M59 hydraulics got slow and weak.

[Hersheyfarm]

Most equipment is like that, but as you dig you don't notice because you toggle the levers to work together. I think the dump takes fluid from lift on front end.

 

[5030]

I switched both my M9 and my 105 to Chevron Synthetic fluid at the first change and keep them on Chevron. It's not much cheaper than SUDT but it's not clear so you can see it and it seems to work well in heavy load situations. An added bonus is my hydraulic shuttle and loader operation is much smoother and wet clutch engagement is more progressive (than with SUDT).

The 9 and the 105 both take over 12 gallons each on a change.......

 

[Hersheyfarm]

I've put 60hr since the pumps were replaced. Still gets hot and seems weak. But this last time I was digging I shut the stall guard off and seemed better. My question is can the stall guard cause a flow restriction, and what about the hst response? I am going to keep both them off from now on. I've always kept the stall guard on.

 

[rScotty]

I've put 60hr since the pumps were replaced. Still gets hot and seems weak. But this last time I was digging I shut the stall guard off and seemed better. My question is can the stall guard cause a flow restriction, and what about the hst response? I am going to keep both them off from now on. I've always kept the stall guard on.

I wonder if it could be as simple as that? Frankly, I don't know about overheating - but that's not surprising as I dig at 50/60% of rated speed and normally work with the stall guard OFF. My reasoning being that I'm not in a hurry anyway, and the stall guard bothers me when it automatically revs the motor to a higher speed than it needs. If it would just pick up the revs enough to meet the load I'd probably leave it engaged. Along the same line, I'm now wondering if it makes any difference when digging if the HST control is in drive or neutral. Anyone know?
Have you thought about adding an oil cooler? I don't see how it could hurt.
rScotty

 

[Hersheyfarm]

I wonder if it could be as simple as that? Frankly, I don't know about overheating - but that's not surprising as I dig at 50/60% of rated speed and normally work with the stall guard OFF. My reasoning being that I'm not in a hurry anyway, and the stall guard bothers me when it automatically revs the motor to a higher speed than it needs. If it would just pick up the revs enough to meet the load I'd probably leave it engaged. Along the same line, I'm now wondering if it makes any difference when digging if the HST control is in drive or neutral. Anyone know?
Have you thought about adding an oil cooler? I don't see how it could hurt.
rScotty

Day before yesterday while I was digging an eleven ft deep sewer in gummy clay I tried all combinations. The stall guard doesn't have anything to do with throttle speed but it bypasses hydraulic pressure. Not sure how but would like to know. Must open a releif valve.

 

[J_J]

Reading through this thread, I see no mention of pressure readings.

Why not install a hyd pressure gage and observe the pressure while operating anything hyd. If you have two pump , put a QD on each circuit and monitor the pressure.

You need to know the pumps max pressure and set all the relief to the same relief setting of 50 to 100 psi below the pumps max pressure.

I believe when using a parallel valve, all spools have access to the fluid. If only one spool is operated, it can use full pump flow, but if another spool is also activated, the flow is split between the two spools. Less volume to each.

I think you need to investigate where the pressure is being lost.

With good pumps and good valves, the only remaining components is the cyl. If they are leaking, you should be able to isolate which cyl or cyl's.

If you look at the hyd gage while operating, you can see how much pressure the cyl is developing, and if it should get to the relief pressure, the relief will relieve.

Don't expect much pressure when just opening and closing the bucket, dipper,or boom. The only pressure you will see is the cyl's working to push or pull the weight of the metal in the BH.

You should only see relief pressure if working the BH real hard, or maxing out the cyl. You should also hear the relief sound.

There are test that either you or the tractor shop can do to trouble shoot the hyd system.

You might not have these, but a flow meter and pressure gage are some good things to have.

I don't know what stall guard is, but if you want max GPM's, the engine should be at max rpm.

 

[J_J]

I researched the stall guard that the Kubota uses, and to me , it is used for the hydrostatic transmission sys to prevent stalling when you are trying to overpower the hydro system by trying to do more work that designed into the machine.

With the stall guard on and the hydro transmission in neutral, does the engine change in rpm.

With stall guard off, the only load placed on the engine would be the gear pumps.

The engine should not stall because the relief valves will relieve the load. Most hyd pumps are selected to use a certain HP, and that is usually way below the HP of the tractor max HP.

If the engine does stall, then something in the hyd sys is not set right.

In neutral, the hyd pump is pumping, but at no or little pressure. The same with any control valve in neutral.

 

[Hersheyfarm]

From kubota:
Stall Guard is Kubota痴 trade mark for load sensing. Stall Guard is simply a result of the ECU sensing that engine RPM痴 are dropping. Then the ECU tells the variable displacement pump, to pump less oil to the drive motor so that the engine will not stall out. The benefit is that the ECU balances loads on the engine with transmission pump output to maintain peak efficiency and fuel economy of the tractor engine.

Now to me, no matter what hydraulic spool is open to cause the load on the motor the response of stall guard is to restrict fluid. To me tha generates heat. And can rob power by not letting the engine to lug at all.

 

[J_J]

I am thinking that is only works with the hydro transmission, like when you are traveling/moving the machine.

With the machine in neutral, which is where you should be , when using BH, the flow from the hydro pump is just flowing through the pump with no or very little resistance.

I don't think the gear pumps for the implements will cause the engine rpm's to vary to much.

 

[Hersheyfarm]

Just making sure. The m59 has a throttle response lever you can turn on and oFf that sences when you push the foot throttle, makes it like an automatic tranny, even works in N. The stall guard is something that manipulates hydraulic flow. It sences the engine rpm and hydraulic load and cuts hydraulic flow somehow. Not raising engine rpm's.