L3901DT Hydraulics Not Working

[JohnMackenzie]

So as the title says, my hydraulics on my L3901 aren't working at all, it's a DT so it's 4wd and manual, NOT hydrostatic. The tractor is only 3 years old with 430 Hrs on it so I'm not really sure why this problem came up. I have an LA525 FEL, BH77 backhoe, and two rear remotes, as far as I'm aware nothing has changed with anything, but it did sit not moving for a few months over the winter. So what's going on is the loader and backhoe will not move at all when I try any of the controls and my power steering isn't working either, All the quick connects are fully seated and connected properly so that isn't the issue. I called my local dealer and spoke to a mechanic over the phone before I decided to start tearing into it, and he said that it sounds like the hydraulic pump failed, I'm anal about all my servicing and maintenance so I've changed my hydraulic oil twice since I got it, and it is at the correct level for what that's worth. I suggested the PRV might be stuck open which he also said could be possible. I just came in from the shop after checking the PRV and taking a good look at the pump without actually taking it off the tractor (just looking in through disconnected lines) and nothing seems out of the ordinary. I just wanted someone else's opinion if this has happened to anyone of you before, and what was needed to fix it before I took the pump off to do a tear down and inspection. The mechanic said he thinks it might be covered under warranty but doesn't really know, on top of that I don't really want to have to take it in if I can fix it myself even though I'm well aware that would be the easiest, and I'm not paying $160/hr for a tech to come here just to diagnose the problem. Really just wondering if anyone else has anything to add to my list of troubleshooting tasks before I do anything unecessary. Thanks in advance ~ John

 

[TheOldHokie]

So as the title says, my hydraulics on my L3901 aren't working at all, it's a DT so it's 4wd and manual, NOT hydrostatic. The tractor is only 3 years old with 430 Hrs on it so I'm not really sure why this problem came up. I have an LA525 FEL, BH77 backhoe, and two rear remotes, as far as I'm aware nothing has changed with anything, but it did sit not moving for a few months over the winter. So what's going on is the loader and backhoe will not move at all when I try any of the controls and my power steering isn't working either, All the quick connects are fully seated and connected properly so that isn't the issue. I called my local dealer and spoke to a mechanic over the phone before I decided to start tearing into it, and he said that it sounds like the hydraulic pump failed, I'm anal about all my servicing and maintenance so I've changed my hydraulic oil twice since I got it, and it is at the correct level for what that's worth. I suggested the PRV might be stuck open which he also said could be possible. I just came in from the shop after checking the PRV and taking a good look at the pump without actually taking it off the tractor (just looking in through disconnected lines) and nothing seems out of the ordinary. I just wanted someone else's opinion if this has happened to anyone of you before, and what was needed to fix it before I took the pump off to do a tear down and inspection. The mechanic said he thinks it might be covered under warranty but doesn't really know, on top of that I don't really want to have to take it in if I can fix it myself even though I'm well aware that would be the easiest, and I'm not paying $160/hr for a tech to come here just to diagnose the problem. Really just wondering if anyone else has anything to add to my list of troubleshooting tasks before I do anything unecessary. Thanks in advance ~ John

You can certailnly find the problem yourself.

Unusual for a pump to fail out of the blue but the loss of PS is concerning. It is very simple to trouble shoot the pump on that tractor.

1. With the engine off disconnect the hydraulic supply line at the loader valve and put the open end in a clean bucket. This is the upper right hose on the hydraulic outlet block under the right floor board
2. Set throttle to idle and start the engine. You should IMMEDIATELY get a strong flow of oil out of the disconnected hose. IMMEDIATELY turn the engine off, DO NOT ALLOW IT TO RUN WITH THE HOSE DISCONNECTED

If you are getting oil the pump is working and we can move down the line looking for the problem

Dan

 

[Fedup]

I certainly wouldn't pull the pump and start tearing it apart just yet. It's not all that uncommon for a pump to lose prime sitting for months unused. I would first try loosening some lines on the pressure side of the pump and starting the engine for a few seconds to see what that gets you. If that doesn't help find a way to get some oil into the pump to wet the gears and try again.

I doubt you will get any warranty on a three year old pump.

 

[North Idaho Wolfman]

How long after it's last fluid and filter change was it parked?

And are you over freezing?

 

[TheOldHokie]

How long after it's last fluid and filter change was it parked?

And are you over freezing?

I just swapped a couple of those hoses today. You can have the hose off, pump tested, and hose reconnected in 5 minutes. All you neefd is a 7/8" open end wrench.

Dan

 

[JohnMackenzie]

To answer a few of your questions, fluid and filter were changed in June at 395 hrs. I did it twice at such low hours because the boot on the shifter had cracked and possibly let water in. No it isn't below freezing where I am, it was actually 18c (64f) yesterday. To Dan, I should've mentioned what I did for troubleshooting when I originally posted, I had cracked the line without taking it off all the way, it wasn't pouring out like was fully disconnected but it was moving fluid, its 10pm right now so I'll fully take it off and try that tomorrow. I hooked up a 3000psi gauge to the FEL connections, it wasn't registering pressure. The pump is moving fluid fairly well so I don't think it lost its prime, but it seems like there might be an internal leak because of the lack of pressure at this point. I'll screw around with it again tomorrow and see what I can do. Thanks for the advice so far, I'll let you fellas know what the problem was if I end up figuring it out. Cheers

 

[North Idaho Wolfman]

I've seen pumps that had a bad drive, and when there was no load they moved fluid, when loaded they didn't move anything.

 

[TheOldHokie]

To answer a few of your questions, fluid and filter were changed in June at 395 hrs. I did it twice at such low hours because the boot on the shifter had cracked and possibly let water in. No it isn't below freezing where I am, it was actually 18c (64f) yesterday. To Dan, I should've mentioned what I did for troubleshooting when I originally posted, I had cracked the line without taking it off all the way, it wasn't pouring out like was fully disconnected but it was moving fluid, its 10pm right now so I'll fully take it off and try that tomorrow. I hooked up a 3000psi gauge to the FEL connections, it wasn't registering pressure. The pump is moving fluid fairly well so I don't think it lost its prime, but it seems like there might be an internal leak because of the lack of pressure at this point. I'll screw around with it again tomorrow and see what I can do. Thanks for the advice so far, I'll let you fellas know what the problem was if I end up figuring it out. Cheers

Narrowing this down is not difficult.

Disconnect the upper right hose on the outlet block under the right floor board and connect the gauge to that outlet port. Start the tractor and you will be reading pump discharge pressure. Do not run the tractor more than 5-10 -seconds with that hookup - just long enough to get a pressure reading.

IIRC pump pressure should be 2400 PSI. If the pressure is not close to that value the problem is in the pump or the main system relief.

Whats bothering me is loss of PS. The pump has two sections. One supplies PS and the other supplies the implements. The pumps share a common suction side supply and engine drive shaft. I am not 100% clear on the pressure side but I think they are totally independent.

Dan

 

[TheOldHokie]

Here is a picture of the hydraulic outlet block on an L3901.

To test pump outlet pressure you can remove the hose connected to the port labeled Pump Outlet and connect your gauge directly to the port in the block. Alternatively you can follow that hose up to the loader valve, disconnect it there, and connect your gauge to the hose.

Once the gauge is connected start the engine and allow it to run just long enough to get a pressure reading. Do not allow the engine to run any longer than that. Disconnect the gauge and reconnect the hose.

Your pressure reading should be very close to 2400 PSI.

Clear as mud???

Dan

 

[JohnMackenzie]

Yeah 2400psi is what it should be, manual says 2349psi if you want to be pedantic. I've been screwing around with it since 11 this morning, and after doing everything suggested, I still have no pressure. The pump is still moving some fluid but still doesn't register on my gauge. I took off the pump supply hose from the lower tube to double check that pump hadn't lost its prime, from what I could tell that likely isn't the issue cause the metal tube was full and the hose had fluid in it. I also turned it upside down so I could put oil in it and crank the engine over and see it suck the oil into the pump, which it did. hooked everything up and fired up to bleed any air that might be in the system. Still no luck, but I let it idle for a few minutes, after probably 3 or 4 minutes it started making the noise like a hydrostatic tractor makes when you're going up a hill in high gear. I broke out the stethoscope and it sounds like its coming from the power steering side of it. I appreciate the help from you guys though, I'll still keep updating until I get the problem fixed. I should mention that I'm a millwright so its not like I'm just blindly doing stuff without any reason. Again Cheers

 

[North Idaho Wolfman]

Yeah 2400psi is what it should be, manual says 2349psi if you want to be pedantic. I've been screwing around with it since 11 this morning, and after doing everything suggested, I still have no pressure. The pump is still moving some fluid but still doesn't register on my gauge. I took off the pump supply hose from the lower tube to double check that pump hadn't lost its prime, from what I could tell that likely isn't the issue cause the metal tube was full and the hose had fluid in it. I also turned it upside down so I could put oil in it and crank the engine over and see it suck the oil into the pump, which it did. hooked everything up and fired up to bleed any air that might be in the system. Still no luck, but I let it idle for a few minutes, after probably 3 or 4 minutes it started making the noise like a hydrostatic tractor makes when you're going up a hill in high gear. I broke out the stethoscope and it sounds like its coming from the power steering side of it. I appreciate the help from you guys though, I'll still keep updating until I get the problem fixed. I should mention that I'm a millwright so its not like I'm just blindly doing stuff without any reason. Again Cheers

Pull the pump and drive and inspect

 

[TheOldHokie]

Yeah 2400psi is what it should be, manual says 2349psi if you want to be pedantic. I've been screwing around with it since 11 this morning, and after doing everything suggested, I still have no pressure. The pump is still moving some fluid but still doesn't register on my gauge. I took off the pump supply hose from the lower tube to double check that pump hadn't lost its prime, from what I could tell that likely isn't the issue cause the metal tube was full and the hose had fluid in it. I also turned it upside down so I could put oil in it and crank the engine over and see it suck the oil into the pump, which it did. hooked everything up and fired up to bleed any air that might be in the system. Still no luck, but I let it idle for a few minutes, after probably 3 or 4 minutes it started making the noise like a hydrostatic tractor makes when you're going up a hill in high gear. I broke out the stethoscope and it sounds like its coming from the power steering side of it. I appreciate the help from you guys though, I'll still keep updating until I get the problem fixed. I should mention that I'm a millwright so its not like I'm just blindly doing stuff without any reason. Again Cheers

I am with you - do not dissassemble things without a reason and good justification.

Just to help me understand please::

You removed the pump outlet hose shown in my picture and connected the 3000 PSI pressure gauge directly onto that port on the hydraulic block. No tees or any other connecton just gauge screwed into block.. Yes or No?

If yes you then started the tractor and the gauge showed what?

Dan

 

[JohnMackenzie]

Yes, so because of my job I have access to some specialized equipment, we have a hydraulic test kit which basically a calibrated digital gauge with an internal relief so you can put it inline with the system to not deadhead the pump, but still get an accurate pressure reading. I'm on a week off so I had to go in and get it yesterday, needless to say I had other plans for spending my vacation. Regardless it was jumping between 6 to 20 psi, so that's what I'm working with (couldn't tell you the pressure with the analog gauge).

 

[JohnMackenzie]

Also what I meant about the pump inlet hose was turn it so it looked like this

 

[TheOldHokie]

Yes, so because of my job I have access to some specialized equipment, we have a hydraulic test kit which basically a calibrated digital gauge with an internal relief so you can put it inline with the system to not deadhead the pump, but still get an accurate pressure reading. I'm on a week off so I had to go in and get it yesterday, needless to say I had other plans for spending my vacation. Regardless it was jumping between 6 to 20 psi, so that's what I'm working with (couldn't tell you the pressure with the analog gauge).

OK - just FYI you dont need or even want the relief in the instrument. There is one in the outlet block snd thats what you want to be testing along with the pump.

If no pressure and you know the pump is getting an inlet oil supply the main possibilities are defect in the pump or system relief jammed open. Given you also lost the PS circuit the relief seems unlikely.

Dan

 

[JohnMackenzie]

Pull the pump and drive and inspect

From what I'm dealing with so far I'm inclined to think what you said earlier about the drive might be likely, Ive seen it before on a hydraulic pallet lifter at one of the factories I work at, but that was a much smaller pump with an 1/8" tab that drove it. But like the mechanic said when I spoke to him on the phone, He's never seen something like this happen without there being an obvious problem like a major leak or pump making an awful noise, or hearing the relief valve open.

 

[JohnMackenzie]

OK - just FYI you dont need or even want the relief in the instrument. There is one in the outlet block snd thats what you want to be testing along with the pump.

If no pressure and you know the pump is getting an inlet oil supply the main possibilities are defect in the pump or system relief jammed open. Given you also lost the PS circuit the relief seems unlikely.

Dan

I'm not entirely sure how the test kit works, I just know how to use it, like I mentioned I borrowed it from work so its a professional unit that measures flow and pressure without interfering with the operation of whatever its connected to, its pretty neat actually. And yeah I'm thinking something less simple is the problem because of the loss of PS.

 

[TheOldHokie]

I'm not entirely sure how the test kit works, I just know how to use it, like I mentioned I borrowed it from work so its a professional unit that measures flow and pressure without interfering with the operation of whatever its connected to, its pretty neat actually. And yeah I'm thinking something less simple is the problem because of the loss of PS.

Personally I would spend some time looking at the hydraulic section of the WSM before jumping too far in. Here is the parts breakdown of the pump drive system. It looks like a splined shaft and gears - not something that would give up the ghost easily. I have not looked at my tractor to see how much stuff is layered over the pump. Hopefully its out in the open.

Dan

 

[North Idaho Wolfman]

Everything test wise that you said you have done points to a stripped spline or broken shaft on the pump.
I'm betting broken shaft, a broken shaft would not make any noise really.

 

[TheOldHokie]

Everything test wise that you said you have done points to a stripped spline or broken shaft on the pump.
I'm betting broken shaft, a broken shaft would not make any noise really.

These tractors are not very old. I own a 3 year old one and broken shafts on a hydraulic pump would not give me warm fuzzies. Have you ever seen this on an L01?

Dan