L48 TLB boom sags when running.

[fried1765]

2006 L48 TLB (260 total hours) boom sags while operating only the loader.
Operating/traveling with RPM under 1,800 , must frequently reach back to raise sagging boom.
Is this likely a control valve issue, or a cylinder seal issue?
The WSM does not offer a suggestion for resolving this condition.

 

[TheOldHokie]

2006 L48 TLB (260 total hours) boom sags while operating only the loader.
Operating/traveling with RPM under 1,800 , must frequently reach back to raise sagging boom.
Is this likely a control valve issue, or a cylinder seal issue?
The WSM does not offer a suggestion for resolving this condition.

If the cylinder has to retract to sag it cannot leak internally.

If it extends when it sags it can.

The valve is always going to leak just a question of how fast. Spool leakage increases with hours and wear from dirty oil.

Dan

 

[fried1765]

If the cylinder has to retract to sag it cannot leak internally.

If it extends when it sags it can.

The valve is always going to leak just a question of how fast. Spool leakage increases with hours and wear from dirty oil.

Dan

Thanks.

The cylinder retracts fully, then slowly sags while the machine is running/moving/traveling.
Is there a fix?

New spool valve?
Only 260 total hours.
Hyd. oil & filter were changed at 200.

Bit of a nuisance to keep reaching back to raise sagging boom.

 

[Vlach7]

Had my bucket rams dropping with low hrs. rebuilding the rams was much cheaper than replacing the control valve and that fixed it. Good luck, and keep us updated.

 

[TheOldHokie]

The cylinder retracts fully, then slowly sags while the machine is running/moving/traveling.
Is there a fix?
Only 260 total hours.
Hyd. oil & filter were changed at 200.
Bit of a nuisance to keep reaching back to raise sagging boom.

There are fixes but first you need to figure out where the excessive leakage is.

Dan

 

[fried1765]

There are fixes but first you need to figure out where the excessive leakage is.

Dan

I have no idea how to do that.

 

[fried1765]

Had my bucket rams dropping with low hrs. rebuilding the rams was much cheaper than replacing the control valve and that fixed it. Good luck, and keep us updated.

Thank you.
Good to know!

 

[TheOldHokie]

Thank you.
Good to know!

I suspect that cylinder is tucked away but:

Pull the boom all the way back and chain it. Plug or cap the rod end at the hose or port. That will isolate it from the valve and hydraulically lock the cylinder.. If it sags the same after the chain is removed the cylinder is your problem . If it holds or sags a lot skower the valve is the issue.

Dan

 

[fried1765]

I suspect that cylinder is tucked away but:

Pull the boom all the way back and chain it. Plug or cap the rod end at the hose or port. That will isolate it from the valve and hydraulically lock the cylinder.. If it sags the same after the chain is removed the cylinder is your problem . If it holds or sags a lot skower the valve is the issue.

Dan

Yes,......the cylinder is nicely tucked in.
I will cap the hose that exits the rod end, as anything/everything else is inaccessible.

Your method of diagnosis does make sense.
Thank you!

MOD edit: You need to not type your responce inside the Quote.

 

[North Idaho Wolfman]

Simple answer, install the lock.
That what it's designed for!

 

[fried1765]

Simple answer, install the lock.

View attachment 104619

That is really not a very "simple" answer.
I was digging a long shallow ( 8") hole with the loader yesterday.
When the loader bucket was full, I then travelled 600', to a point where I then also needed the BH.
Fill loader bucket, pin backhoe, travel 600', unpin backhoe, use backhoe, repin backhoe, go back to beginning?
I only needed to raise hoe every third, or 4th trip, but still would be a PITA to pin every 4 trips.
VERY inconvenient

 

[TheOldHokie]

That is really not a very "simple" answer.
I was digging a long shallow ( 8") hole with the loader yesterday.
When the loader bucket was full, I then travelled 600', to a point where I then also needed the BH.
Fill loader bucket, pin backhoe, travel 600', unpin backhoe, use backhoe, repin backhoe, go back to beginning?
I only needed to raise hoe every third, or 4th trip, but still would be a PITA to pin every 4 trips.
VERY inconvenient

Not just inconvenient - the machine is broke.

The pin is for extended storage or long distance transport. The cylinder and valve are expected to hold during short distance transport operations. If they dont one or both is defective.

Dan

 

[North Idaho Wolfman]

That's it, tear it down, rebuild it as it's broken!

 

[mikester]

Simple answer, install the lock.
That what it's designed for!

View attachment 104619

You have to get off the machine to insert a boom locking pin? That's sucky considering to price of the machine...

 

[fried1765]

That's it, tear it down, rebuild it as it's broken!

There is no other solution to a sagging boom?

 

[fried1765]

You have to get off the machine to insert a boom locking pin? That's sucky considering to price of the machine...

I really don't think the boom lock pin was intended for short distance (a few hundred feet) travel use,...... but perhaps I am wrong.

 

[TheOldHokie]

There is no other solution to a sagging boom?

Hydraulic systems wear out and require repair. So far the problem description has been pretty subjective and you have not really quantified it. It would help if you timed the rate of drift so we can calculate the leakage rate. Based on that we can get a better idea of how normal/abnormal it is.

Raise the boom to full retract abd shut the machine off. Then meaure the rod extension that occurs over say 15 minutes. That will give us a real metric to evaluate.

If you repeat that measurement with the rod end hose capped we can also figure out how much of the leakage is coming from the valve.

Dan

 

[TheOldHokie]

I really don't think the boom lock pin was intended for short distance (a few hundred feet) travel use,...... but perhaps I am wrong.

You are not wrong.

Dan

 

[lynnmor]

I really don't think the boom lock pin was intended for short distance (a few hundred feet) travel use,...... but perhaps I am wrong.

I have the same issue with mine since new, once warmed up I can only go a short distance before the hoe is dragging on the ground. Two different dealers played with the cylinders but wouldn't touch the cheap, faulty valves. I am to just suck it up and live with it since the warranty is useless.

 

[BAP]

What you are experiencing is a very common problem among all backhoes of any brand. Usually, the cause is the seals in the cylinder are worn. I have fixed several over the years running John Deere and Case full size backhoes.