B7500 HST power steering and and 3 point lift problems in high temp.

[hwew]

Does anyone else have problems with there B series HST. tractor power steering and 3 point hitch lift after running thier tractor in hot weather for over an hour.
I noticed that my power steering gets jerky and I start loosing lift capability and I am getting worried. I am using Super UDT.

It seems like it could be an over heating issue in the hotter weather.
I had this happen once last year at around 125 hours but did not think it was important because it did not do it again.
But lately I have been mowing in hot weather and it has been happening very often.

The funny thing is when you let it cool down for about ten min. then it works fine untill you use it for about ten or fifteen min. The HST fluid is not over filled. Filters are changed every 50 hours. HST screen cleaned first 50 hours and every 100 hours after. HST fluid changed first 50 hours and every 100 hours after.

It does not do this in cooler weather.

I have been thinking about the oil cooler on the B series tractor. How much BTU's of heat does it actualy dissipate? Could it be under sized?
I looked at the larger Kubota tractors and they seem to have a better oil cooler (Not a piece of wavy tubing in front of the radiator. I also looked at a New Holland TC 30 HST and it has a true oil cooler also.

I guess I need to get oil temp readings once it starts happening.

Has anyone tried installing a better HST oil cooler on thier B series tractor?

I went to my dealer today and went over what is happening. The response was it could be that the Super UDT might not be able to take the heat like regular UDT or other HST oils.
The dealer said from what they understand is Super UDT is for places with cooler climates and it is not needed here in North Carolina.

I am thinking of trying a Full Synthetic HST oil first before installing a differant oil cooler.
Any opinions on Synthetic HST oil.
Cheveron? Amsoil?

 

[Bob_Young]

You've probably covered this already, but I'll post it anyway.

If your cooler is like mine (B7610), it's mounted ahead of the radiator and being cooled by the air coming through the grille before it gets to the radiator. Have you been keeping the grille clean? I brush mine out every 4 or 5 hours when mowing. How about the screen ahead of the radiator and the radiator itself? The fan has to draw air through both of these to get flow past the oil cooler. If they're dirty or clogged, air flow will be reduced. When brushcutting, I have to pull the screen at least once a day to clean that.

A certain amount of trash gets past both the grille and the screen and ends up lodged in the radiator. I'm surprised how much this is at times. I clean that by blowing out with high pressure air. Depending on usage/conditions, it might be needed a couple of times a week. While you've got the hose out, hit the oil cooler itself.

Don't forget to check the fan itself. Missing or damaged fan blades can hurt efficiency.

Is the tractor running a little warmer than usual? That could be an indication that airflow up-front isn't what it should be. Kubotas aren't as forgiving as the old Farmalls and JDs of yore. They are an efficient design and rely upon every subsystem doing its job and performing within spec.

Actually, I'd be a bit surprised if heat alone (within reason) could do this. I'm wondering if something is opening up with heat and letting air into the system or if some water trapped in the system is reverting to steam.
Bob

 

[hwew]

Front Grill, Radiator Screen and radiator all spotless.
Engine Temp. Stays just above the C.

I have done some research and found out some intresting stuff.

From what I found. Kubota Super UDT does not protect as well in the higher temperatures as well as Kubota UDT. (I am refuring to temp. at 100 deg.C).


Kinematic Viscosity @ 100°C, cSt:

Kubota Super UDT---------------------------------------------9.0
Kubota UDT---------------------------------------------------9.5
Chevron Synthetic All-Weather THF----------------------------9.5
AMSOIL Synthetic Tractor Hydraulic/Transmission Oil (ATH)-----9.7


Viscosity Index:

Kubota Super UDT---------------------------------------------192
Kubota UDT---------------------------------------------------140
Chevron Synthetic All-Weather THF----------------------------204
AMSOIL Synthetic Tractor Hydraulic/Transmission Oil (ATH)-----159

The specs. that I am concerned about that are listed above is Kinematic Viscosity @ 100°C, cSt.


I just remembered something.
Before I Got my B7500 I had a BX2200 simmilar things would happen in the HOT weather. It lost lift capability. I always ran Super UDT. I think I listed it in another post years back.

My dealer could be right about sticking to UDT in the summer months.

Anyways, It seems to point to a cooling issue in the extreem HOT weather.

It will be HOT this week and I have some mowing to do I will get my Temp. probes out and Duct Tape them on the Input and Return of the cooler tubes and hook them up to my Fluke 52II Thermometer and see how HOT the HST oil is getting at input and how much it is cooling at return.

But for now I think I will try differant HST oil.

It seems that Kubota UDT, Chevron or Amsoil would offer good protection in HOT weather.

This would be a good question to bring up to Kubota.

 

[rdsaustintx]

This may be of limited applicability here, but I have noticed odd stuff in the hot weather on my BX23 (full of SUDT). I have been flogging the thing in very hot (100+) weather lately, using a box blade which is too big on soil which is too rocky. 80 hours in 10 days.

After 30 minutes or so, I can feel a little jerk in the steering every time I hit the 3ph valve. It worries me, but the tractor keeps chugging and I got TONS of dirt to get moved. Plus I got 5 months of warranty left, so if I'm gonna pop something I want to do it now.

I also can definitely hear a difference in the hydro pump and the sound of the flow through the BH bypass when it's hot.

After it cools down it operates normally. My machine has no oil cooler, so I wonder if it's just getting a little too hot for the SUDT.

I have a (300hr) fluid change coming up and already have SUDT on hand. but at 600hr (and out of warranty) I plan to switch to Amsoil, unless somebody here talks me out of it.

Russell in Texas

 

[hwew]

I here you.

It sounds that you are experiancing the same simptoms that I had on my BX2200 before I got rid of it. And pretty much the same simptoms that I now have on my B7500.

It has to be heat related. I am still waiting for a nice HOT day to run some tests of my own to see how hot the HST fluid gets in 90+deg. weather.
As soon as I run the test I will post the results.

I believe we will be looking for a HST fluid that would offer the most protection in Hot weather. And hopefully the same HST fluid can be used in cold weather.

From what I have found out so far is the Amsoil and Chevron Synthetics are the best products for HOT weather protection.

I know the Chevron product would work fine in cold weather.

About Amsoil, I am not sure and am still looking into it.
The only reason I am holding back on my decision to use Amsoil is they Spec. it out as UDT and from what I read on Specs. Amsoil does not flow as well in colder weather as Chevron.

But Amsoil has a slight edge in HOT weather protection. But is it enough?

But the question is will any of these products actually help us out.

And that is why I feel the first important step to take is to see how hot the HST fluid is getting.

 

[don716]

I also have a B7500 I bought new in 2003 and it has been fine until lately since its been so hot.I have noticed a little jerking myself with the P/S when it gets hot.I also use SUDT.I thought I was overlooking the P/S dipstick or something and called my dealer.He said it ran off the hydrolics so I thought my P/S was going out since it has never done this before.It sounds like we are all in the same boat.If you find out anything let us know.I live in Georgia so it gets hot here too.
Donny

 

[hwew]

I am hopeing for a hot day tomorrow.

If it is hot I will get out and run the B7500 and take some readings and post it A.S.A.P.

 

[Bob_Young]

A question, hwew. When you mow do you mow in high range or low range? If high, could you get enough speed by running in low with the pedal down all the way? If low, could you try high range with the pedal just 'cracked'? If you're able to get some temperature readings, it would be interesting to compare 'same speed' operation in the different ranges.

I'm wondering if changing range, but operating at the same speed, might make the HST run cooler. I'd suspect it would run its coolest in low range, but I don't know HST very well.
Bob

 

[hwew]

Well here are the results.

Out side temp.------93 deg. F. (34 deg. C.)

Ran B7500 tractor in high range for 3 Hours untill steering started to get jerky.

Readings are as follows:
Feed Line to oil cooler-------176 deg. F. (80 deg. C.)
Return Line Trans Axle-------171 deg. F. (77 deg. C.)

Temperatures would of been higher if I mowed on hills.

I can see temperature on HST fluid approching 100 deg C. or possably exceed 100 deg. C. If you work a front end loader, mow on hills or or working a box blade or some other attachment in hot weather at 90+ deg. F.

I would say it might be wise to run a Synthetic HST fluid in hot weather.
I feel the readings above indicate that the B series HST tractors including other models with HST run high HST fluid temperatures in hot weather.

The reason I include others is all new B series tractors up to the B7800 use the same or same type of oil cooler and they could have the same problems that the B7500 HST tractor has. I know that the BX series tractors HST fluid get very hot.

The question now is what would be the best solution.

If we need to install a differant oil cooler to keep temperatures to a safe level. What type and size of oil cooler do we need?

I guess another good question would be what is a safe temperature level for HST fluid in these tractors.

If Kubota engineers are reading this form what advice can they give us.

I guess it is time to contact Kubota first before we do anything. Lets try to get them involved first. They built a great tractor I think they can figure this problem out.

 

[Doc_Bob]

Ran B7500 tractor in high range for 3 Hours untill steering started to get jerky.

I don't have a HST, but I thought high range was for moving, not working?
Bob