3pt leaks down fast, not cyl leak.

[FL_Jerry]

I have a ym2000 that started out with a weak 3pt. Somewhere along the troubleshooting path, which ended with me replacing the pump, my 3pt goes straight to the ground(fast) when I kill the engine. If the RPM's lower down, the 3pt starts to go down too.

When I close the lock valve the 3pt stays up with a load. Open the lock valve and down she goes. I thought I messed the 3pt control valve up inspecting and cleaning it so I just got a new one. Put it on and the same result.

The bypass valve is in the hydraulic cyl head, I checked it out. A 1/4 ball held in place with a plunger and spring.

I have a pressure guage T'd in right after the pump and when I pick the 3pt with a load, it goes to about 1kpsi and stays there. I didn't put the guage there until after I started having problems, so I don't know if this is normal.

I have a series setup(loader valve feeds 3pt), open center joy stick loader valve. I bypassed the loader and no difference.

Any ideas?

Thanks

Jerry

 

[Kernopelli]

I have a ym2000 that started out with a weak 3pt. Somewhere along the troubleshooting path, which ended with me replacing the pump, my 3pt goes straight to the ground(fast) when I kill the engine. If the RPM's lower down, the 3pt starts to go down too.

When I close the lock valve the 3pt stays up with a load. Open the lock valve and down she goes. I thought I messed the 3pt control valve up inspecting and cleaning it so I just got a new one. Put it on and the same result.

The bypass valve is in the hydraulic cyl head, I checked it out. A 1/4 ball held in place with a plunger and spring.

I have a pressure guage T'd in right after the pump and when I pick the 3pt with a load, it goes to about 1kpsi and stays there. I didn't put the guage there until after I started having problems, so I don't know if this is normal.

I have a series setup(loader valve feeds 3pt), open center joy stick loader valve. I bypassed the loader and no difference.

Any ideas?

Thanks

Jerry

ARRRGGGHHHHH! 3 PH problems...I just went down this road too. Two times I've had similar symptoms and with 2 different tractors. The first time it was junk in the control valve, second time was junk in the control valve but I took it , the relief valve and the speed control valve apart twice before I got it right.
To me it sounds like either a weak pump or your relief valve is staying partially open. I'm not too familiar with Yanmars system but I think some models have a lock valve under the seat, is this what you locked the 3 PH with?
The speed control on mine is set up like you describe your "bypass valve" ( I assume relief) is but it has a seperate relief valve too. Are you certain there isn't another valve in the system? Not saying your wrong here, just making suggestions. Do you have a service manual to help explain the entire system?

1000psi sounds like about 1/2 off what the pump should be making so that sounds problematic too. When you say "my 3pt goes straight to the ground(fast) when I kill the engine. If the RPM's lower down, the 3pt starts to go down too" I assume this is after replacing the pump? That sounds like either a weak pump or a partially open valve.

I have my loader/3PH plumbed the same way so I don't think that's an issue.

 

[FL_Jerry]

I can get 2200psi tilting the bucket one way or the other and holding the valve at it's limit. I think the 1000 or so if from the weight I have on the 3pt. If I chained the arms down, I think that would show my relief setting.

I'm thinking that the quick falling 3pt is robbing my pump power. Because the pump goes down so quickly and assuming the condition is the same when the engine is running, I think that part of the supplied fluid volume is being lost without generating lift. I would think that the pump is supplying enough volume to lift the load I have with the "loss".

If I can find why/where the fluid is bypassing the lift cyl. I think It will be licked so to speak.

This is a new pump, but with my old 3pt valve (maybe nothing to do with it), this pump blew out some internal O rings and shaft seal. I just replaced them all.

Everything I've read says the 3pt control valve, but this one is new. It has several ports on the bottom, one of which has an o-ring. That one goes to the hyd cyl. There is one almost directly under the input (top) and one where the return speed valve is. There is also a port toward where the spring mechanism sits and I assume this one vents pressure that gets back there to prevent hydrostatic lock.

Does your pressure stay up on your guage when you lift a load with the 3pt? I was thinking that pressure might only be there till the load was lifted to the desired setting... but I don't know.

Thanks for the suggestions... I'm tempted to take the new valve apart, but I'm worried I'd mess it up..

Jerry

 

[Farmerford]

I am not familiar with your tractor, but the linkeage for the three point hitch control valve may be out of adjustment. The linkeage is probably inside the rear housing, and causes the position of the three point hitch to follow the position of the control handle. Among other things, that linkeage (in most tractors) closes the valve to the TPH ram when the ram reaches the desired position. If your system maintains 1000psi whenever the TPH is activated, even after the ram lifts the arms fully, then your valve may not be closing fully, which could account for the continuous pressure (although it seems it would be full system pressure, unless the vavle leak were small, and the TPH ram had a small leak). The linkeage I am familiar with on older US tractors is fairly simple and robust, and rarely gives problems, but when you open the rear housing to clean the valve and bypass it is worth checking the linkeage carefully.

 

[Kernopelli]

I can get 2200psi tilting the bucket one way or the other and holding the valve at it's limit. I think the 1000 or so if from the weight I have on the 3pt. If I chained the arms down, I think that would show my relief setting.

I'm thinking that the quick falling 3pt is robbing my pump power. Because the pump goes down so quickly and assuming the condition is the same when the engine is running, I think that part of the supplied fluid volume is being lost without generating lift. I would think that the pump is supplying enough volume to lift the load I have with the "loss".

If I can find why/where the fluid is bypassing the lift cyl. I think It will be licked so to speak.

This is a new pump, but with my old 3pt valve (maybe nothing to do with it), this pump blew out some internal O rings and shaft seal. I just replaced them all.

Everything I've read says the 3pt control valve, but this one is new. It has several ports on the bottom, one of which has an o-ring. That one goes to the hyd cyl. There is one almost directly under the input (top) and one where the return speed valve is. There is also a port toward where the spring mechanism sits and I assume this one vents pressure that gets back there to prevent hydrostatic lock.

Does your pressure stay up on your guage when you lift a load with the 3pt? I was thinking that pressure might only be there till the load was lifted to the desired setting... but I don't know.

Thanks for the suggestions... I'm tempted to take the new valve apart, but I'm worried I'd mess it up..

Jerry

Well, I think you're right about the pump...not the problem. After your explanation I still stand by my original thought that there is a valve that is staying partially open and not allowing full pressure and fast bleed down at the 3 PH. As far as your question about pressure at my 3 PH...I don't have a dedicated gauge plumbed in so I am not sure. I tend to be with you on this though. Pressure should be highest when lifting heavy load s or when operation against a stop (i.e. at the point where the relief opens). I would assume that when a load is lifted and the valve is positioned to hold it in place that the oil then bypasses the 3PH valves "lift circuit" and becomes less pressurized....by how much I don't know though. I would think 1000psi would be high. Which also makes me think partially open valve and requiring the pump to supply constant pressurized flow in order to hold the loaded 3 point up.
I suggest using a service manual to reference and going through the system and any valve between the pump and reservoir gets checked out. My experience with disassembling valves is only work on one at a time and pay close attention to disassembly order and you should be fine. The valves may even have detailed diagrams in the manual to help disassemly/reassembly.