3x20 hydraulics? pump

BigMike50 · Sep 7, 2013

ive noticed an issue since day one where you can hear what sounds like cavitation when operating any hydraulic implement. Seems to be an issue most machines where it only happens while the machine is in motion via ehydro pedals. Sometimes the loader will jerk while lifting or sometimes it wont be you will hear a cavitation sound. Same can be said for the operation of the 3 point lift. While doing some thinking, Im starting to think this happens because the sump cannot meet the demand for enough oil while the ehydro is using the oil. I don't know. I can duplicate the situation with the machine in neutral and pushing the ehydro pedal down as well to get the fluid flowing. I have the oil at the full line and yes my inline screen is clean. I have tried to other machines and get the same issue. Maybe some don't notice it. Today I hooked up my gauge to see what the pressure is doing while the noise is happening when working the loader hydraulics. MAybe someone can make sense of it by viewing video of the gauge. If you listen closely, you can hear the cavitation sound while it is doing it. Maybe its just the sound of the hydraulic pressure relief?

tomd999 · Sep 8, 2013

Hiya,

Make sure your sump is full, especially if you operate on slopes.

It's "about" a gallon and a half between "add" and "full" on the dipstick on mine. That's about 12% of total capacity, add a slope into the mix and I can see the pickup sucking some froth or air. I notice the jumpy loader if I'm lower than "full" on the stick, especially if I'm on a slope.

Tom

classic · Sep 8, 2013

BigMike50 said:
ive noticed an issue since day one where you can hear what sounds like cavitation when operating any hydraulic implement. Seems to be an issue most machines where it only happens while the machine is in motion via ehydro pedals. Sometimes the loader will jerk while lifting or sometimes it wont be you will hear a cavitation sound. Same can be said for the operation of the 3 point lift. While doing some thinking, Im starting to think this happens because the sump cannot meet the demand for enough oil while the ehydro is using the oil. I don't know. I can duplicate the situation with the machine in neutral and pushing the ehydro pedal down as well to get the fluid flowing. I have the oil at the full line and yes my inline screen is clean. I have tried to other machines and get the same issue. Maybe some don't notice it. Today I hooked up my gauge to see what the pressure is doing while the noise is happening when working the loader hydraulics. MAybe someone can make sense of it by viewing video of the gauge. If you listen closely, you can hear the cavitation sound while it is doing it. Maybe its just the sound of the hydraulic pressure relief?

What is a 3x20? Is that a new model?

kennyd · Sep 8, 2013

Where is the gauge plugged in?, and why is it reading 2500psi? Are you holding the loader in relief? At the end when the sound changes, what did you do if anything?

kennyd · Sep 8, 2013

classic said:
What is a 3x20? Is that a new model?

"x" can mean 3320, 3520, 3720...

BigMike50 · Sep 8, 2013

kennyd said:
Where is the gauge plugged in?, and why is it reading 2500psi? Are you holding the loader in relief? At the end when the sound changes, what did you do if anything?

sorry Kenny. should have specified that the hose is disconnected for the loader and this is not an inline gauge. The sound and surge is what it it is doing regardless if the hose is connected and when you are rasing the loader. Very difficult to put into words the condition while writing it out. even by going into relief, I can get the machine to not make the noise and have the surge. It just takes not operating the ehydro. Which is why im thinking they are intertwined. I have the fluid actually just a tad over the full mark for good measure

tomd999 · Sep 10, 2013

Hiya,

I think the fluid capacity of the tractor is a wee bit small for the amount of flow that the 3 pumps are pulling in full operation.

If I am correct, the total fluid capacity is just under 7 gallons on the 3x20's, with a combined flow of 8.6g/min for the steering and implement pumps, that means the fluid is cycled fully in under a minute without the hydrostat pump in the picture, add that in and your in the fluid turnover times of 2 to 3 times a minute. That's very fast with very little fluid dwell time to let air separate out, foam to rise and disperse.

If these were a larger chassis, maybe they could redesign the housings to hold more fluid but I'm wondering if some enterprising owner would be able to cobble up an external box to serve as a remote sump or wet chest to add a few gallons to the sump, plum it up to the pump pickup and see if that made a difference.

OK, I'm really tired so don't blast me if this makes no sense, but would be an interesting experiment,

Tom

BigMike50 · Oct 26, 2013

update
thought I would give my update. Took awhile for diagnosis at the dealer. The manufacture had the dealer do a bunch of things twice to try and remedy. The last resort was to swap out the pump with a new one. That fixed the problem and john deere wants them to ship the old part in for analysis. They have been having several tractors having the problem. This has been a problem since new and the tractor has less than 200 hours on it.