L48 TLB boom sags when running.

[fried1765]

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.

Thank you!
You have just convinced me that it is probably an issue not worth throwing money at.

 

[fried1765]

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

Thank you.
I will try timing the sag.
I actually think the sag is relatively slow while the machine is off, but may be faster while running.

For the hose end I must find a proper cap (JIC?), and I do not have a hydraulics shop anywhere nearby.

 

[TheOldHokie]

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.

Thank you.
I will try timing the sag.
I actually think the sag is relatively slow while the machine is off, but may be faster while running.

For the hose end I must find a proper cap (JIC?), and I do not have a hydraulics shop anywhere nearby.

I cant imagine why engine on or off would have any effect. The valve is in neutral and isolating/locking the cylinder.

Operating the tractor might generate some bouncing loads and pressure spikes that could increase leakage.

If you can measure leakage rate with the machine sitting still and cylinder both connected and isolated it will tell us a lot about whats happening in the circuit.

Dan

 

[fried1765]

I cant imagine why engine on or off would have any effect. The valve is in neutral and isolating/locking the cylinder.

Operating the tractor might generate some bouncing loads and pressure spikes that could increase leakage.

If you can measure leakage rate with the machine sitting still and cylinder both connected and isolated it will tell us a lot about whats happening in the circuit.

Dan

Thank you!
I shall do exactly that.......ASAP.

 

[lynnmor]

Thank you!
I shall do exactly that.......ASAP.

I disconnected all hoses to the backhoe and mine dropped just the same, that may be from the spools allowing flow to another cylinder???

 

[fried1765]

I disconnected all hoses to the backhoe and mine dropped just the same, that may be from the spools allowing flow to another cylinder???

Did you cap the ends of those hoses as being suggested by TheOldHokie ?

 

[lynnmor]

Did you cap the ends of those hoses as being suggested by TheOldHokie ?

No, but no fluid came out, maybe a good idea to keep air from going in.

 

[TheOldHokie]

No, but no fluid came out, maybe a good idea to keep air from going in.

He will be disconnecting exactly one and only hose and he should do all he can to make sure the hose remains as full of oil as possible. Getting some air in the circuit is almost inevitable but you can keep it to a minimum. Lift the hose up and pour oil in till it overflows before capping. Now when the boom is released its going to sag slightly as the trapped air is compressed. Thats the base point for measuring sag. Measure pin to pin. Wait 15 minutes and measure again. Subtract the two and you get rod extension. Compute the volume of oil lost from the rod end and divide by test time and you have leakage rate. Compare that to " normal" which for a bare cylinder should be damn near zero.

Dan

 

[fried1765]

He will be disconnecting exactly one and only hose and he should do all he can to make sure the hose remains as full of oil as possible. Getting some air in the circuit is almost inevitable but you can keep it to a minimum. Lift the hose up and pour oil in till it overflows before capping. Now when the boom is released its going to sag slightly as the trapped air is compressed. Thats the base point for measuring sag. Measure pin to pin. Wait 15 minutes and measure again. Subtract the two and you get rod extension. Compute the volume of oil lost from the rod end and divide by test time and you have leakage rate. Compare that to " normal" which for a bare cylinder should be damn near zero.

Dan

No way to test capped hose yet, but here are results from static sag test.
With cylinder extension at 2-3/8" (boom partially down), and waiting 15 min., sag went to 3-1/8", or 3/4" total sag.
With cylinder full retract (full up boom),, and waiting 15 min. sag was 1/2".
In both cases the 112 lb. root ripper was attached.
Seems like while traveling/bouncing, the sag might have been somewhat more.

Should I assume now that this may be quasi normal performance ????

 

[TheOldHokie]

No way to test capped hose yet, but here are results from static sag test.
With cylinder extension at 2-3/8" (boom partially down), and waiting 15 min., sag went to 3-1/8", or 3/4" total sag.
With cylinder full retract (full up boom),, and waiting 15 min. sag was 1/2".
In both cases the 112 lb. root ripper was attached.
Seems like while traveling/bouncing, the sag might have been somewhat more.

Should I assume now that this may be quasi normal performance ????

I would say very normal. Rough worst case calcs assuming a 2" cylinder, 1" sag, and using base end volume rather than rod end thats less than 5cc/minute.

Dan

 

[fried1765]

I would say very normal. Rough worst case calcs assuming a 2" cylinder, 1" sag, and using base end volume rather than rod end thats less than 5cc/minute.

Dan

Thank you for that information,
Very much appreciated.

 

[TheOldHokie]

Thank you for that information,
Very much appreciated.

You might want to retest that with a much heavier/overhanging load on the boom. The first test was at pretty low cylinder pressure and a higher pressure might show increased leakage. Would be an informative result.

Dan

 

[fried1765]

You might want to retest that with a much heavier/overhanging load on the boom. The first test was at pretty low cylinder pressure and a higher pressure might show increased leakage. Would be an informative result.

Dan

Thanks.
Will do!

 

[fried1765]

You might want to retest that with a much heavier/overhanging load on the boom. The first test was at pretty low cylinder pressure and a higher pressure might show increased leakage. Would be an informative result.

Dan

Here is more info on leak down/sag.

With boom full up, and 240 lb. 24" bucket, hanging from 112lb. ripper, total attached weight being 352 lb (+ unknown weight of thumb), the leak down measurement on the boom cylinder is 5/8" in 15 minutes.

Both this static test, and prior static test were done with hyd fluid temp at 70 deg F.
I would assume leak down to be somewhat faster with warm (or relatively hot) hyd. fluid.

I would also assume leak down to be somewhat faster with outstreached boom, though I would not travel like that.

 

[TheOldHokie]

Here is more info on leak down/sag.

With boom full up, and 240 lb. 24" bucket, hanging from 112lb. ripper, total attached weight being 352 lb (+ unknown weight of thumb), the leak down measurement on the boom cylinder is 5/8" in 15 minutes.

Both this static test, and prior static test were done with hyd fluid temp at 70 deg F.
I would assume leak down to be somewhat faster with warm (or relatively hot) hyd. fluid.

I would also assume leak down to be somewhat faster with outstreached boom, though I would not travel like that.

Yes to all of that. Let me explain my arithmetic.

I dont know the actual specifics but assume the boom has a 2.5" cylinder with a 1.25" rod. The cross sectional working area of the rod end is the area of the cylinder minus the area of the rod = 4.9 - 1.3 = 3.6 sq in.

So a 1" travel displaces 3.6 cubic inces of oil = 59 cc. Thats your base number.

Usung that base a 5/8" travel in 15 minutes displaces 39 cc total or 2.5cc per minute. That is pretty damn good considering 5cc per minute is average spool leakage just for the valve. I cant imagine that being a problem during operation Or anything that needs attention.

So go out and duplicate your usage and measure leakdown over 15 minutes in that situation. Is it similar or significantly greater than your static result?

Dan

 

[fried1765]

Yes to all of that. Let me explain my arithmetic.

I dont know the actual specifics but assume the boom has a 2.5" cylinder with a 1.25" rod. The cross sectional working area of the rod end is the area of the cylinder minus the area of the rod = 4.9 - 1.3 = 3.6 sq in.

So a 1" travel displaces 3.6 cubic inces of oil = 59 cc. Thats your base number.

Usung that base a 5/8" travel in 15 minutes displaces 39 cc total or 2.5cc per minute. That is pretty damn good considering 5cc per minute is average spool leakage just for the valve. I cant imagine that being a problem during operation Or anything that needs attention.

So go out and duplicate your usage and measure leakdown over 15 minutes in that situation. Is it similar or significantly greater than your static result?

Dan

Thank you.
My perceived leak down/sag issue was with warm fluid (loader use), but with only the 112 lb. ripper on the dipper stick.
May not be able to experiment with the issue again for a day or two.

 

[fried1765]

Yes to all of that. Let me explain my arithmetic.

I dont know the actual specifics but assume the boom has a 2.5" cylinder with a 1.25" rod. The cross sectional working area of the rod end is the area of the cylinder minus the area of the rod = 4.9 - 1.3 = 3.6 sq in.

So a 1" travel displaces 3.6 cubic inces of oil = 59 cc. Thats your base number.

Usung that base a 5/8" travel in 15 minutes displaces 39 cc total or 2.5cc per minute. That is pretty damn good considering 5cc per minute is average spool leakage just for the valve. I cant imagine that being a problem during operation Or anything that needs attention.

So go out and duplicate your usage and measure leakdown over 15 minutes in that situation. Is it similar or significantly greater than your static result?

Dan

With the machine having been run for 40 minutes today (oil warm):
Start of test..... boom cyl. 5/8" from full up.
After 15 minutes with same 352 lbs loaded as before, boom cylinder had leaked down to 2", from full up.
A 1-3/8" sag/drop in 15 minutes = 5-1/2" per hour?
This test was done with the dipper partially extended, and the 240 lb bucket chained to the 112 lb. ripper.
Might have not dropped quite as fast if the boom and dipper had both started from full up.
WADAYA think of the situation?

 

[TheOldHokie]

With the machine having been run for 40 minutes today (oil warm):
Start of test..... boom cyl. 5/8" from full up.
After 15 minutes with same 352 lbs loaded as before, boom cylinder had leaked down to 2", from full up.
A 1-3/8" sag/drop in 15 minutes = 5-1/2" per hour?
This test was done with the dipper partially extended, and the 240 lb bucket chained to the 112 lb. ripper.
Might have not dropped quite as fast if the boom and dipper had both started from full up.
WADAYA think of the situation?

I think you are getting 3X more leakage in the latest round of testsxwhich is getting close to "abnormal" . Sort of border line but I doubt there is much you could reasonably do to reduce the rate.i would not be rushing to tear things apart or throw money at it.

Dan

 

[Vlach7]

I think you are getting 3X more leakage in the latest round of testsxwhich is getting close to "abnormal" . Sort of border line but I doubt there is much you could reasonably do to reduce the rate.i would not be rushing to tear things apart or throw money at it.

Dan

Shucks, I thought that's why he came on the forum so we could help him throw his money at it.

 

[fried1765]

I think you are getting 3X more leakage in the latest round of testsxwhich is getting close to "abnormal" . Sort of border line but I doubt there is much you could reasonably do to reduce the rate.i would not be rushing to tear things apart or throw money at it.

Dan

Thank you!!

At 82, I REALLY do not want to "throw money at it".
I cringe a bit when any unexpected expense arises.
I am paying college expenses for a grandson, and that is like buying a new car every year.
I love my Kubota (and my Ford), but my grandson is on the dean's list, and I am lovin that a lot more!

When time permits I will try another warm oil test, with both boom and dipper starting in the full up position.