the art suction tube we could use this opening to get our vital oil without cavitation risk on the pumps, hmmm.
To keep ground clearance high enough, suction tube should look like this. In the near end of the tube is a cylinder for 390 style suction filter.
There is plenty of room under bonnet to insert a return filter in steering hydraulic circuit. In at least 2WD 565 the hoses between orbi and pump are rather small in diameter, probably 1/4 inch. Lower is pressure line to orbitrol, higher is return. New pump produces over 20 l/min flow so I change the hoses to bigger ones. I assume orbitrol is large enough to let oil thru.
In my workshop I manufactured suction tube with integrated filter case. Also made a cover with a pipe outlet for 1 inch inner diameter suction hose. At the base of pipe stump underside of the cover there is a small bore to empty air pocket in the case.
I was recycling steel remains of Finnish-made old farm machinery. The rectangular inlet pipe is 20x40 mm inside and 30x50 mm outside. Pipe was intended to be straight, but I remembered the measurement wrong and made it too long. I had to shorten it and then made also a slight curve in the middle. That was good, because tube came now closer to tractor body.
Filter element in the case and normal cork gasket to other end. Element is centred with a pipe stump in the cover.
Trying out the cover. Filter element could be the type used in 565 linkage pump. This element is the one specifically meant for 390 tandem pump's suction line. Spring in the bottom keeps it steady against the cover.
Suction tube from behind. Case for suction filter went even closer to tractor body than was intended to. Tube can be anchored to extension block jointing bolts as hard as is necessary. Bolts for triangular cover are short and small (UNC 5/16). I bought a bit longer bolts for it. Also bought couple longer UNF 7/16-bolts for jointing to fasten the filter case end. Body jointing has also bolts with rougher thread (UNC 7/16), when the thread is machined in casting.
Suction tube as attacking stump sees it.
Pump's place on the side of Perkins engine and gear wheel's opening to timing case.
The pumps, old and new. 565 drive gear wheel is with 14 teeth and 390 with 16 teeth. Fastening differs slightly so that pumps can be changed, althought gears are with different diameter.
The tandem pump bolted on, fits alright at least with one-legged alternator. Angle connectors with M18 thread must be installed beforehand. Inputs are connected internally. Input for low pressure pump section has 3/4 inch (19 mm) hole for flange connection. Suction hose from self-made filter unit is connected here. Auxiliary pump section input is connected to filter in orbi's return line.
Hoses assembled, banjo connector in orbi's pressure hose. Auxiliary hydraulics pressure hose is lead behind the fuel filtration unit to valve table under cabin floor. Suction hose passes cabin support bar with a curve downwards. Air comes away when front axle is driven uphill.
There is now filter in orbitrol return line in the style of 390. This 8-speed 565 doesn't originally have other filtration than sparse suction filter. T-connector by the filter is for spill line of the relief valve. Bolts for the cylinder head cover were loose and oil leaked. That's why Perkins is so dirty.
I trimmed my separate relief valve directly to orbitrol input to make my hoses meet. There is a pressure gauge temporarily in line to adjust maximum pressure. I adjusted it to 110 bar that felt convenient and wheels turned nicely while standing still.
Before that I had to take a step back with disappointed feelings, cause steering didn't work at all. Also auxiliary pump's output was white foam, that came out with sharp rattling noise. This was easy to notice cause pressure output hose was lead to opened transmission housing oil reservoir. The lift cover was earlier removed to make linkage renovation.
I bypassed the steering circuit by leading oil directly to other pump's inlet, with no clearness to my milkshake. Thought a while and came to mind, that pump can intake air also from inside engine timing case pass axle sealants. To verify this theory the tandem pump had to be dismantled and repaired. More on page tandem pump repair. The operation helped and everything has worked splendidly since then. During wondering process I also made suction hose straighter by boring it through the cabin support bar on the left.
Rigid support bar for cabin and steps. The bore for suction hose was made with hole saw with an eye not to weaken the strength.
Support bar's attachment points on both sides of the gearbox casting. The official mounting points for example for front loader frame are in the bottom of the casting under the clutch. I think points on the sides could be used on the same purpose.