NX6010 suction side hydro leak

[justman777]

I don't have a manual handy, but where does the pump take suction from the sump? Is there an internal dipper tube with a screen on the suction line? With all of the troubleshooting you have done (which seems well done) it seems there is a considerable restriction in the suction, causing a much lower than usual pressure in that suction line, effectively boiling the oil due to the lower pressure (cavitation). Is there a way you can check the suction pressure, and compare that to typical suction pressure of the same type unit? This would let you know if there is a crushed dipper tube, or clogged suction screen in the sump, if there is one, or any type of restriction.

Also, I know that a number of these tractors hydraulic pumps take suction from the sump AND the power steering pump. Maybe there is something happening there?

This may have already been done, but I wanted to mention.

The pump takes suction from the sump directly via a 1.5 inch(ish) tube that runs from the bottom of the sump, through a filter, and then to the pump. There isn't a screen prior to the filter that I can recall. Also, no dip tube.

The pump is a dual pump in that it splits the hydraulic flow into two separate fluid paths. Once side feeds the loader and a few other functions, and the other side feeds the steering, HST, and a few other functions.

I've also looked at the clear line I have installed in the suction side and get zero bubbles when I initially start up the tractor. I only get bubbles after its ran for a while, which tells me the fluid is returning to the sump aerated and filling up the sump. I start getting bubbles when the aeration makes its way to the bottom of the sump. With the high flow of these machines and the smallish reservoir, that takes about 15-20 seconds. That tells me the aeration is occurring at or after the pump. The video I shot the other day of the aerated fluid coming out about 3 seconds after I start the tractor would seem to indicate the aeration is occurring very close to the sump. I presume that's why Eric asked me to check the screen at the end of the banjo bolt on the return line adjacent to the remote valve stack.

I think my next step is to leave my tractor where it is and repeat my test cycle. That way, I'll know I don't have any aeration from moving it, and it'll have had more than enough time to settle.

 

[TN8Man]

I bought the tractor from Larry Stovesand Equipment in Murfreesboro but the nearest dealer/shop is Snyder's Tractor & Equipment in Sparta.

 

[LouNY]

Do you have a hydralic flow diagram for your tractor,
You mention that pump flow splits.
Many off the newer small tractor have two engine driven pumps,
one is for all the remote hydraulics, the loader, rear remotes and lift arms.
The other smaller pump is for the power steering.
The hydrostatic drive has it's own internal pump which may use the steering pump as a "charge" pump.
The hydros main pump is always running as long as the engine is coupled to it.

It might make an interesting point if the external pump was provided it's own reservoir temporarily such as a full clean 5 gallon bucket allowed to just recirculate in it and see if your main reservoir still becomes airated or stays good and the bucket becomes airated.

That would determine if the hydraulic loop was the issue or the hydrostatic unit is.

 

[justman777]

Do you have a hydralic flow diagram for your tractor,
You mention that pump flow splits.
Many off the newer small tractor have two engine driven pumps,
one is for all the remote hydraulics, the loader, rear remotes and lift arms.
The other smaller pump is for the power steering.
The hydrostatic drive has it's own internal pump which may use the steering pump as a "charge" pump.
The hydros main pump is always running as long as the engine is coupled to it.

It might make an interesting point if the external pump was provided it's own reservoir temporarily such as a full clean 5 gallon bucket allowed to just recirculate in it and see if your main reservoir still becomes airated or stays good and the bucket becomes airated.

That would determine if the hydraulic loop was the issue or the hydrostatic unit is.

Hello! I do have a hydraulic flow diagram for my tractor. Found it here, and looks to be straight from the service manual.

This tractor has a single pump, but it's actually two pumps in the same unit.

 

[MinnesotaEric]

The pump takes suction from the sump directly via a 1.5 inch(ish) tube that runs from the bottom of the sump, through a filter, and then to the pump. There isn't a screen prior to the filter that I can recall. Also, no dip tube.

The pump is a dual pump in that it splits the hydraulic flow into two separate fluid paths. Once side feeds the loader and a few other functions, and the other side feeds the steering, HST, and a few other functions.

I've also looked at the clear line I have installed in the suction side and get zero bubbles when I initially start up the tractor. I only get bubbles after its ran for a while, which tells me the fluid is returning to the sump aerated and filling up the sump. I start getting bubbles when the aeration makes its way to the bottom of the sump. With the high flow of these machines and the smallish reservoir, that takes about 15-20 seconds. That tells me the aeration is occurring at or after the pump. The video I shot the other day of the aerated fluid coming out about 3 seconds after I start the tractor would seem to indicate the aeration is occurring very close to the sump. I presume that's why Eric asked me to check the screen at the end of the banjo bolt on the return line adjacent to the remote valve stack.

I think my next step is to leave my tractor where it is and repeat my test cycle. That way, I'll know I don't have any aeration from moving it, and it'll have had more than enough time to settle.

I read your systematic post.

By hook or crook, has the hydro and HST filters been swapped out? Easier to have a defect in either of those than some weird, aerating restriction somewhere.

 

[LouNY]

I've read many of the posts on this thread, but not all.
What I see is every thing chasing a suction leak in the auxiliary side of the system.
The portion of the external pump that goes to the steering and oil cooler and to the HST is just a charge or make up fluid for the HST.
It seems that the issue you are having is in the HST its self, a suction leak in that pump.

Hydrostatic Drive Operation

 

[justman777]

I've read many of the posts on this thread, but not all.
What I see is every thing chasing a suction leak in the auxiliary side of the system.
The portion of the external pump that goes to the steering and oil cooler and to the HST is just a charge or make up fluid for the HST.
It seems that the issue you are having is in the HST its self, a suction leak in that pump.

Hydrostatic Drive Operation

That could possibly be! I'm not discounting anything at this time. If someone has the workshop manual for the NX series and could verify the location of the HST pump and how it's plumbed, that'd be telling.

 

[justman777]

I read your systematic post.

By hook or crook, has the hydro and HST filters been swapped out? Easier to have a defect in either of those than some weird, aerating restriction somewhere.

Wouldn't that be something! But no. I've confirmed the smaller rounded HST filter is on the HST side and the larger hydro filter is on the suction side.

 

[MinnesotaEric]

Wouldn't that be something! But no. I've confirmed the smaller rounded HST filter is on the HST side and the larger hydro filter is on the suction side.

What I'm asking is if you have changed out those filters.

 

[justman777]

What I'm asking is if you have changed out those filters.

Oh! Yes, they were changed at the 50 hour service when I bought the tractor. The hydro filter has been changed one other time during troubleshooting.