NX 5010HST Cab reverse intermittent and jerky

[YLee Kioti]

Have you gone to the dealer you bought the tractor from and asked to see what brand they use to service the machines?
I did and they used a local branded fluid from a Texas distributor.

The jerking was not as prominent as many mentioned here but has almost gone away with the third change out using Kubota's fluid.
Before that used NAPA's Coastal brand full synthetic on the second change out. Fifty hours on Kubota's fluid and do not see/feel any performance difference.

Now that's it's about 104* out here and after a few hours the machine may have a jerky response... when first engaging to travel reverse.

Since each brand has different additive packages.....maybe comparing the brand your dealer uses versus others up for consideration will help in deciding which to go with.....
And I did my first fluid change at 200 hours to remove fines from hyd. system,....but that's just me OCD to fault......(yeah I don't like it either....lol)

 

[TN8Man]

Have you gone to the dealer you bought the tractor from and asked to see what brand they use to service the machines?
I did and they used a local branded fluid from a Texas distributor.

The jerking was not as prominent as many mentioned here but has almost gone away with the third change out using Kubota's fluid.
Before that used NAPA's Coastal brand full synthetic on the second change out. Fifty hours on Kubota's fluid and do not see/feel any performance difference.

Now that's it's about 104* out here and after a few hours the machine may have a jerky response... when first engaging to travel reverse.

Since each brand has different additive packages.....maybe comparing the brand your dealer uses versus others up for consideration will help in deciding which to go with.....
And I did my first fluid change at 200 hours to remove fines from hyd. system,....but that's just me OCD to fault......(yeah I don't like it either....lol)

I'm bringing my tractor back in next week so I will get the fluid info then.

 

[justman777]

I'm bringing my tractor back in next week so I will get the fluid info then.

I'm going to put some Mobile 424 in mine and see what it does.

 

[TN8Man]

I'm going to put some Mobile 424 in mine and see what it does.

I will probably do the same once I figure out the best fluid for my application.

I did discover my cooling fan belt was loose, more than twice the spec. I could turn the fan by hand with little pressure. Not sure how much difference this will make but it needed to be adjusted.

 

[justman777]

Changed out my fluid to Mobile 424, and didn't make a lick of difference. At least now I know I have good fluid!

I managed to take a video of the aeration in my hydro reservoir. You can see the video here. There's no sound.

I start the tractor about 10 seconds into the video, and the aeration starts within seconds after. It looks pretty cool, but I don't think it's supposed to do that.

 

[Citydude]

Changed out my fluid to Mobile 424, and didn't make a lick of difference. At least now I know I have good fluid!

I managed to take a video of the aeration in my hydro reservoir. You can see the video here. There's no sound.

I start the tractor about 10 seconds into the video, and the aeration starts within seconds after. It looks pretty cool, but I don't think it's supposed to do that.

Good luck. This has to be madding for you. But glad you got the root cause figured out. Leak in the suction side.

 

[justman777]

Good luck. This has to be madding for you. But glad you got the root cause figured out. Leak in the suction side.

Maddening, yes. At this point, I'm not sure it's a suction side leak as the fluid returns aerated to the sump within seconds of me starting the tractor. It seems like it should take longer to make it through the pump and return. I know a suction side leak is the most likely culprit, but we've changed out just about every suction side component that may have caused a leak---o-rings, filters, filter housing, pump, clamps, etc.

 

[TN8Man]

I did finally got some answers from a hydraulics expert. For the life of me I could not find the answer to "What is the maximum operating temperature for a tractors hydraulic fluid before it starts oxidation and degradation?". The answer is 180F. I was measuring 209F on the outside metal below the the hydro fill port when my tractor started malfunctioning. (loss of reverse travel and hydro system pulses/jerks).

I was also told the Aeration (foaming or frothy) hydro fluid could be the cause of the hydro fluid overheating. And Aeration is typically caused by the tank too low on fluid or a suction side leak.

Other causes of hydro fluid overheating are:
Defective cooling
Oil level too low
Wrong bypass valve setting
Malfunction of other valves
Volumetric efficiency loss of pump due to wear, etc.
Internal leakage across actuators and valves
And many more.

So in my case it's the aeration that is probably causing the overheating and the malfunctioning of hydraulic systems.

 

[dusty3030]

Looking at justman777's video, the bubbles form quickly.
So which side of the hydraulic circuit is it coming from?

I had my heating issue with the factory third function valve and it's undersized power beyond and return to tank hoses and fittings.
I took apart the rear remote valve and I don't see anything in there that would restrict flow, it appears to be correctly sized. What I haven't inspected or taken apart is the the three point hitch valve area which would be the last place in that circuit.

The other place it could be coming from is the power steering / HST side of the circuit. In that case I really don't know how you could really inspect things.

What I wish I did know was what is the split in flow between the two sides? I can find the total flow gpm but not the split. Anyone know?

 

[justman777]

Looking at justman777's video, the bubbles form quickly.
So which side of the hydraulic circuit is it coming from?

I had my heating issue with the factory third function valve and it's undersized power beyond and return to tank hoses and fittings.
I took apart the rear remote valve and I don't see anything in there that would restrict flow, it appears to be correctly sized. What I haven't inspected or taken apart is the the three point hitch valve area which would be the last place in that circuit.

The other place it could be coming from is the power steering / HST side of the circuit. In that case I really don't know how you could really inspect things.

What I wish I did know was what is the split in flow between the two sides? I can find the total flow gpm but not the split. Anyone know?

The split in the flow between the loader functions/3 point lift and the HST/Steering appears to be the pump. The hydro pump is a dual pump. See the flow routing diagram on the thread here.