L48 - Bucket boom loss of power

[TheAVguy]

Hi all, first time poster long time lurker!

I have an L48 and I’m experiencing a bit of a weird issue. I have several “data” points to mention, I don’t know if they’ll make sense, but the end all problem is that I don’t have full power on the bucket. After a while I can’t raise it at all, even at 2400RPM.
I flushed all the old hydraulic fluid and used UDT2. Old fluid was nasty, dirty and milky.
Replaced all the filters
Replaced all the hydraulic seals
Checked the relief valve on the front block, tightened it a little to increase pressure - no change.
New fuel filter - unrelated, but mentioning it.
Cleaned radiator and check anti freeze
Removed each line and flushed fluid to ensure nothing was stuck.

Observations:
Boom on the backhoe has lost almost all power, I haven’t replaced this seal yet. So I don’t know if it’s related.
At idle I cannot raise bucket nor backhoe boom
When I’m experiencing the slowdown and I curl the bucket down. The bucket doesn’t slam against the stops. This has made me believe there’s a problem with the return side of the lines.
If empty the bucket completely and rev it up to PTO indicator I can very slowly raise the bucket. I cycled it up and down several times and it does feel a little quicker on the way down after cycling it up and down. But it doesn’t speed up much and I still can’t pick anything up.
If I push the bucket down and curl down I am able to lift the front end of tractor.
I have plenty of pushing power. I just can’t lift anything.
Left right movement of the backhoe is very quick, compared to rest of hydraulics - I think this makes sense since it’s on the 3rd pump in the back.

What have I not done:
I haven’t removed the suction line filter, that’s on my list of things to try. Just don’t know if it’ll do anything.

I bought the service manual, which pointed me to the relief valve. But short of buying a new front pump, I don’t know what else to do!

 

[fried1765]

Hi all, first time poster long time lurker!

I have an L48 and I’m experiencing a bit of a weird issue. I have several “data” points to mention, I don’t know if they’ll make sense, but the end all problem is that I don’t have full power on the bucket. After a while I can’t raise it at all, even at 2400RPM.
I flushed all the old hydraulic fluid and used UDT2. Old fluid was nasty, dirty and milky.
Replaced all the filters
Replaced all the hydraulic seals
Checked the relief valve on the front block, tightened it a little to increase pressure - no change.
New fuel filter - unrelated, but mentioning it.
Cleaned radiator and check anti freeze
Removed each line and flushed fluid to ensure nothing was stuck.

Observations:
Boom on the backhoe has lost almost all power, I haven’t replaced this seal yet. So I don’t know if it’s related.
At idle I cannot raise bucket nor backhoe boom
When I’m experiencing the slowdown and I curl the bucket down. The bucket doesn’t slam against the stops. This has made me believe there’s a problem with the return side of the lines.
If empty the bucket completely and rev it up to PTO indicator I can very slowly raise the bucket. I cycled it up and down several times and it does feel a little quicker on the way down after cycling it up and down. But it doesn’t speed up much and I still can’t pick anything up.
If I push the bucket down and curl down I am able to lift the front end of tractor.
I have plenty of pushing power. I just can’t lift anything.
Left right movement of the backhoe is very quick, compared to rest of hydraulics - I think this makes sense since it’s on the 3rd pump in the back.

What have I not done:
I haven’t removed the suction line filter, that’s on my list of things to try. Just don’t know if it’ll do anything.

I bought the service manual, which pointed me to the relief valve. But short of buying a new front pump, I don’t know what else to do!

I shall be very interested in the resolution of this issue.
Have exact same machine, but luckily not the same problem....yet!

 

[TheOldHokie]

Hi all, first time poster long time lurker!

I have an L48 and I’m experiencing a bit of a weird issue. I have several “data” points to mention, I don’t know if they’ll make sense, but the end all problem is that I don’t have full power on the bucket. After a while I can’t raise it at all, even at 2400RPM.
I flushed all the old hydraulic fluid and used UDT2. Old fluid was nasty, dirty and milky.
Replaced all the filters
Replaced all the hydraulic seals
Checked the relief valve on the front block, tightened it a little to increase pressure - no change.
New fuel filter - unrelated, but mentioning it.
Cleaned radiator and check anti freeze
Removed each line and flushed fluid to ensure nothing was stuck.

Observations:
Boom on the backhoe has lost almost all power, I haven’t replaced this seal yet. So I don’t know if it’s related.
At idle I cannot raise bucket nor backhoe boom
When I’m experiencing the slowdown and I curl the bucket down. The bucket doesn’t slam against the stops. This has made me believe there’s a problem with the return side of the lines.
If empty the bucket completely and rev it up to PTO indicator I can very slowly raise the bucket. I cycled it up and down several times and it does feel a little quicker on the way down after cycling it up and down. But it doesn’t speed up much and I still can’t pick anything up.
If I push the bucket down and curl down I am able to lift the front end of tractor.
I have plenty of pushing power. I just can’t lift anything.
Left right movement of the backhoe is very quick, compared to rest of hydraulics - I think this makes sense since it’s on the 3rd pump in the back.

What have I not done:
I haven’t removed the suction line filter, that’s on my list of things to try. Just don’t know if it’ll do anything.

I bought the service manual, which pointed me to the relief valve. But short of buying a new front pump, I don’t know what else to do!

Have you looked at the port reliefs on that valve section? From the description you have lost power on one side of the cylinder so the port relief on that side is a prime suspect. Gunk in that dirty oil may have gotten lodged under the seat.

Dan

 

[TheAVguy]

Have you looked at the port reliefs on that valve section? From the description you have lost power on one side of the cylinder so the port relief on that side is a prime suspect. Gunk in that dirty oil may have gotten lodged under the seat.

Dan

So I took out the relief valve, but is the little nipple inside supposed to be in or out? In short, yes I looked at it, but I don’t necessarily know what I’m supposed to be looking for on it.

 

[TheOldHokie]

So I took out the relief valve, but is the little nipple inside supposed to be in or out? In short, yes I looked at it, but I don’t necessarily know what I’m supposed to be looking for on it.

Are we talking about the port relief for the boom spool on the backhoe valve? I dont know what they should look like when removed but you can test them easily enough. Disconnect the hose going to the boom cylinder and connect a pressure gauge to the work port. Operate the valve and read pressure. If it is not the same as system pressure the valve section is bypassing and most likely through that port relief.

Dan

 

[Smokeydog]

Don’t know how you missed the suction filter if you changed all the filters and oil.

Check any rubber connections on the suction side. Might only leak a little oil out but cracks let air in

Check the valves underneath the seat for correct configuration between backhoe and 3pt mode.

Check the quick disconnects from the backhoe to tractor to be clean and fully engaged. Break and reconnect to be sure.

Transmission and FEL working OK? Source of dirty oil? Neglect or missing cap?

 

[TheAVguy]

Dan,
Is this the relief valve you’re talking about? Just want to make sure we’re both talking about the same.

Smokey,
Yea I didn’t really know about that screen until recently. That’s the one that’s on the right side of the transmission case?
Regarding the levers and quick connects. Yes I did that. I also checked the valve at the front block. The FEL is also not working properly. Transmission is fine. Tractor has plenty of power. I don’t know the source of the dirty oil. I recently got this tractor with 1600 hrs on it and it was never really serviced.

 

[TheOldHokie]

Dan,
Is this the relief valve you’re talking about? Just want to make sure we’re both talking about the same. View attachment 104144

No - that is the main pressure for the tractor's front pump. If I understand your "data points" you have pump pressure except on the BH boom. That points to something in the backhoe circuit.

The backhoe valve has multiple port reliefs installed in it. They protect the work circuits from shock loads. The worksection for the boom has two - one on the extend outlet and another on the retract outlet. If they mslfunction that side of the cylinder will lose pressure. Consult the workshop manual for the backhoe.

As I said they are easy to check.

Dan

 

[TheOldHokie]

Dan,
Is this the relief valve you’re talking about? Just want to make sure we’re both talking about the same. View attachment 104144
Smokey,
Yea I didn’t really know about that screen until recently. That’s the one that’s on the right side of the transmission case?
Regarding the levers and quick connects. Yes I did that. I also checked the valve at the front block. The FEL is also not working properly. Transmission is fine. Tractor has plenty of power. I don’t know the source of the dirty oil. I recently got this tractor with 1600 hrs on it and it was never really serviced.
View attachment 104145

Another "data point" - the FEL is slso not working. That indicates a more general problem. What is the issue with it?

Dan

 

[BAP]

I would Not tear apart any relief valves and don’t know why anyone is even suggesting you tear apart any relief valves until you know for certain that your suction filter is clean and the lines are not leaking any fluid or air. If the pump can’t get oil properly, it’s not going to build pressure.

 

[TheOldHokie]

I would Not tear apart any relief valves and don’t know why anyone is even suggesting you tear apart any relief valves until you know for certain that your suction filter is clean and the lines are not leaking any fluid or air. If the pump can’t get oil properly, it’s not going to build pressure.

My focus on relief valves was based on his initial description of a boom specific problem not a general lack of hydraulic pressure.

"If I understand your "data points" you have pump pressure except on the BH boom."

If he has a general loss of function then of course the pump is the first place to look. Its complicated somewhat by the fact the machine has three pumps supplying different parts of the hydrauluc system. The BH valve is actually supplied by two different pumps.

And to be clear there is no need to "tear apart" any relief valves and I never suggested he should. You can diagnose them with a simple inline pressure test at the work ports on the backhoe valve.

I am a firm advocate of fault analysis followed by component isolation and and targeted testing. Its a process I have used with great success professionally for 50 years. To do that you need an accurate and complete description of the failure, a understanding of the hydraulic circuits involved, and a few simple test tools like a pressure gauge. That process will get to the source of the problem in the shortest time with the least dissassembly and at the least expense. A pressure test at the outlet from the hydraulic block is all thats needed to tell you if the pump is working or not. If you have pressure the entire pump side of the system includibg the suction lines gets a ckean bill of health - no disassembly required. Right now I am not clear on what is and isnt working and how.

Dan

 

[rbargeron]

Observations:
Boom on the backhoe has lost almost all power, I haven’t replaced this seal yet. So I don’t know if it’s related.
At idle I cannot raise bucket nor backhoe boom
When I’m experiencing the slowdown and I curl the bucket down. The bucket doesn’t slam against the stops. This has made me believe there’s a problem with the return side of the lines.
If empty the bucket completely and rev it up to PTO indicator I can very slowly raise the bucket. I cycled it up and down several times and it does feel a little quicker on the way down after cycling it up and down. But it doesn’t speed up much and I still can’t pick anything up.
If I push the bucket down and curl down I am able to lift the front end of tractor.
I have plenty of pushing power. I just can’t lift anything.
Left right movement of the backhoe is very quick, compared to rest of hydraulics - I think this makes sense since it’s on the 3rd pump in the back.

Since the OP's data points include general weakness in the front loader and the backhoe boom the main front pump's output flow seems the prime suspect. Its either being diverted somewhere or its low at the pump. Lifting the front of the tractor doesn't take much pressure with the backhoe's weight on the rear of the machine. The main pump is behind the steering pump up front.

 

[TheAVguy]

I'm going to order a pressure gauge so I can test what Dan is recommending, I see the point of the methodical approach.
The really weird this is that when the tractor is cold I seem to have more power, as the oil warms up this is what I end up with.
Video of loader failing to go up:

IMG_2164.MOV

drive.google.com

If you watch closely you should be able to see that releasing the curl down is also slow, but does go fast the second time around.

 

[TheOldHokie]

I'm going to order a pressure gauge so I can test what Dan is recommending, I see the point of the methodical approach.
The really weird this is that when the tractor is cold I seem to have more power, as the oil warms up this is what I end up with.
Video of loader failing to go up:

IMG_2164.MOV

drive.google.com

If you watch closely you should be able to see that releasing the curl down is also slow, but does go fast the second time around.

Couple possibilities why the loader wont raise and that should be the starting point. First test is pressure coming from the tractor. Just disconnect that hose and put your gauge on the tractor outlet. Start the tractor and read pressure then shut it down. I dont know the exact number but I would expect 2000 PSI plus. If you have that everthing up to the loader valve is fine and we move on to the loader valve. If low pressure we go the other way. We just keep working along the ciecuit until we find a problem.

Dan

 

[TheOldHokie]

I'm going to order a pressure gauge so I can test what Dan is recommending, I see the point of the methodical approach.
The really weird this is that when the tractor is cold I seem to have more power, as the oil warms up this is what I end up with.
Video of loader failing to go up:

IMG_2164.MOV

drive.google.com

If you watch closely you should be able to see that releasing the curl down is also slow, but does go fast the second time around.

Pressure testing will tell you a lot more than guessing from symptoms. Symptoms are for locatingvtest points.

Dan

 

[TheOldHokie]

Since the OP's data points include general weakness in the front loader and the backhoe boom the main front pump's output flow seems the prime suspect. Its either being diverted somewhere or its low at the pump. Lifting the front of the tractor doesn't take much pressure with the backhoe's weight on the rear of the machine. The main pump is behind the steering pump up front.

View attachment 104199

Understood. Do you know what backhoe functions are powered off the front pump versus the rear (not PS) pump?

Dan

 

[rbargeron]

Some of the L48s have a self-leveling valve for the front bucket - that has load-sensing and can be set for either open or closed-center operation. Does this machine have it? On my L48 it had been removed and the linkage from the bucket disconnected - WSM has no guidance on testing its operation but says it can affect proper loader operation. If it does they just recommend replacing it - mine has operated ok without it, but of course doesn't self-level.

 

[rbargeron]

Understood. Do you know what backhoe functions are powered off the front pump versus the rear (not PS) pump?

Dan

diagram from WSM :

 

[Smokeydog]

Is your new oil foamy? Indication of air being sucked in from line crack or filter gasket. Old filter gaskets come off? Sometimes the pipe nipple the filter screws on to can loosen from the filter housing. Operating steering wheel lock to lock is a way of bleeding air out of the system after oil/filter change.

7 years ago I took a chance on a M59 with 1050 hours that never had the hydraulic oil or filters changed. Engine oil had Napa filter and overall maintenance was questionable. Discounted value $10-15K off because of the maintenance issue. Has worked out to be a reliable machine. Regular maintenance and clean oil is required to keep these TLB happy.

 

[TheOldHokie]

diagram from WSM :

View attachment 104211

Thats helpful but a bit ambiguous. In the case of the backhoe dont both A ports go to back hoe valve?

Dan