JD 2720 Hydraulic Issues

smashedtoe · May 23, 2023

Hi.

I have an interesting one which I am suspecting with get one of two responses:

Crickets
You should talk to the guy who changed the charge pump

Here is why I am here typing to you today.

I replaced the charge pump in my JD 2720 as I was experiencing some steering related issues and the PTO quick working. Ended up finding the inner charge pump rotor broken and a sheared key on the shaft; pump changed with no issues.

Start the tractor, PTO works amazingly however, the steering is still almost non-responsive and there appears to be some air in the lines. Here is where things get a little weird; when I engage the PTO the steering improves (not perfect) but the hydrostatic drive whines more.

I am suspecting a relief valve and praying for a miracle.

Oil levels fine, but when I loosen the test port on top of the charge pump the oil is filled with plenty of little bubbles and "appears foamy" which settles down to clear oil after a few moments. I loosen another line and air seems to "burp" out, but I dont know if this is normal and I should continue to run the tractor/add oil to purge any air?

Any help would truly be appreciated.

Thanks

Jeff

beenthere · May 24, 2023

Seems you have a couple years of problems that may, or may not include this pump. How do they all tie together, or do they not at all ??
Feel sorry for your problem, but wonder if there is a common thread here that is important to a solution for you. Hang in there.

John Deere 2720 - Zero Hydraulics, Zero 3-Point Hitch, Zero Answers...

Hello all. First, my apologies if I am posting this in the incorrect location. I have a John Deere 2720 with 419 hours. Approximately 3 months ago i noticed the hydraulics (loader, snow blower) and 3-point hitch were moving much slower than usual so I did what every other newbie would do...

www.tractorbynet.com

John Deere 2720 - Kanzaki Hydraulic Pump

Hello all, I am looking for a rebuild kit for the Kanzaki PW1-D-8A hydraulic pump off my John Deere 2720 utility tractor. Interanal rubber gasket/seal (?) is broken and I can not justify spending $700 CAD on a pump when the aforementioned seal is the issue. Anyone here know where I can...

www.tractorbynet.com

John Deere 2720 Hydraulic Pump Seal Issues

Good Day all. I have a John Deere 2720 compact tractor which I just repaired by installing a new hydraulic pump. Everything seemed fine, but for some reason the shaft seal keeps blowing and leaking hydraulic oil into the engine. Any suggestions or recommendations as to what would cause...

www.tractorbynet.com

John Deere 2720 No PT0 No Power Steering....No Clue

Hello once again friends. Okay I am faced with another issue with my JD 2720 and I am looking for some advice.....and no, not the advice which suggests a different colour tractor, etc. This past winter during an extreme cold snap (-42C) my son wanted to be helpful and clear some snow. He...

www.tractorbynet.com

seville009 · May 24, 2023

Make sure that the hydraulic filters are tight; not letting a little bit of air in. They probably are fine, but you never know…..

smashedtoe · May 26, 2023

beenthere said:
Seems you have a couple years of problems that may, or may not include this pump. How do they all tie together, or do they not at all ??
Feel sorry for your problem, but wonder if there is a common thread here that is important to a solution for you. Hang in there.

John Deere 2720 - Zero Hydraulics, Zero 3-Point Hitch, Zero Answers...

Hello all. First, my apologies if I am posting this in the incorrect location. I have a John Deere 2720 with 419 hours. Approximately 3 months ago i noticed the hydraulics (loader, snow blower) and 3-point hitch were moving much slower than usual so I did what every other newbie would do...

www.tractorbynet.com

John Deere 2720 - Kanzaki Hydraulic Pump

Hello all, I am looking for a rebuild kit for the Kanzaki PW1-D-8A hydraulic pump off my John Deere 2720 utility tractor. Interanal rubber gasket/seal (?) is broken and I can not justify spending $700 CAD on a pump when the aforementioned seal is the issue. Anyone here know where I can...

www.tractorbynet.com

John Deere 2720 Hydraulic Pump Seal Issues

Good Day all. I have a John Deere 2720 compact tractor which I just repaired by installing a new hydraulic pump. Everything seemed fine, but for some reason the shaft seal keeps blowing and leaking hydraulic oil into the engine. Any suggestions or recommendations as to what would cause...

www.tractorbynet.com

John Deere 2720 No PT0 No Power Steering....No Clue

Hello once again friends. Okay I am faced with another issue with my JD 2720 and I am looking for some advice.....and no, not the advice which suggests a different colour tractor, etc. This past winter during an extreme cold snap (-42C) my son wanted to be helpful and clear some snow. He...

www.tractorbynet.com

This really has been a frustrating one with this tractor; oddly enough so low hours on it (I purchased it brand new so I know the hour meter is bona fide).

I had a fella call me today and thought maybe some debris from the sheared charge pump key is caught in a relief valve which is a little scary as i would have no idea how to clear that out. Also had some great suggestions to check tomorrow morning; sump screen, loose/plugged filter or plugged orifice.

Needless to say, I went to JD today and eyed up a new 2038R but my stubborn side says "hang in there Jeff....the solution is right under your nose."

I am going to buy a pressure gauge tomorrow as well and see what the pressure is testing at....for my own sanity.

Time for this good run of bad luck to run out.

Thanks to you all for your support, suggestions and ideas. You have no idea just how grateful I am for this forum.

smashedtoe · May 26, 2023

beenthere said:
Seems you have a couple years of problems that may, or may not include this pump. How do they all tie together, or do they not at all ??
Feel sorry for your problem, but wonder if there is a common thread here that is important to a solution for you. Hang in there.

John Deere 2720 - Zero Hydraulics, Zero 3-Point Hitch, Zero Answers...

Hello all. First, my apologies if I am posting this in the incorrect location. I have a John Deere 2720 with 419 hours. Approximately 3 months ago i noticed the hydraulics (loader, snow blower) and 3-point hitch were moving much slower than usual so I did what every other newbie would do...

www.tractorbynet.com

John Deere 2720 - Kanzaki Hydraulic Pump

Hello all, I am looking for a rebuild kit for the Kanzaki PW1-D-8A hydraulic pump off my John Deere 2720 utility tractor. Interanal rubber gasket/seal (?) is broken and I can not justify spending $700 CAD on a pump when the aforementioned seal is the issue. Anyone here know where I can...

www.tractorbynet.com

John Deere 2720 Hydraulic Pump Seal Issues

Good Day all. I have a John Deere 2720 compact tractor which I just repaired by installing a new hydraulic pump. Everything seemed fine, but for some reason the shaft seal keeps blowing and leaking hydraulic oil into the engine. Any suggestions or recommendations as to what would cause...

www.tractorbynet.com

John Deere 2720 No PT0 No Power Steering....No Clue

Hello once again friends. Okay I am faced with another issue with my JD 2720 and I am looking for some advice.....and no, not the advice which suggests a different colour tractor, etc. This past winter during an extreme cold snap (-42C) my son wanted to be helpful and clear some snow. He...

www.tractorbynet.com

Oh, I nearly forgot to respond beenthere...

So the first two hydraulic pump postings are not related to the latter two. Albeit these are both odd scenarios as the JD dealership Parts Depts. have no record of ordering these parts for anyone in the past...heh heh heh....definitely not the external pump (thank you to Yanmar for that).

I have grown up on JD and continue to use these machines every day....maybe this 2720 should have been painted Lemon Yellow. I dont know but I do know I am not going down without a fight.

oldnslo · May 26, 2023

A couple of questions come to mind.
1) What caused the original charge pump to fail. Did it seize or get scored generating debris that went into the system.

2) Is steering, PTO and charge all from same pump? Suspect yes from symptoms

Do you have service manual with hydraulic schematic? If yes can you please post it since that could help us arm chair mechanics determine items to check.

Deere normally is good about having test ports for doing diagnostic work.

smashedtoe · May 27, 2023

Hello oldnslo (love that name!)...

I believe what caused the pump to fail originally was my son started the tractor during extremely cold weather without allowing a warm up period, placed it in High Range and proceeded to back out of the cold storage shop. Tractor reversed about eight feet and quit moving (suspecting this is when the key sheared on the shaft/breaking inner rotor on charge pump).

Yes, the steering and PTO function off the charge pump; implements work off an external, engine mount pump.

I do have the JD Technical Manual and have attached some pages as requested.

Thank you so much!!

oldnslo · May 27, 2023

Smashedtoe ( been there done that also)
in looking at schematic valve O the charge regulator is what also supplies excess oil to PTO circuit. I would start by checking your charge pressure since you stated engaging PTO seems to help steering but now HST whines. Charge is critical so you don’t damage the very expensive HST.

next I would check steering pressure since should be secondary pressure compared to charge.

Cold oil shouldn’t cause the pump to shear drive if system is designed properly. That being said my Branson blew the HST filter from cold oil and system not being designed to allow cold oil flow so definitely could be the cause.

admire your attitude of stubbornness will overcome common sense

smashedtoe · May 27, 2023

This is where I begin to draw a blank as i have no idea where to find "Valve O" or where to place my pressure gauge to test? Come on Google!! What you are saying does make sense though oldnslo.

I believe I know which port to tie into to check the steering pressure....read that in the technical manual. As soon as the Traeger has dinner ready and my belly is full I will venture back into the shop and see what the gauge tells me.

Thank you so much for the feedback!

oldnslo · May 27, 2023

I am surprised that the service manual does not have a trouble shooting or diagnostic section for the HST and steering. Is there another section in the manual for diagnostics?
Schematic shows what I suspect is a test port for pump pressure but the section you posted certainly does not state where it is.

As a point of reference valve O is drawn as pressure reducing valve vs relief valve but again where is it and where is test port for charge vs steering vs PTO?

smashedtoe · May 27, 2023

The technical manual does provide some info (see attached). Not a lot for diagnostics though which is surprising.

oldnslo · May 28, 2023

Smashed,
Since the charge circuit is fixed displacement pump we can use the theory that when the pump is turning the oil must go some where and that it will flow to the point of least resistance.

In reviewing the schematic from the service manual it would indicate their four potential flow paths.
1) Across valve O and into the HST for make up oil for leakage losses.
2) Through the PTO circuit. Note: I suspect there should be an orifice in this circuit to control PTO clutch engagement speed but is not shown in schematic.
3) Through valve M to steering. This is where majority of oil would typically since goes through steering unit, then through heat exchanger and back to tank.
4) Across main relief valve L. L would have to be stuck open at pressure lower than M or you would not have any steering.

The service manual shows how to check for steering pressure M, system pressure L. Also shows how to test PTO pressure K. Since steering is not working properly oil is going through another leak point either into the HST, through PTO or something else that could have been damaged when charge pump failed from suspected high pressure during cold start.

My thought on diagnostics would be to install the gauge for checking steering and see what that pressure is. Then with gauge still in steering test port engage the PTO. Does the pressure change? If how much? I significant change would point towards flow loss in PTO circuit and would inspect the solenoid PTO valve. If minimal change then go to next step.

If you have a gauge with capabilities of reading the system 995 PSI I would next leave PTO engaged and then turn steering to lock like testing the system pressure L. If still low pressure then would start by checking valve L which I believe is shown in service manual.

Hope this is written in a manner that makes sense on what first test, second test, etc. is trying to point towards a failing component.

smashedtoe · May 31, 2023

Hello oldnslo.
You ask some great questions and bring up some great points.
I am still waiting for my pressure gauge kit to arrive in the mail and will run the tests you suggest. I will definitely share the info with you. Heck, if I could buy you dinner or a bevvie I would do that too just for being so helpful!
Stay tuned bud...more to come.

smashedtoe · Jun 8, 2023

oldnslo said:
Smashed,
Since the charge circuit is fixed displacement pump we can use the theory that when the pump is turning the oil must go some where and that it will flow to the point of least resistance.

In reviewing the schematic from the service manual it would indicate their four potential flow paths.
1) Across valve O and into the HST for make up oil for leakage losses.
2) Through the PTO circuit. Note: I suspect there should be an orifice in this circuit to control PTO clutch engagement speed but is not shown in schematic.
3) Through valve M to steering. This is where majority of oil would typically since goes through steering unit, then through heat exchanger and back to tank.
4) Across main relief valve L. L would have to be stuck open at pressure lower than M or you would not have any steering.

The service manual shows how to check for steering pressure M, system pressure L. Also shows how to test PTO pressure K. Since steering is not working properly oil is going through another leak point either into the HST, through PTO or something else that could have been damaged when charge pump failed from suspected high pressure during cold start.

My thought on diagnostics would be to install the gauge for checking steering and see what that pressure is. Then with gauge still in steering test port engage the PTO. Does the pressure change? If how much? I significant change would point towards flow loss in PTO circuit and would inspect the solenoid PTO valve. If minimal change then go to next step.

If you have a gauge with capabilities of reading the system 995 PSI I would next leave PTO engaged and then turn steering to lock like testing the system pressure L. If still low pressure then would start by checking valve L which I believe is shown in service manual.

Hope this is written in a manner that makes sense on what first test, second test, etc. is trying to point towards a failing component.

Hi.

Okay, so I put my pressure gauge on to check for the steering pressure M via the steering test port resulting in less than 100PSI (I need a gauge with a smaller range to get exact PSI). When I engage the PTO, pressure jumps up to 350PSI regardless if I am attempting to turn the steering wheel left/right or not. You suggest inspecting the solenoid PTO valve. What exactly does this solenoid valve do?

Another thing I looked into was the system relief valve which appears to be normal and no indication of any debris in the port. What is odd though is the amount of air burping through the system relief valve port and the steering test port when the tractor is running. Almost as if it is sucking air or lacking oil supply?

When I loosen the hydraulic line from the steering cylinder and turn the steering wheel, a combination of air and oil come through. I am starting to get hung up on this air burping through the system and wondering if this is the problem? It would explain the issues I am experiencing. If so, where or how is this air or lack of oil originating?

oldnslo · Jun 9, 2023

In most cases air would be coming from a leak in the inlet or suction side of the pump. Do you recall how the inlet of this pump is routed? Are their O-rings that could have gotten pinched or damaged during assembly? A down tube to the suction screen possibly not tight, etc.

Shaft seals on the pump can also allow air in if damaged.

On certain instances you can get a Venturi effect where oil flowing at velocity can draw air into the system but not real common.

smashedtoe · Jun 13, 2023

There are a total of five o-rings on the charge pump and then an o-ring on the suction line to the sump. I am going to tear the tractor down again and make sure these are all fine as this makes sense. Aside from time, I really have nothing left to lose!