M4900 Hydraulic Problems. Power steering, PTO are OK. Everything else weak

[wheelinag]

My intelligent colleague just made a good point. Maybe there is some kind of suction problem? How much PSI does it take to make the steering work?

 

[TheOldHokie]

My intelligent colleague just made a good point. Maybe there is some kind of suction problem? How much PSI does it take to make the steering work?

I dont see this being a suction side problem and I don't like guess work when I can quantify things.

You now have a pump pressure test adapter - test the PS pump. PS pressure relief specification is 2631 PSI. Also measure the flow rate coming to the loader valve. All that takes is a bucket and a stop watch.

Dan

 

[wheelinag]

I dont see this being a suction side problem and I don't like guess work when I can quantify things.

You now have a pump pressure test adapter - test the PS pump. PS pressure relief specification is 2631 PSI. Also measure the flow rate coming to the loader valve. All that takes is a bucket and a stop watch.

Dan

I'll do this when I get the pump in as I'll be taking that off anyways.

While I haven't done any flow tests yet, I've discharged fluid into a bucket quickly a couple of times and did the pressure tests into a bucket as well. Probably 20 seconds total, but I'd say there's a little over a few gallons in there. Obviously not very scientific.

I need to put it on the back burner until the pump gets in and catch up on work.

 

[Russell King]

Just to provide you with more information on the tank return line since you asked a question that I didn’t see an answer to.

These Kubota tractors have open center hydraulic systems (for the most part). That means each valve just lets the hydraulic oil flow through with little pressure since there is no restriction to flow. The Power In port is the feed into the valve, a Power Beyond sleeve is added to one port that allows the open center flow to the next valve. Most valves in modern hydraulic systems have two lines that go to a double acting valve, pressure on one side forces the piston and ram to move. Tho other hose is used as a return line so the hydraulic fluid is fed back to the valve. Then the valve has a Tank Return port that dumps the fluid back to the tractor sump.

So most valves today on smaller Kubota tractors will have three lines (P, PB, T) connected to them. In older systems the valve may only use 2 lines and that can cause problems with too much pressure in the valve body (if I recall correctly).

 

[TheOldHokie]

Just to provide you with more information on the tank return line since you asked a question that I didn’t see an answer to.

These Kubota tractors have open center hydraulic systems (for the most part). That means each valve just lets the hydraulic oil flow through with little pressure since there is no restriction to flow. The Power In port is the feed into the valve, a Power Beyond sleeve is added to one port that allows the open center flow to the next valve. Most valves in modern hydraulic systems have two lines that go to a double acting valve, pressure on one side forces the piston and ram to move. Tho other hose is used as a return line so the hydraulic fluid is fed back to the valve. Then the valve has a Tank Return port that dumps the fluid back to the tractor sump.

So most valves today on smaller Kubota tractors will have three lines (P, PB, T) connected to them. In older systems the valve may only use 2 lines and that can cause problems with too much pressure in the valve body (if I recall correctly).

His valve has IN, PB, and TANK via the manifold.. Its the unused work port thats the issue.

Dan