Hydraulics help : no pressure high rpm - normal at idle

[trikepilot]

B2620 HST that has never given me any hint of trouble. Currently at 409hrs. At 400hrs I did the full required svc. This included full change of hydraulic oil and filters. I used SUDT2 and a Baldwin and a Donaldson filter. For the 8+ hours since the change, I have had zero issues.

Yesterday I went out to mow in 94deg weather with my finish mower. Before starting tractor, I checked all fluids due to recent maintenance and all were WNL. At end of almost 2hr mowing in high heat, neither the 3pt arms of the loader arms would move at high rpms. PTO and HST drive worked fine. If I brought engine RPMs to idle, the 2pt and loader arms would move but very slowly. Hydraulic hoses and fittings were VERY hot!

I brought tractor back to shed and shut it down. I did not have time to troubleshoot too much before I had to leave. Doing the online troubleshooting now. Postmortem as I left the farm... no visible leaks anywhere on or below tractor. After sitting for a few hours, hydraulic fluid dipstick indicted normal level and appearance of the newly changed SUDT2.

My online research reveals primary culprits as - clogged filters, faulty relief valve, air in lines, or failing pump. There seems to be a good bit of dogma for using OEM filters but I also see people saying they have had great results with Baldwin and Donaldson filters. I guess my first effort will be to drain SUDT2 into clean buckets and put in OEM hydraulic filters. Then make sure I bleed all the lines. I am also curious to see how it behaves when I am out there this coming weekend and start it up cold and run the loader and 3pt arms without doing anything else.

Any thoughts on other directions in which to head? The fact that this is all happening within 10hrs of a major fluid/filter change makes me feel that this is all self inflicted.

 

[TheOldHokie]

B2620 HST that has never given me any hint of trouble. Currently at 409hrs. At 400hrs I did the full required svc. This included full change of hydraulic oil and filters. I used SUDT2 and a Baldwin and a Donaldson filter. For the 8+ hours since the change, I have had zero issues.

Yesterday I went out to mow in 94deg weather with my finish mower. Before starting tractor, I checked all fluids due to recent maintenance and all were WNL. At end of almost 2hr mowing in high heat, neither the 3pt arms of the loader arms would move at high rpms. PTO and HST drive worked fine. If I brought engine RPMs to idle, the 2pt and loader arms would move but very slowly. Hydraulic hoses and fittings were VERY hot!

I brought tractor back to shed and shut it down. I did not have time to troubleshoot too much before I had to leave. Doing the online troubleshooting now. Postmortem as I left the farm... no visible leaks anywhere on or below tractor. After sitting for a few hours, hydraulic fluid dipstick indicted normal level and appearance of the newly changed SUDT2.

My online research reveals primary culprits as - clogged filters, faulty relief valve, air in lines, or failing pump. There seems to be a good bit of dogma for using OEM filters but I also see people saying they have had great results with Baldwin and Donaldson filters. I guess my first effort will be to drain SUDT2 into clean buckets and put in OEM hydraulic filters. Then make sure I bleed all the lines. I am also curious to see how it behaves when I am out there this coming weekend and start it up cold and run the loader and 3pt arms without doing anything else.

Any thoughts on other directions in which to head? The fact that this is all happening within 10hrs of a major fluid/filter change makes me feel that this is all self inflicted.

People always like to blame a recent service.

Check your backhoe couplers.

Dan

 

[trikepilot]

Dan - that's where I was able to determine that the hoses and fittings were HOT! This is where the backhoe supply (when no backhoe installed) goes back into the system to go to the 3pt lift which is the last "implement" in the loop as I understand it. Nothing appears to be amiss. What else should I check for when i am next out there? The FEL arms were not working either.

 

[TheOldHokie]

Dan - that's where I was able to determine that the hoses and fittings were HOT! This is where the backhoe supply (when no backhoe installed) goes back into the system to go to the 3pt lift which is the last "implement" in the loop as I understand it. Nothing appears to be amiss. What else should I check for when i am next out there? The FEL arms were not working either.

If the backhoe loopback is not fully connected you will get those exact symptoms. Specifically 3pt and boom cylinders on loader wont work but dump/curl will.

Dan

 

[trikepilot]

Dan

As usual... you are an wealth of info. As it turns out... my dump/curl works as normal. That'll be the first thing I check on Saturday

 

[trikepilot]

Well... no dice! Was out at farm yesterday briefly to drop off a new-to-me car hauler. So I checked the backhoe QD couplers and nothing looked abnormal. I disconnected and reconnected. I fired it up and ran it to operaring rpms. The front loader arms worked but sluggishly. The rear 3pt arms did nothing still.

I played around with various lever positions and rpms. I started to maybe confabulate sounds that were not typical? Maybe a slight whine that was not there. Who knows?

I lifted the loader arms and then the 3pt came up at a normal speed? WTF? I had accidentally left the 3pt lever in the up position and was able to duplicate several times the activation of the FEL lever initiating movement of the 3pt arms.

No fluid leakage anywhere on or below the tractor. Hydraulic fluid dipstick was WNL. Odd behavior indeed. I'll be able to dedicate more.energy to it this weekend. I am hopeful to diagnose and fix myself and avoid using my new trailer to take it to the dealer.

 

[TheOldHokie]

Well... no dice! Was out at farm yesterday briefly to drop off a new-to-me car hauler. So I checked the backhoe QD couplers and nothing looked abnormal. I disconnected and reconnected. I fired it up and ran it to operaring rpms. The front loader arms worked but sluggishly. The rear 3pt arms did nothing still.

I played around with various lever positions and rpms. I started to maybe confabulate sounds that were not typical? Maybe a slight whine that was not there. Who knows?

I lifted the loader arms and then the 3pt came up at a normal speed? WTF? I had accidentally left the 3pt lever in the up position and was able to duplicate several times the activation of the FEL


dan lever initiating movement of the 3pt arms.

No fluid leakage anywhere on or below the tractor. Hydraulic fluid dipstick was WNL. Odd behavior indeed. I'll be able to dedicate more.energy to it this weekend. I am hopeful to diagnose and fix myself and avoid using my new trailer to take it to the dealer.

Not so odd to me. The loader feeds the 3pt.

Your description is backwards of the usual problem. Lets sort that out piece by piece. Put the 3pt Iever full down and check loader operation.

Dan

 

[trikepilot]

Ok. Won't be out there till Friday afternoon sometime.

 

[TheOldHokie]

You

Ok. Won't be out there till Friday afternoon sometime.

Clearly have something happening in the neutral circuit. Any remotes or 3rd function?

Dan

 

[trikepilot]

I did add front and rear remotes about 3-4 months ago. However, the remote valve is plumbed such that when not in use, the entire remote system is NOT connected to the OEM circuit of hydraulics. It is totally isolated.

To make the remotes work, I have to disconnect the QDs on the backhoe supply/return loop and attach them to the supply/return lines on the remote valve block. I have not had the backhoe on in months.

Based on my understanding of remotes and how I plumbed them in I cannot see how this would cause the current issues. Plus I have had many hours of use since I did these remotes without these issues.

 

[TheOldHokie]

I did add front and rear remotes about 3-4 months ago. However, the remote valve is plumbed such that when not in use, the entire remote system is NOT connected to the OEM circuit of hydraulics. It is totally isolated.

To make the remotes work, I have to disconnect the QDs on the backhoe supply/return loop and attach them to the supply/return lines on the remote valve block. I have not had the backhoe on in months.

Based on my understanding of remotes and how I plumbed them in I cannot see how this would cause the current issues. Plus I have had many hours of use since I did these remotes without these issues.

Do you have the remotes hooked in? Knowing whats in the circuit or not is crucial. Merely messing with the QDs or a random failure can cause this sort of problem. Do you ubderstand why the loader and 3pt are related?

Dan

 

[trikepilot]

No. Hydraulics are as OEM. No remotes hooked up and have not been hooked up for some time.

Maybe I am not describing this well. Let me try again. My tractor has a backhoe that rarely gets used. There is a supply line from tractor that connects to backhoe and then a return from backhoe that connects to tractor. When backhoe is off tractor, these supply and return lines connect with M and F QDs. This is what I am currently running and have been for weeks.

If I need the remotes, I simply disconnect this "backhoe loop" at the QD and attach the supply and return lines to the appropriate connector on the remote valve block.

So in my mind... the tractor should be agnostic to the loop. In a normal setting, the fluid comes out the supply and immediately back into the return line. In a backhoe configuration, the fluid goes into the backhoe circuit and right back into the return line. And in the remotes configuration, the fluid comes out of supply line to the remote valve block and then back to the return line.

Again... for the last few months, I have had the first of the scenarios above as I have been primarily running the finish mower without a hydraulic top link.

Does this make sense?

 

[TheOldHokie]

No. Hydraulics are as OEM. No remotes hooked up and have not been hooked up for some time.

Maybe I am not describing this well. Let me try again. My tractor has a backhoe that rarely gets used. There is a supply line from tractor that connects to backhoe and then a return from backhoe that connects to tractor. When backhoe is off tractor, these supply and return lines connect with M and F QDs. This is what I am currently running and have been for weeks.

If I need the remotes, I simply disconnect this "backhoe loop" at the QD and attach the supply and return lines to the appropriate connector on the remote valve block.

So in my mind... the tractor should be agnostic to the loop. In a normal setting, the fluid comes out the supply and immediately back into the return line. In a backhoe configuration, the fluid goes into the backhoe circuit and right back into the return line. And in the remotes configuration, the fluid comes out of supply line to the remote valve block and then back to the return line.

Again... for the last few months, I have had the first of the scenarios above as I have been primarily running the finish mower without a hydraulic top link.

Does this make sense?

You are preaching to the choir. What you hsve is standard stuff and its broken. The way to fix it is finding the fault and that requires analyzing the circuit step by step.

One more time - do you understand the way the loader and 3pt interact on that circuit?

Dan

 

[trikepilot]

As i understand it, the fluid leaves the tractor reservoir via pump and goes to the loader block. Here it gets moved to the various functions of the loader (up/down/curl) as needed. There is also usually a PB port on this block where remotes can be tapped into. From this loader block, the fluid heads to the 3pt arms which are usually the last user of fluid before it returns to the reservoir to be circulated. However, in my case there is an option to interrupt this transit of fluid from the loader block to the 3pt and insert a backhoe (and in my case, the remote block). How the fluid is used for the HST while also going to the various implements, I have no clue.

 

[TheOldHokie]

As i understand it, the fluid leaves the tractor reservoir via pump and goes to the loader block. Here it gets moved to the various functions of the loader (up/down/curl) as needed. There is also usually a PB port on this block where remotes can be tapped into. From this loader block, the fluid heads to the 3pt arms which are usually the last user of fluid before it returns to the reservoir to be circulated. However, in my case there is an option to interrupt this transit of fluid from the loader block to the 3pt and insert a backhoe (and in my case, the remote block). How the fluid is used for the HST while also going to the various implements, I have no clue.

You have described the basic flow path but not the hydraulic interactions.

For example. what happens in that circuit when you raise the boom on the loader?

Dan

 

[trikepilot]

You have described the basic flow path but not the hydraulic interactions.

For example. what happens in that circuit when you raise the boom on the loader?

Dan

That level of granular understanding of the interactions within the circuit is not something I have much of.

 

[TheOldHokie]

That level of granular understanding of the interactions within the circuit is not something I have much of.

Right. And that ubderstanding is what you need to acquire if you want to analyse this behavior.

Operation

When you raise the loader inlet oil is sent to the base end of the cylinders. As the cylinders extend they displace oil in the rod end which is routed out the loader PB to the 3pt valve.

Why is that significant?

1. If the backhoe loopback is not connected the loader is hydraulucally blocked and neither loader or 3pt will work
2. If the 3pt valve is not in neutral snd the arms are down they will come up with the loader
3. If the 3pt valve is not in neutral and lift arms are all the way up the loader is hydraulically locked and will not raise.

Now using that information find your problem. Start at the head of the circuit with the 3ot full down and work backwards testing as you go.

Dan

 

[trikepilot]

Will do as soon as I get out there. Many thanks to your help here

 

[torch]

As i understand it, the fluid leaves the tractor reservoir via pump and goes to the loader block. Here it gets moved to the various functions of the loader (up/down/curl) as needed. There is also usually a PB port on this block where remotes can be tapped into.

If your loader has a PB port then that should be the one that goes back to the 3ph (and other functions). There should be a separate return line from the loader valve "Tank" port to the reservoir.

If that is the way it is piped, then an actuated relief valve in the FEL controls or actuation of the FEL controls will prevent pressure from building at the 3PH as the fluid will be returning direct to the reservoir via the "Tank" port. A stuck or actuated FEL relief would also prevent the lift arms from rising. The fact that it only happens at higher RPM might suggest a partial restriction (such as a partially engaged quick connect or a collapsed / kinked hydraulic line.

From this loader block, the fluid heads to the 3pt arms which are usually the last user of fluid before it returns to the reservoir to be circulated. However, in my case there is an option to interrupt this transit of fluid from the loader block to the 3pt and insert a backhoe (and in my case, the remote block).

Technically the backhoe should have a PB port to return fluid to the 3PH -- unless there is a diverter valve that selects between remote and 3ph functions. But it can work as you describe and the FEL relief will continue to protect the pump.

How the fluid is used for the HST while also going to the various implements, I have no clue.

Separate pumps and system. The only thing they share is the reservoir of fluid. The HST pumps are built into the transmission, the external hydraulics are powered via an externally mounted pump on the engine.

 

[TheOldHokie]

If your loader has a PB port then that should be the one that goes back to the 3ph (and other functions). There should be a separate return line from the loader valve "Tank" port to the reservoir.

If that is the way it is piped, then an actuated relief valve in the FEL controls or actuation of the FEL controls will prevent

pressure from building at the 3PH as the fluid will be returning direct to the reservoir via the "Tank" port.

He has a Kubota LA364 and Kubota loader valves have serial lift sections. When the boom is raised or lowered without operating the bucket spool the return oil goes to PB not tank. That puts the loader cylinders in series with the position control valve. A break or blockage in the PB circuit will stall the loader. Its a common problem typically caused by a bad BH coupler/connection or misadjusted 3pt feedback linkage. Based on the symptoms its probably whats happening here.

Dan