2010 hydraulic backpressure

My early model 2010 Wheel (industrial backhoe) has had a variety of over-pressure problems ever since i ended up with it: leaks, blown seals, banging in the lines, etc. It's an H-L-R transmission with power steering.

I teed in a pressure gauge at the output of the cooler, and found that once you raise the RPMs, the pressure on the drain line jumps to about 10-15psi and the lower seal on the steering pinion begins to drip (wheel not being turned).

I started in with the tests described in the manual, and found a steady 120 psi at the accumulator test port, slightly above the spec. However, when I performed the relief valve test (plug the cooler inlet with a gauge), i measured the expected ~45psi at slow idle, but things got wonky as soon as I throttled up. The gauge would start bouncing between about 20 and 60 for several seconds before settling around ~30. The supply line to the filter/regulator assembly also started banging pretty bad.

All the lines are clear and free of kinks, so the only thing I can imagine is too much fluid coming from the external hydraulic pump via the power steering. As I understand it, the external pump runs only the steering, with the remote bypassed under the steering column and the rockshaft line draining back internally (and the shifting itself driven by a separate pump integrated with the driveshaft). There are mentions of an internal divider valve, but not much information about it. If it were to be malfunctioning, could it send all 11gpm to the power steering (instead of the 4gpm the manual implies) and cause backpressure in the rest of the system? Is there any way to test it short of just routing it into a bucket and measuring? Any other ideas on what might cause this behavior?

Thanks

-sb

The first question I have is how does it steer ? If it is hard to steer you maybe looking in the wrong place for the cause.
The flow control valve is # 14 in the attached diagram and the pressure relief valve is # 36, you can take a look at them, just be aware that they may pop out, so be careful in removing and put them back in as they came out.
https://partscatalog.deere.com/jdrc/sidebyside/equipment/82370/referrer/navigation/pgId/249013

(quoted from post at 08:56:30 10/16/21) The first question I have is how does it steer ? If it is hard to steer you maybe looking in the wrong place for the cause.
/navigation/pgId/249013

Click to expand...

steering is good; maybe even a little too good (though i'm probably just imagining that part). With the machine not even moving, I can go across the full range of motion with nearly no effort (2 or 3 fingers will do it)

As far as the valves in the pump go, can they be got at from either underneath or the side cover, or will it involve taking the entire thing out? I'm not sure i'm man enough to split the thing or wrangle it out the bottom.

Thank you for your response

-sb

This post was edited by sbelmont on 10/16/2021 at 11:47 am.

(quoted from post at 19:44:57 10/16/21)

(quoted from post at 08:56:30 10/16/21) The first question I have is how does it steer ? If it is hard to steer you maybe looking in the wrong place for the cause.
/navigation/pgId/249013

Click to expand...

steering is good; maybe even a little too good (though i'm probably just imagining that part). With the machine not even moving, I can go across the full range of motion with nearly no effort (2 or 3 fingers will do it)

As far as the valves in the pump go, can they be got at from either underneath or the side cover, or will it involve taking the entire thing out? I'm not sure i'm man enough to split the thing or wrangle it out the bottom.

Thank you for your response

-sb

This post was edited by sbelmont on 10/16/2021 at 11:47 am.

Click to expand...

ince your steering is good, I don't think their is a problem with the diverter valve or the pressure valve. In all the steering problems, I have encountered either the filter was starving the pump from making adequate pressure or their was a blockage in the diverter valve stopping the flow to the steering box and the steering was hard. You are the first one who ever said they think their is to much pressure being produced. It is my guess that you have a failing seal on the steering motor.
Now to answer your questions : I think they can be reached from underneath, the pump can be removed out the bottom as well, if you know the secret to do so. The biggest problem in doing so is to get the O rings, between the pump and case to stay in place while putting it back in. I would definitely take a closer look at the seal before tackling the pump.
If you truly need/ want to remove the pump, I'll tell you how it's done..

(quoted from post at 17:34:53 10/16/21)
It is my guess that you have a failing seal on the steering motor.

Click to expand...

That was my first guess, and I replaced both the upper and lower pinion seals on the steering motor (dropping the front axle is not a job I want to do again), and they also immediately started leaking.

Is it normal to have up to 15psi on a case drain? Isn't the (center) drain line from the steering motor just for leakage around the pistons, and not supposed to be under any pressure or steady flow at all? Regardless of leaky seals, the hammering in the lines is what has me confused.

Thank you for your response.

(quoted from post at 17:26:56 10/17/21)

(quoted from post at 17:34:53 10/16/21)
It is my guess that you have a failing seal on the steering motor.

Click to expand...

That was my first guess, and I replaced both the upper and lower pinion seals on the steering motor (dropping the front axle is not a job I want to do again), and they also immediately started leaking.

Is it normal to have up to 15psi on a case drain? Isn't the (center) drain line from the steering motor just for leakage around the pistons, and not supposed to be under any pressure or steady flow at all? Regardless of leaky seals, the hammering in the lines is what has me confused.

Thank you for your response.

Click to expand...

t this point, I would agree that 15 psi would be above normal for the case drain. That being said, it's possibly reaching that by excess oil being forced by the piston seals in the steering motor. I'm by no means an expert in hydraulics, what baffles me is their is any pressure reaching the steering motor with out pressure being directed from the steering sector of the steering wheel, maybe I have this wrong but since JD uses open center hydraulics, one would think with out turning the steering wheel the steering sector would simply route the fluid back the case through the return line. With the wheels on the ground, their maybe enough resistance to detect any movement, so raise the front wheels off the ground and see if the wheels drift in one direction or the other. The question remains, is the amount of flow or the pressure causing the effect you are seeing. IMHO the flow would not, while a fluctuation in pressure would cause the hammering in the lines. Since both are controlled from with in the pump, I think you can reach the diverter plug from the round hole on the right side and the pressure bypass plug from the bottom. Take a short piece of dowel and place it on those ares to see if you hear where the hammering noise is coming from.
Post back what results you find, again this is opposite situation of all the steering problems I have encountered.

Edit to this post : Checked with a friend who knows more about hydraulics, he says you have pump cavitation , it causes both increase pressure and hammering in the lines. Causes are restriction in flow to the pump ( filter related ) or air infiltrating of the supply line. With pump cavitation it whips the oil, causing the release of tiny air bubbles to be released. They in turn cause increased/ decrease in pressures causing the effects you are seeing.

This post was edited by Jo Bird on 10/21/2021 at 04:44 am.