Problem with Lift Tilt Dump...

[SnowRidge]

It is when the jacks on the steering is fully extended on one side and the opposite side is fully retracted and you continue to try to cut it steeper that it affects the lift and dump. With the bucket loaded and you do this it may not completely stop it from raising but on mine you can tell definitely that it slows it down lifting a load, and if I remember correctly it completely stopped the lift a few times..........

Yes, but that's a relief valve opening because the steering rams are at their limits, not a priority valve diverting flow because the steering wheel is being turned, as I understand J_J's theory.

 

[catsco]

I was curious about your theory, J_J, so I experimented a bit with my PT-425 today. I was moving my 20 foot trailer around using a ball mount on QA adapter plate. I could not at any point disable the lift by turning the wheel. I was able to raise and lower the trailer tongue with the lift arms at will, all while steadily cranking the steering wheel either right or left.

The theory does not appear to hold up on the PT-425.

My PT-425 (2004, Kohler engine, fuel tank in steel lid) DOES disable steering/lift depending upon which is being used. While moving around, raising the bucket disables steering, and steering disables lift.

Lowering the bucket has no effect on steering, and steering has no effect on lowering the bucket.

Probably one of the many variations of PT design theory!

Regards,
Mark H.

 

[J_J]

talked to Terry. More than likely a bad relief valve. I have the pressure guage and will play with it, but it is either going to have to fail or get replaced by luck for me to really find the intermittent issue.

I pulled the relief valve but it has continued to act up so I think it is the valve itself.

I need some education on how a relief valve works. going to post that request in Hydraulics if anyone wants to weigh in...

Carl,

A relief valve is a simple device with a seat , a shaft that sits on the seat, and a spring, plus an adjusting nut. A strong spring holds the shaft on the seat until the pressure builds up enough to raise the plug and release the pressure. Some relief valves are fixed at a certain pressure, and others are adjustable. The set range may be as low as 500 psi to 3000 psi. The relief should be set to relieve the pressure below the maximum pressure of your hydraulic components.

 

[J_J]

I don't know what valve you have on your particular PT, but I think it is a safety thing to have a priority valve. It could be one of several valves, poppet valve, shuttle valve, slide valve. I do know that my lift operation stops when I turn. You can test this by putting a pressure gage at the input to the joystick valve. At the no turn position, you should have high pressure while trying to lift a heavy load. Now, while trying to lift, turn the steering wheel a little and check the pressure, and turn the steering to the limits, and check the pressure. You will have very little pressure unless you are doing work. If you are lifting a light load, you will have med pressure. You will see max pressure when lifting max load. Now if the gage were at the input to the steering circuit, and you turn the steering to the limit, the relief valve would operate, and show you the relief pressure. You would also be able to hear the relief valve bypassing.

An analogy might be electrical circuits, You can only guess what is happening in a circuit unless you put a meter in the circuit to give expected results, or not. If the test are not correct, you then start the process of trouble shooting, but you need that meter.

In general you have to know how the system works.

 

[J_J]

My PT-425 (2004, Kohler engine, fuel tank in steel lid) DOES disable steering/lift depending upon which is being used. While moving around, raising the bucket disables steering, and steering disables lift.

Lowering the bucket has no effect on steering, and steering has no effect on lowering the bucket.

Probably one of the many variations of PT design theory!

Regards,
Mark H.

Are you sure you disable steering while lifting? Doesn't sound logical. I believe steering always has priority,

What about raising a load while steering. You can always lower a load even with the pump off. In lowering, you are only opening a valve to release fluid back to tank.

 

[J_J]

Just to clear up what I said above. When lowering a load with pump running, the load is lowered by gravity, or a little pump pressure. If you continue to lower past the ground level, IE, raising the front wheels off the ground, then you are using high pressure to accomplish this.

 

[SnowRidge]

My PT-425 (2004, Kohler engine, fuel tank in steel lid) DOES disable steering/lift depending upon which is being used. While moving around, raising the bucket disables steering, and steering disables lift.

Lowering the bucket has no effect on steering, and steering has no effect on lowering the bucket.

Probably one of the many variations of PT design theory!

Regards,
Mark H.

Interesting. In well over four hundred hours of operation, I have never expererienced any interaction between lift/tilt and steering.

 

[woodlandfarms]

I really need a hydraulic schematic. My PT is so different than what you guys must have. these are moments when I want to ring Terry's neck.

Terry and I had a long talk. turns out that it is not the relief valve at the PTO block. The giveaway is that my brakes are working. We now suspect a blocked charging circuit. I have to pull it out, and put a guage on the whole system per JJ's recommendation. I will try to document my activities.

Apparently at the bottom of the charging block is a plug. Under the plug is another plug with a hole in it. This hole may be plugged up.

Carl

 

[MossRoad]

Linkage looks good. I mean I look under and things move like they are supposed to. And it is weird. It runs one moment then when I restart it is gone, then it starts. Problem is that there is NO hydraulic diagram for my particular PT. At least that I know of.

There are three pumps, wheels, pto, and steering lift. I have to double check but I think steering works when the lift does not... There is that charging circuit... Man. Call to Terry I guess. Nothing looks like it is leaking. I hit it with a hammer, nothing...

Darnit. My pickup blew up today. Not sure but I think I am cursed this weekend mechanically. Thank god our burn piles did not go out of control I guess...

Nice to see you are risking the Kubota's life by the fire and not your Power Trac's!

 

[MossRoad]

I was curious about your theory, J_J, so I experimented a bit with my PT-425 today. I was moving my 20 foot trailer around using a ball mount on QA adapter plate. I could not at any point disable the lift by turning the wheel. I was able to raise and lower the trailer tongue with the lift arms at will, all while steadily cranking the steering wheel either right or left.

The theory does not appear to hold up on the PT-425.

Our PT425 will sometimes not lift if I have the wheel all the way to one side. If I just let go of the wheel, it then lifts, but holding it to one side, it will not.