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

[Volfandt]

Back in my bikeing days, one modification I did to an old Harley was to install a truck power steering oil cooler in the oil tank return line and this cooled the engine oil considerably. The engine ran cooler, especially in traffic.
HD later came out with a factory oil cooler but it had a thermostat builtin and it's function was to bypass the oil around the cooler until it reached a preset temp.

As for the HST on a tractor, it would be very easy to splice in another smaller oil cooler. One that comes to mind is one that comes in those kits you can buy thats part of a towing package for trucks & SUV's. COurse they still make those power steering coolers too

Thing is, Kubota makes a high quality tractor and I'm sure they've engineered them to the best of specs so would adding an additional cooler effect proper HST warm up?

If I were to add an additional cooler I'd think about a bypass thermostat as theres several warnings in my BX23 owners manual about not operating the tractor until the HST is warmed up.....

Volfandt

 

[biker128pedal]

If you have high hours maybe the coolant system needs flushing. Also, is your air filter clean?

Mike

 

[dillo99]

I have never had a problem with my 7500. Have worked it hard in temperatures in the low to mid 90's. We don't get much hotter than that.

 

[hwew]

Back in my bikeing days, one modification I did to an old Harley was to install a truck power steering oil cooler in the oil tank return line and this cooled the engine oil considerably. The engine ran cooler, especially in traffic.
HD later came out with a factory oil cooler but it had a thermostat builtin and it's function was to bypass the oil around the cooler until it reached a preset temp.

As for the HST on a tractor, it would be very easy to splice in another smaller oil cooler. One that comes to mind is one that comes in those kits you can buy thats part of a towing package for trucks & SUV's. COurse they still make those power steering coolers too

Thing is, Kubota makes a high quality tractor and I'm sure they've engineered them to the best of specs so would adding an additional cooler effect proper HST warm up?

If I were to add an additional cooler I'd think about a bypass thermostat as theres several warnings in my BX23 owners manual about not operating the tractor until the HST is warmed up.....

Volfandt

Exactly!!

The worst thing to do is to oversize the oil cooler.

There are some oil coolers that I am thinking of that have a bypass built in so when the oil viscosity is thicker the oil will bypass the oil cooler section.(the more the oil viscosity thins out the more it cools) I guess the thing to do is contact the oil cooler manufacture and see if these coolers will work with HST fluid and then contact try to contact someone in Kubota and find out what would be the optimal temperature for the HST fluid to be and then contact the oil cooler manufactuer and see if they have one that will meet our specs.

I have one of these coolers that I had on a Diesel Chevette. Before I sold it I pulled it off and and put it away for some other use. I believe it was around $60.00. I need to pull it out and see what company made it.

 

[hwew]

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

Good point!!

On most applications I feel you are right.
But mowing on level ground and slight grades should not be a problem with these tractors. (Mowing on Level ground in Low range at 3.9 mph. top speed would be a very long day for some of us. I go at roughly 4-6 mph. at times on level ground)

Using a loader, blade, pulling a good load or mowing up steep hills I would use low range for sure.

There is nothing written in the manual that states which range to use.

I believe it would be good for Kubota to go over this so everyone understands what the limitations are in the ranges.

Thanks for bringing this up.

 

[ronjhall]

Back in 2001 when I did some checking of HST oil temperature it was noticed that HST oil temperatures would run about 100 degrees above ambient temperatures. Your temperatures are within those limits. How many hours do you have on your HST oil?

 

[hwew]

Back in 2001 when I did some checking of HST oil temperature it was noticed that HST oil temperatures would run about 100 degrees above ambient temperatures. Your temperatures are within those limits. How many hours do you have on your HST oil?

Aprox. 100 hrs.

 

[hwew]

I just finished mowing for three hours and found out some new results.

First of all instead of running the engine at full rated RPM (that is recomended in the Kubota mower manual) I ran the RPM's at 2200 RPM for the three hours.

The out side temperature was the same as yesterday, 93 deg. F. (34 deg C.)
The mowing conditions were exactly the same.

Well the results are as follows:

The steering never got jerky. It worked fine the whole time!
HST fluid temperature to the oil cooler was 158 deg. F. (70 deg. C.)
Did not test temp drop from the cooler because it should be about the same as the first test.

Here are the first readings from yesterday:
Feed Line to oil cooler-------176 deg. F. (80 deg. C.)
Return Line Trans Axle-------171 deg. F. (77 deg. C.)

I think we need to get Kubota involved in this A.S.A.P.

Running new Super UDT Fluid, New filters and HST Transmission Strainer spotless.

Are we getting cavitation in the pumps at high RPM's? I HOPE NOT!!

This tractor only has 220 HRS.!!

I read other forms in tractorbynet that others with B series tractors are having jerky steering. And one person went threw having the powersteering unit replaced by the dealer and it solved nothing.

Does anyone have any sugestions how to approach Kubota with this problem.
Or knows someone at Kubota that might be able to help us out.

 

[Sully2]

Dont know about where YOU live...but I contacted Chevron here about their fluid...LOL...ONLY way I could buy it HERE was "bulk" which meant 1500 gallon quantities!! ( just a tad bit of "overkill" for my needs)

 

[Sully2]

Exactly!!

The worst thing to do is to oversize the oil cooler.

There are some oil coolers that I am thinking of that have a bypass built in so when the oil viscosity is thicker the oil will bypass the oil cooler section.(the more the oil viscosity thins out the more it cools) I guess the thing to do is contact the oil cooler manufacture and see if these coolers will work with HST fluid and then contact try to contact someone in Kubota and find out what would be the optimal temperature for the HST fluid to be and then contact the oil cooler manufactuer and see if they have one that will meet our specs.

I have one of these coolers that I had on a Diesel Chevette. Before I sold it I pulled it off and and put it away for some other use. I believe it was around $60.00. I need to pull it out and see what company made it.

The fluid is going to reach its proper operating temp..REGARDLESS of how large a cooler you install!! Only difference is HOW LONG it may take for it to "warm up". Your not going to "hurt" the fuild even by installing a cooler thats rated for 24 thousand pounds GVW...but you can bet in mid winter there would be a LOOONNNGGG time till the fuild got warmed up with a cooler that large!

Before Id ever go to swapping coolers themselves...Id install an electric fan in front. Operated by a thermistor (SP?) that at "X" temp the fan kicks on...with a manual switch overide so I could run it 100% of the time is needed.