3PH Drooping

[Work Horse]

Afternoon Folks,

I'm working at addressing a few issues with my B7200HST tractor. My knowledge of hydraulics and tractor mechanics in general is limited, so I would greatly appreciate some guidance.

My main cause of concern at this point is my 3PH. It works, but only if I continue to bump up on the lever. If I set the lever somewhere in the middle of it's range the 3PH will lift up to the specified level, and begin to drop until it hits the ground - if I let it. Does this sound like an issue with the piston seal, or something within the lever mechanism itself?

Thank you all,

 

[TheOldHokie]

Put a couple hundred pounds on the lift, start tje ttactor, pull tje lever all tje way up and lock it in the offset at the top of the guide. Then shut the engine off and see how long the 3pt stays up.

Dan

 

[Work Horse]

Put a couple hundred pounds on the lift, start tje ttactor, pull tje lever all tje way up and lock it in the offset at the top of the guide. Then shut the engine off and see how long the 3pt stays up.

Dan

For the last year or so I've had a ballast box mounted to the 3PH. Not a ton of weight in it, mostly used to carry extra equipment around....

Done as instructed the 3PH ends up hitting the ground in less than a minute. Probably closer to 30 seconds if I got a more accurate time.

 

[TheOldHokie]

For the last year or so I've had a ballast box mounted to the 3PH. Not a ton of weight in it, mostly used to carry extra equipment around....

Done as instructed the 3PH ends up hitting the ground in less than a minute. Probably closer to 30 seconds if I got a more accurate time.

Soubds like the piston seal but latched like that it could be leaking back through the pump.

Try it agin but this time with the engine running and tje lever tied up just below the gate in the guide. You want to prevent the lever from drifting down.

Dan

 

[Work Horse]

Soubds like the piston seal but latched like that it could be leaking back through the pump.

Try it agin but this time with the engine running and tje lever tied up just below the gate in the guide. You want to prevent the lever from drifting down.

Dan

Hey Dan,

I posted a video on YouTube. It covers both test methods.

The hitch seems to hold if I keep the lever steady, but the entire time it holds the system groans/whines. Compared to other tractors I've seen that isn't normal, or maybe not as noticeable.

The system definitely bleeds down quickly.

 

[TheOldHokie]

Hey Dan,

I posted a video on YouTube. It covers both test methods.

The hitch seems to hold if I keep the lever steady, but the entire time it holds the system groans/whines. Compared to other tractors I've seen that isn't normal, or maybe not as noticeable.

The system definitely bleeds down quickly.

With the engine running it looks like the 3pt lever is oscillating. To me that indicates the position control feedback on the other side is sensing the leakdown and opening the valve to bring the arms back to the set height. Rinse and repeat. Do you understand what I am saying?

Dan

 

[Work Horse]

With the engine running it looks like the 3pt lever is oscillating. To me that indicates the position control feedback on the other side is sensing the leakdown and opening the valve to bring the arms back to the set height. Rinse and repeat. Do you understand what I am saying?

Dan

Kinda sorta....

The control lever doesn't "oscillate", it more so "drops down" a peg at at time. But I understand what you mean about the leakdown and the valve opening...

My question is, why? What is the "other side" you are referring to, something internally with the lever?

Also - when the hitch does hold (under constant tension on the lever) is the hydraulic whine normal?

 

[TheOldHokie]

Kinda sorta....

The control lever doesn't "oscillate", it more so "drops down" a peg at at time. But I understand what you mean about the leakdown and the valve opening...

My question is, why? What is the "other side" you are referring to, something internally with the lever?

Also - when the hitch does hold (under constant tension on the lever) is the hydraulic whine normal?

Your tractor has position control. When you pull the lever up it "sets" the desiref height of the lift.

On tje opposite side of the hydraulic cover you have a feedback rod that is connected to the lift arms. It senses the position of the arms.

Pulling the lever up opens the control vslve causing tjs lift arms to start up. When they reach the "set" height the feedback rod kicks the valve back to neutral and the arms are held in that position by the oil trapped in the lift circuit. At that point things are in equilibrium.

Now if the cylinder leaks a little oil the lift will "droop". The feedback rod senses that and "automagically" opens the valve to bring the lift back to the set point. As soon ss the set point is reached the feedback rod kicks the valve bsck into neutral.

Position control is constantly cycling the valve to compensated for "droop" allowing tje operator to do his thing. Clear as mud?

Dan

 

[Work Horse]

Your tractor has position control. When you pull the lever up it "sets" the desiref height of the lift.

On tje opposite side of the hydraulic cover you have a feedback rod that is connected to the lift arms. It senses the position of tjhe arms.

Pulling the lever up opens the control vslve causing tjs lift arms to start up. When they reach the "set" height the feedback rod kicks the vslve back to neutral and the srms are held in that position by the oil trspped in the lift circuit.

At that point things are in equilimrium. If the cylinder leaks a little oil the lift will "droop". The feedback rod senses that and "automagically" opens the valve to bring the lift back to the set point. As soon ss the set point is reached the feedback rod kicks the vslve bsck into neutral.

Clear as mud?

Dan

Clear as mud is a great way to describe it. Lol

So it seems likely cylinder seal(s) are leaking by... I'll have to take off the top cover to verify of thats the case.

Are there any adjustable points (other than the control valve) for the 3PH? At this point it definitely sounds like leak down...

 

[TheOldHokie]

Clear as mud is a great way to describe it. Lol

So it seems likely cylinder seal(s) are leaking by... I'll have to take off the top cover to verify of thats the case.

Are there any adjustable points (other than the control valve) for the 3PH? At this point it definitely sounds like leak down...

Yes it sounds like leakdown is the bsse problem but there is more going on as well.

I dont think you have to remove the cover to service the piston and oring. Not 100% sure but I think you can do that by removing the cap on the lift cylinder. I will have to look at the WSM to be sure. You definitly need to get a copy for yourself.

Dan

 

[Work Horse]

Yes it sounds like leakdown is the bsse problem but there is more going on as well.

I dont think you have to remove the cover to service the piston and oring. Not 100% sure but I think you can do that by removing the cap on the lift cylinder. I will have to look at the WSM to be sure. You definitly need to get a copy for yourself.

Dan

I actually re-downloaded the service and parts manuals earlier today.

I didn't have a chance to look to closely at them yet.

I appreciate your help Dan

 

[TheOldHokie]

I actually re-downloaded the service and parts manuals earlier today.

I didn't have a chance to look to closely at them yet.

I appreciate your help Dan

 

[Russell King]

Here is a link to a thread that shows the position control valve and the feedback linkage and how they work. It is pretty long and the first part is getting to the real issue. You could probably start on page 3 but would miss some diagrams.

L2350DT Hydraulic Problem 3-PT Shakes

Looking for some help... I have a L2350DT with a front loader. I installed the loader a couple of years ago. It is installed "in-line". My problem is with the 3 Point. When I lift an attachment it "shakes" or bounces. They only way to stop it other than lowering is to turn the Position Control...

www.orangetractortalks.com

There is also some discussion on the speed control valve and how it can be used to see if the cylinder or valve is leaking in post #60 and above for more troubleshooting you might be able to do.

 

[Work Horse]

Here is a link to a thread that shows the position control valve and the feedback linkage and how they work. It is pretty long and the first part is getting to the real issue. You could probably start on page 3 but would miss some diagrams.

L2350DT Hydraulic Problem 3-PT Shakes

Looking for some help... I have a L2350DT with a front loader. I installed the loader a couple of years ago. It is installed "in-line". My problem is with the 3 Point. When I lift an attachment it "shakes" or bounces. They only way to stop it other than lowering is to turn the Position Control...

www.orangetractortalks.com

There is also some discussion on the speed control valve and how it can be used to see if the cylinder or valve is leaking in post #60 and above for more troubleshooting you might be able to do.

Thanks a bunch man - I'll take a deep dive into this later today

 

[TheOldHokie]

Thanks a bunch man - I'll take a deep dive into this later today

Keep it simple. Put a new oring on the piston and proceed from there.

After you replace the oring I think you will find the position control lever is also loose and wont hold position. Thats why I had you tie it down for the engine running test. With it tied down the position control system did its job and the lift did not droop. I have one just like yours sitting here....

Dan

 

[Work Horse]

Keep it simple. Put a new oring on the piston and proceed from there.

After you replace the oring I think you will find the position control lever is also loose and wont hold position. Thats why I had you tie it down for the engine running test. With it tied down the position control system did its job and the lift did not droop. I have one just like yours sitting here....

Dan

Yea, I don't want to throw a ton of money at it for no good reason. I'm with you on starting simple....

Funny enough the fella in the link Russell King posted definitely has a loader from the same company I got one from. I did a write up on that a while back - wonder if he found the company through my thread... gonna keep reading...

 

[TheOldHokie]

Yea, I don't want to throw a ton of money at it for no good reason. I'm with you on starting simple....

Funny enough the fella in the link Russell King posted definitely has a loader from the same company I got one from. I did a write up on that a while back - wonder if he found the company through my thread... gonna keep reading...

We beat his problem to death in that thread and it wound up being internal to the valve. I dont see much in common with your symptoms. Lets see what doing the easy stuff yields.

The workshop manual describes the operation of the position control system in some detail. I think you will find that better reading than the old thread.

Dan

 

[Work Horse]

We beat his problem to death in that thread and it wound up being internal to the valve. I dont see much in common with your symptoms. Lets see what doing the easy stuff yields.

The workshop manual describes the operation of the position control system in some detail. I think you will find that better reading than the old thread.

Dan

From what I've seen so far I tend to agree. The issue with mine does seem different.

If you have any input off of what you saw in the WSM I'm all ears, you certainly seem to know your stuff when it comes to hydraulic systems.

 

[TheOldHokie]

From what I've seen so far I tend to agree. The issue with mine does seem different.

If you have any input off of what you saw in the WSM I'm all ears, you certainly seem to know your stuff when it comes to hydraulic systems.

My gut says the piston seal is leaking pretty badly. Thats problem #1.

Problem #2 is the position control lever/linkage has worn and lost the friction that normally holds it at a set position.

Combine the two and you get:

The piston leak causes the lift arms to droop, then the position control linkage reacts and kicks thst side of the valve linkage to rsise them, and that valve movement causes the position control lever to inch down lowering the set point.

The old Newtonian rule of every force has an equal and opposite force. Fix the oring to remove thst variable and we can see if Newton has a finger in the pie.

Dan

 

[Russell King]

From what I've seen so far I tend to agree. The issue with mine does seem different.

If you have any input off of what you saw in the WSM I'm all ears, you certainly seem to know your stuff when it comes to hydraulic systems.

I did NOT intend to imply that your problem was anything similar to the thread I linked to.

I just wanted you to get a good understanding of what the control position valve and feedback rod were doing.

Sorry if I gave you the incorrect impression.