Loader Getting Weak With Use?

[TheOldHokie]

Pump output.

I am seeing 1700 PSI.

Dan

 

[DustyRusty]

Can you take some reading with the loader off the tractor and using the rear port on the multi-gang hydraulic fitting? I would like to see how yours compares with mine and that is the port that I used.

 

[Soopitup]

Have you checked cycle times when hot yet? If not check them cold and then hot. Use a stop watch, time 3 cycles each function and direction and save the average. The specs are in the WSM. This will tell you if you have enough flow to the loader valve. You can bypass the BH valve to eliminate that , but I doubt that is the issue.

Remember you have a system that prioritizes a portion of flow to the steering valve. At idle where pump output is low you may not see enough flow to produce the results you are expecting.

I can't even lift the loader all the way up when it's hot. That was the original problem.
With the system only getting 600 PSI I can see why.

I just checked my 2019 BX23S with the loader and the backhoe off the tractor with the engine at normal operating temperature. At idle, (1200 RPM) I have 1500 PSI on a 3000 PSI oil-filled gauge. At loader/backhoe speed (2500 RPM) it jumps to 1650 PSI. At maximum throttle (3500 RPM) the reading goes to 1725 PSI. I have the shims to increase it and will probably do it sometime in the future but it isn't a high priority.

Thanks man, I appreciate you checking.
That sounds more like it.
I wouldn't be concerned if it was a little low at idle, but 600 PSI seems well below what it should put out.

 

[Soopitup]

I am seeing 1700 PSI.

Dan

At full throttle.
However I have 600 PSI at idle. That seems low to me.
And that was the original problem. When the tractor is hot I can't lift the loader at idle.

 

[Soopitup]

Can you take some reading with the loader off the tractor and using the rear port on the multi-gang hydraulic fitting? I would like to see how yours compares with mine and that is the port that I used.

It will probably take at least a few days, but I can do that.
I can't imagine the pressure will go up at that port though, the readings I just posted are basically right off the pump.

 

[TheOldHokie]

At full throttle.
However I have 600 PSI at idle. That seems low to me.
And that was the original problem. When the tractor is hot I can't lift the loader at idle.

It is low. In a desdhead condition you would normally see pretty much full pressure at all speeds like DustyRusty. i am struggling to come up with an explanation or fix.

Dan

 

[DustyRusty]

Take it back to the dealer and tell him you would like a new tractor. I have often wondered what Kubota does when a dealer can't fix a problem no matter how hard they try. Is it like a car where they buy it back from you and you can buy a new replacement?

 

[TheOldHokie]

At full throttle.
However I have 600 PSI at idle. That seems low to me.
And that was the original problem. When the tractor is hot I can't lift the loader at idle.

I went back to the WSM and did a little computation:

1. The pump is rated 6.2 GPM @ 3200 RPM. That works out to 2.9 GPM @ 1500 RPM
2. The PS priority flow divider sucks up 2.1 GPM @ 1500 RPM

So that is running on the ragged edge of having any excess (implement) flow at idle. If the priority flow goes a little high or pump output drops a little off theoretical there is nothing left for the implement circuit and you could possibly lose pressure due to the unavoidable slip (back flow) in a gear pump. That could possibly explain why pressure picks up at higher RPM - e.g. flow increases enough to offset the slip.

Dan

 

[TheOldHokie]

Take it back to the dealer and tell him you would like a new tractor. I have often wondered what Kubota does when a dealer can't fix a problem no matter how hard they try. Is it like a car where they buy it back from you and you can buy a new replacement?

Not a snoqball's chance......

Dan

 

[hagrid]

Not a snoqball's chance......

Dan

Picture/image of snoqball, plz.

 

[TheOldHokie]

Picture/image of snoqball, plz.

 

[Soopitup]

I went back to the WSM and did a little computation:

1. The pump is rated 6.2 GPM @ 3200 RPM. That works out to 2.9 GPM @ 1500 RPM
2. The PS priority flow divider sucks up 2.1 GPM @ 1500 RPM

So that is running on the ragged edge of having any excess (implement) flow at idle. If the priority flow goes a little high or pump output drops a little off theoretical there is nothing left for the implement circuit and you could possibly lose pressure due to the unavoidable slip (back flow) in a gear pump. That could possibly explain why pressure picks up at higher RPM - e.g. flow increases enough to offset the slip.

Dan

Alright, thanks.
I don't know how well I can trust the dealer to get this troubleshot in a timely manner.
Or to competently troubleshoot it (I bought a chainsaw from them a few years ago that still doesn't run right, they've had it multiple times)
Not to mention I don't have a trailer at the moment to bring it, I'll have to hire a tow truck.

I may pick up a flow meter to confirm. I'd rather have everything lined up before I approach the dealer.
I wonder how expensive one will be that can accurately measure that low.
I'm definitely not keen on them tearing apart my transmission.

Take it back to the dealer and tell him you would like a new tractor. I have often wondered what Kubota does when a dealer can't fix a problem no matter how hard they try. Is it like a car where they buy it back from you and you can buy a new replacement?

Yeah, I doubt that will happen unfortunately.

 

[whitetiger]

I'm definitely not keen on them tearing apart my transmission

The hydraulic pump is not in the transmission, it is mounted right above the LH rear axle housing.

 

[TheOldHokie]

Alright, thanks.
I don't know how well I can trust the dealer to get this troubleshot in a timely manner.
Or to competently troubleshoot it (I bought a chainsaw from them a few years ago that still doesn't run right, they've had it multiple times)
Not to mention I don't have a trailer at the moment to bring it, I'll have to hire a tow truck.

I may pick up a flow meter to confirm. I'd rather have everything lined up before I approach the dealer.
I wonder how expensive one will be that can accurately measure that low.
I'm definitely not keen on them tearing apart my transmission.



Yeah, I doubt 8that will happen unfortunately.

I dont think you are going to get much sympathy from the dealer for your low implement pressure numbers at idle RPM. Thats a split flow parallel circuit with priority to the PS side. Kubota specifies implement side (excess flow) pressure at WOT not idle speed.

Your implement pressure at max engine speed is 1700 PSI and all it may take is a tweak of the relief valve adjustment to get it up to the WSM specification.

Dank

 

[Soopitup]

The hydraulic pump is not in the transmission, it is mounted right above the LH rear axle housing.

Ok, thanks.
I haven't had a chance to look at exactly what it takes to tear into it yet.
What I should have said is I'm not keen on the dealer tearing into my tractor.
There are good techs and not so good techs and I don't know which I'll get.

I dont think you are going to get much sympathy from the dealer for your low implement pressure numbers at idle RPM. Thats a split flow parallel circuit with priority to the PS side design. Kubota specifies implement side (excess flow) pressure at WOT not idle speed.

Your implement pressure at max engine speed is 1700 PSI and all it may take is a tweak of the relief valve adjustment to get it up to the WSM specification.

Dan

Yes, I noticed that. That's my feeling too and another reason I'm not in a rush to take it to them.

That's actually my next step. I want to look in there anyways, make sure nothing is stuck in there (like little gobs of silicone). Not likely but it's an easy check. I figured I would bump the pressure some while I was in there.

I do want to know what the pump is flowing, for my curiosity and peace of mind. At some point I'll get to that.

When I was at the dealer last fall a couple of techs were in the parts dept and I mentioned this problem. They agreed it didn't sound right.
Depending what I find, if I find anything, and how much work/money it is I may bring it to them at some point.

 

[TheOldHokie]

Ok, thanks.
I haven't had a chance to look at exactly what it takes to tear into it yet.
What I should have said is I'm not keen on the dealer tearing into my tractor.
There are good techs and not so good techs and I don't know which I'll get.


Yes, I noticed that. That's my feeling too and another reason I'm not in a rush to take it to them.

That's actually my next step. I want to look in there anyways, make sure nothing is stuck in there (like little gobs of silicone). Not likely but it's an easy check. I figured I would bump the pressure some while I was in there.

I do want to know what the pump is flowing, for my curiosity and peace of mind. At some point I'll get to that.

When I was at the dealer last fall a couple of techs were in the parts dept and I mentioned this problem. They agreed it didn't sound right.
Depending what I find, if I find anything, and how much work/money it is I may bring it to them at some point.

The workshop manual has detailed diagnostic prodedures for measuring pump flow, pump outlet pressure, relief vslve cracking pressure, and flow divider priority flow rate. You will need one of these and a flow control (loading) needle valve to add to your test gear:

H600A-010 : Hedland 3500psi Aluminum Flow Meter for Petroleum Fluid, #10 SAE (5/8), 1 to 10 GPM

As the leading manufacturer of hydraulic and pneumatic flow measurement solutions, the Hedland product line features over 15,000 inline variable area flow meters (rotameters) to measure petroleum type fluids, water-based fluids, water, phosphate esters, pressurized air and other compressed...

www.onehydraulics.com

Based on the numbers you have reported so far that may be educational but its not likely to show any actual system problem.

Bottom line is the loader and backhoe suck hind teat on the priority flow divider. At idle speed there is not enough flow to satisfy much more than the PS which is sucking on the front teat.

NOTE: Colorful language used for the entertainment of @hagrid The Lurker

Dan

 

[D2Cat]

The workshop manual has detailed diagnostic prodedures for measuring pump flow, pump outlet pressure, relief vslve cracking pressure, and flow divider priority flow rate. You will need one of these and a flow control (loading) needle valve to add to your test gear:

H600A-010 : Hedland 3500psi Aluminum Flow Meter for Petroleum Fluid, #10 SAE (5/8), 1 to 10 GPM

As the leading manufacturer of hydraulic and pneumatic flow measurement solutions, the Hedland product line features over 15,000 inline variable area flow meters (rotameters) to measure petroleum type fluids, water-based fluids, water, phosphate esters, pressurized air and other compressed...

www.onehydraulics.com

Based on the numbers you have reported so far that may be educational but its not likely to show any actual system problem.

Bottom line is the loader and backhoe suck hind teat on the priority flow divider. At idle speed there is not enough flow to satisfy much more than the PS which is sucking on the front teat.

NOTE: Colorful language used for the entertainment of @hagrid The Lurker

Dan

If HE is a lurker he's a good, consistent one. He has well over 800 post and been at it over 6 years! I appreciate his post, they often make someone think more clearly with some humor.

 

[hagrid]

The use of mammary gland positions to illustrate flow priority is insightful and well received.

My countenance beams down upon this thread with pride and satisfaction.

 

[North Idaho Wolfman]

I actually opened this thread specifically because I had seen Hagrid had posted, I always love his wit!

 

[TheOldHokie]

I actually opened this thread specifically because I had seen Hagrid had posted, I always love his wit!

He is in mid-season form and you just got your money's worth !!!

Dan