HST Odd Behavior

[aerolland]

Greetings all! I've got a 2001 B2150 HST with a little north of 3K hours on it (was an old state owned unit) that I have split, thrown some new parts around, and repainted to like new - all while hoping the HST was solid...

For the most part it is. Definitely has some noticeable power loss, but is decent enough to last a while longer before it get's a new HST. The odd part goes like this, let me set the scene:

Scene 1)
You're dragging a box blade engaged well in the soil and the tires loose traction, so you want to lift the rear 3pt arms a bit to reduce the bite, this triggers the HST problem

Scene 2)
You're using the front loader to dig into a pile of hard clay soil, while you are rocking the bucket back and forth to get the teeth chewing, the dump function triggers the HST problem


In both scenarios above, the HST will act like it's starving for fluid. It makes an audible frequency change as if you are pushing against something non-movable. This will continue until you lessen your demand on the HST peddle and as soon as it goes away you can go back to 100% peddle.

Fluid is clean and beautiful. Fluid is 100% volume, if not slightly over filled. Filter is new from when tractor was reassembled, roughly 6-8hrs ago. All hydraulic functions work as expected.


Could the loader spool valve be worn to the point that it's causing problems? I plan to replace it, just ordered more fittings to make it work actually. 3 pt arm control going bad?

One note, it was attempted to shim the pressure relief valve to increase system pressure but could only get ~2,100 psi out of the charge pump. Thinking it's probably time to rebuild/replace it - but could that be an issue?

Although I have not pulled pressures at various locations, I'm stumped at this point...

Thanks!

 

[helomech]

Sounds kind of normal to me. What gear are you in. The engine will only deliver so much power to the pump, and the pump will only deliver so much fluid. If you go above these you will lose power somewhere. I run into this all the time with my 5100. Either select a lower gear, or don't dig as deep.

The harder you push the peddle the less power you will have. This is the most common issue I see with people using HST. They push the peddle all the way down when power is needed. That is 100% the wrong thing to do.

 

[North Idaho Wolfman]

First, Sorry to say it but your misinformed as to the year of the unit, they stopped producing the b2150 back in 1996, so the unit is anywhere from 1988 to 1996.

Secondly if your getting 2100PSI your over what the system wants to see, spec is 1920PSI.
Don't keep raising it as it will just do damage.

Have you confirmed that your HST loss is not actually caused by a slipping Clutch disk?

 

[100 td]

Just trying to get my head around this, please add further explanation for dummies like me

You're dragging a box blade engaged well in the soil and the tires loose traction, so you want to lift the rear 3pt arms a bit to reduce the bite, this triggers the HST problem

Scene 2)
You're using the front loader to dig into a pile of hard clay soil, while you are rocking the bucket back and forth to get the teeth chewing, the dump function triggers the HST problem

In both scenarios above, the HST will act like it's starving for fluid. It makes an audible frequency change as if you are pushing against something non-movable. This will continue until you lessen your demand on the HST peddle and as soon as it goes away you can go back to 100% peddle.
Filter is new from when tractor was reassembled, roughly 6-8hrs ago. All hydraulic functions work as expected.
One note, it was attempted to shim the pressure relief valve to increase system pressure but could only get ~2,100 psi out of the charge pump.

<the tires loose traction,>
So your HST is spinning/driving your wheels, you lift your 3pt and the HST acts like it's starving for fluid? Does it keep spinning the wheels?
What gear are you in?
<the dump function>
So you are dumping your bucket while in a pile, raising the front of the tractor, while trying to push into the pile at the same time and the HST acts like it's starving for fluid? Are the wheels spinning/driving at this time?
What gear are you in?
<when tractor was reassembled,>
What was the fault/reason the tractor was disassembled, what was found/changed/repaired/adjusted while apart?
<out of the charge pump>
I'm guessing you are actually talking about the hydraulic pump relief valve on the hydraulic block?
Have you been into the HST and adjusted the charge relief valve or done anything to the HST?

 

[aerolland]

First, Sorry to say it but your misinformed as to the year of the unit, they stopped producing the b2150 back in 1996, so the unit is anywhere from 1988 to 1996.

Secondly if your getting 2100PSI your over what the system wants to see, spec is 1920PSI.
Don't keep raising it as it will just do damage.

Have you confirmed that your HST loss is not actually caused by a slipping Clutch disk?

Good point, I think I knew that though not sure why I thought so recent. I seem to remember doing the hourly math in my head for a ~20 year old tractor when I made the purchase 2 years ago... Oopsie! Thank's for calling me out, can always count on the experts!

 

[aerolland]

This man is on point! Let me add comments in another color maybe...

Just trying to get my head around this, please add further explanation for dummies like me

<the tires loose traction,>
So your HST is spinning/driving your wheels, you lift your 3pt and the HST acts like it's starving for fluid? Does it keep spinning the wheels?
What gear are you in?
< Low range, 4WD, with minimal peddle travel (going for max torque to wheels, not speed). It does not continue to spin the wheels, but rather acts like you are pushing against something solid with MEGA traction. >



<the dump function>
So you are dumping your bucket while in a pile, raising the front of the tractor, while trying to push into the pile at the same time and the HST acts like it's starving for fluid? Are the wheels spinning/driving at this time?
What gear are you in?
< Any range of transmission, MED usually. LOW range will get you more digging force obviously but behavior is the same regardless of transmission selection. Wheels do not have to be spinning, can be creeping forward. I can replicate this behavior if I am say spreading gravel while moving (forward OR backward). It's the act of dumping the bucket that seems to trigger the tranny behavior. Not sure if lowing the bucket does the same, I will have to try that tonight. Rolling the bucket back or lifting the bucket do not seem to trigger the tranny. >

<when tractor was reassembled,>
What was the fault/reason the tractor was disassembled, what was found/changed/repaired/adjusted while apart?
< The tractor was bought "as-is" and was using the backhoe when the center of the clutch hub failed. The previous owner couldn't stomach the $4K bill estimated to split and repair so he traded in on newer unit. I replaced the clutch, throw out bearing, input shaft, u-joints in between clutch and tranny, and a couple of seals. >

<out of the charge pump>
I'm guessing you are actually talking about the hydraulic pump relief valve on the hydraulic block?
< Correct, the one by your right foot. Distribution block to power steering and loader. >


Have you been into the HST and adjusted the charge relief valve or done anything to the HST?
< No I have not done anything to the back half of the tractor when I separated it for the clutch work.

>

 

[aerolland]

This man is on point! Let me add comments in another color maybe...



>

Tested tonight. Odd thing was it didn't seem to respond the same until the temperature came up and once I really started pushing it. Had to really dig in clay with loader to replicate, box blade was easier to replicate.

Tried to take a video of it, see link below. Box engaged enough to get all 4 wheels spinning, then raised the box. You can see the wheels stop spinning and hear the hydro. I don't change the peddle position at all.

https://youtu.be/NSgHuFQgRMs

One note, when using the tractor for extended periods of time, the steel hydraulic lines are very hot to the touch, almost can't keep your hand on them. Lines like the ones coming off the distribution manifold by your right foot. Normal?

Sent from my SM-G955U using Tapatalk

 

[100 td]

I wrote this before your video you just posted, some may/may not still be valid, I'll have to look/listen to your video later, others may sort this for you.

Firstly, North Idaho Wolfman, whitetiger and others are far more qualified than I to comment on this.
Unfortunately I don't have time to address your responses today, as there is plenty to additionally comment on, but I'll quickly add the following, which hopefully add to info you have already provided for others to comment on -

It appears you a starting with a 3000 hour/ ~20 year old non functioning unit and you do not have any real service history of the machine, so there might be an underlying problem which was there before you got the tractor, or it has manifested since you acquired it. This makes fault finding from afar by anyone, a whole lot more difficult.

The age/hours also means orings at critical junctions (on suction lines especially) could be deteriorated, connections on flexible junctions on oil pipes and oil coolers could also be compromised which could cause problems. Splitting a tractor may have affected any of these as well.
While a small increase in system hydraulic pressure would not generally affect things, for a start, reset the main relief back to factory specifications. Then those who are here trying to assist you fault find are working to standards, not something with the timing advanced, the ECU chipped and the boost over compensated! If and when your problem is resolved, you can go and play then.

Get your parts/service manual out and go over all connections
What oil brand and grade did you refill with?
Did you use the correct Kubota branded filter? (please check it's the correct part no. for your machine)
Have you cleaned the hydraulic screen and was there any debris present?
Did you replace the orings? Please check all flexible joints and clamps.
Did you cut open or notice any debris in the old HST filter?
Are you certain the HST filter is fitted correctly/square/seal intact/not double seal etc?

Do you have a service manual for the tractor?
If you do, it may be worth posting a pic of the hydraulic flow circuit.
It may not be fixed overnight, but if we keep nibbling away at it and get more info, perhaps we or someone else will get some traction on sorting it out.
YMMV

 

[chim]

In the video it looks like raising the box blade (maybe adding to the load by ripping it up through the dirt?) uses enough of the hydraulic output to reduce the flow to the trans.

With regard to the hot fluid, the B7500 I had would sometimes develop a strange steering feel when going through tall heavy grass. It would feel lumpy / ratchety when turning the wheel. Rather than a smooth turn, the wheel felt as though there were many small stops as it was turned. I traced it to hot fluid by hosing the hydro fluid heat exchanger with the tractor running for a few minutes. When the fluid cooled I could hop back on the tractor and it worked normally. I forget what temperature readings I got. Usually it wasn't a problem, but it didn't take much of an air blockage to bring it on when working it hard.

If the grass was really heavy, no blockage was required to make it happen. Only solution then was to slow down.

 

[aerolland]

In the video it looks like raising the box blade (maybe adding to the load by ripping it up through the dirt?) uses enough of the hydraulic output to reduce the flow to the trans.

This could be, but if that's the case I think something is vastly wrong, maybe in the hookups of lines - but I don't think I have anything wrong. The charge pump does all the heavy lifting for the loader and rear lift arms and supplies a small head pressure to the trans pump. If it is putting out it's ~2,000 psi there should be plenty to supply all. Volume is a different animal though, but I would argue since the loader behaves properly and is not slow, there should be enough volume to go around. I do get the feeling that it's starving fluid though...

Rather than a smooth turn, the wheel felt as though there were many small stops as it was turned. I traced it to hot fluid by hosing the hydro fluid heat exchanger with the tractor running for a few minutes.

Interesting observation, I guess I need to get my thermometer out and try to determine actual temperature and see what might be going on around the exchanger. I know the screens are clean because I check them regularly once I learned it likes to run hot. One theory I have had is that a majority of the fluid goes through the loader spool valve and if there was some wear present (and there is) there might be a fluid shear situation occurring which would introduce heat. Hopefully will get my new spool valve installed this weekend - waiting on Surplus Center to deliver a couple needed fittings.

 

[aerolland]

It appears you a starting with a 3000 hour/ ~20 year old non functioning unit and you do not have any real service history of the machine, so there might be an underlying problem which was there before you got the tractor, or it has manifested since you acquired it. This makes fault finding from afar by anyone, a whole lot more difficult.

Totally agree and you can imagine my frustration - definitally testing my patience and knowledge.

reset the main relief back to factory specifications.

Agreed, this was done immediatly once it was determined the change did not make a difference. By the way, since the spool valve has now been changed, the hydraulic loader performance is back up to par with a newer unit - no reason to boost pressures anyways!

Get your parts/service manual out and go over all connections

Have done this many times, making sure I have not overlooked anything

What oil brand and grade did you refill with?

Tractor Supply HST - Traveller Premium (meets Kubota UDT spec). Filled to 100%, if not slightly over the required amount

Did you use the correct Kubota branded filter?

All parts came from local Kubota dealer that my family has been dealing with for over 30 years.

Have you cleaned the hydraulic screen and was there any debris present?

Screen was removed and cleaned while tractor was seperated for clutch maintenance. No major findings in the screen.

Did you replace the orings? Please check all flexible joints and clamps.

Yes and yes.

Did you cut open or notice any debris in the old HST filter?

No, did not cut apart the filter. Should have, however, it was in great shape externally and appeared as though it was changed routinely (or at least once, recently)

Are you certain the HST filter is fitted correctly/square/seal intact/not double seal etc?

Yes.

Do you have a service manual for the tractor?

 

[aerolland]

Have you confirmed that your HST loss is not actually caused by a slipping Clutch disk?

That's an interesting question. I don't think it is slipping based on other usage, i.e. I would think it would slip in low range more often than just when I am using hydraulic flow for 3 pt arms. Any suggestions as to a better way to test it?

It's a brand new disk and pressure plate by the way...

 

[Sabireley]

What ended up being the problem? I have these exact symptoms? When I lift my blade there is a whining sound and no forward motion. Let off the pedal and press again and if goes forward.