John Deere 2020 Hydraulic Questions

   / John Deere 2020 Hydraulic Questions #1  

airrj

Member
Joined
Mar 6, 2012
Messages
28
Location
Cheyenne
Tractor
CK45
I am working on a JD 2020 with a hydraulic issue. The loader and 3-point have chatter in them and after 3 or so lifts there hydraulic system will no longer lift the loader. Wait a few minutes and you can get a few more lift, and so on, and so on. The tractor I believe is a 1966 Type T5H3C; SN 018900T with a JD146 loader. It has 4204 hours on it.

I have drained the fluid and checked the filter and the inlet screen. Both have a reasonable amount of particulate. I have inspected the suction lines to the main hydraulic pump and I cannot find any cracks in them, as I have heard that this is a common problem.

I am waiting for John Deere fluid and a filter to be delivered tonight. I plan to reassemble tomorrow and test the system.

I have a few questions in advance in case I have more problems.

1. If I need to get a service manual for this tractor, is the I+T manual an acceptable manual, or should I splurge and purchase the factory manual?

2. Are there any inlet screens or filters that I should be looking for before I reassemble?

3. Am I correct that the transmission pump supplies the fluid to the main pump at the front of the engine through 2 suction lines? One line goes from the transmission sump to the main pump, and the other goes from the transmission sump to the cooler adjacent to the radiator and then to the gravity feed hydraulic tank then to the main pump.

If things don't go well tomorrow, I am sure that I will have more questions to follow.

Thanks in advance for your help.
R.J.
 
   / John Deere 2020 Hydraulic Questions #2  
When I had intermittent loader functions I found the crud in the oil had collected in the control valve blocking fluid flow. A tear down of the control valve and a good cleaning cured the problem.
 
   / John Deere 2020 Hydraulic Questions #3  
1) Splurge for the factory manual. No comparison in the two.
2) Besides the sump screen, there is a screen in the pump as well. Depending on which pump you have, it is located in 2 different spots. Most often there is a plug on right side of pump. Plug bore is horizontal at top of pump original pump had a 1 1/4" plug, replacement pump has a 7/8" plug.
3) You are correct. Transmission pump supplies main pump with oil. If there is lack of oil supplied to pump, you could have internal leak in transmission(broken oil lines, leaky clutch pack in hi-lo or independent pto clutch if equipped, leaky filter relief valve, worn trans pump) If there is enough flow to main pump, there may be an internal leak in steering valve, rockshaft valve, or scv.
 
   / John Deere 2020 Hydraulic Questions
  • Thread Starter
#4  
jd110,

Is this the location of the filter in the pump?

IMG_7205a.jpg

And thanks for the list of possibilities. I will report back with my findings tomorrow.

davesl708,

With the problem showing up in the loader and the 3-pt I am thinking that it is more of a systematic problem, but I will keep your suggestion on the list and keep and eye out for that. Thanks.
 
   / John Deere 2020 Hydraulic Questions #5  
The transmission pump after it has supplied loads, demands and lubrication inside the transmission . Any oil left over that can lift the 165 psi or so relief/bypass valve and flows up to the front pump inlet. Any oil the front pump pump does not use , passes on through to the oil cooler and storage tank is so equipped. When the tank and oil cooler is full. The excess oil flows from the tank back to the transmission sump. The 3rd line carries high pressure oil back to the rockshaft and SCV valve.
The tank and cooler are supposed to hold a gallon of two that is supposed to flow "backwards " to the front pump inlet. If the rear pump can not keep up with momentary high flow demands.
When using a loader, backhoe, logsplitter hydraulic motor etc. The return oil must flow into an optional ported transmission filter cover. This will prevent front pump starvation.
If somebody has plugged the loaded into the SCV's instead of a direct supply and ported filter return then using a joystick boom and bucket valves. The loader will never operate properly.
As previously stated. If the transmission pump is weak, transmission screen or filter plugged , a librication priority diversion valve stuck open , failed clutch pack seals or a busted line/fitting. There won't be enough "surplus" oil pushed up to the front pump inlet.

Later tractors supply power steering oil through a priority valve prior to the SCV and rockshaft.
 
   / John Deere 2020 Hydraulic Questions
  • Thread Starter
#6  
Success. A fluid and filter change got everything up and running. The hydraulic oil had allot of non-metallic particulate in it, and the filter when I cut it apart have a good coating of the same particulate on it. The filter had a manufacture date of 2012, so my working theory is that the fluid and filter was changed a few years ago, and then refilled with standard hydraulic oil instead of oil meeting the J20C specification. I believe the particulate is clutch and brake material. The sump screen and the screen in the pump both had some contamination, but nothing too significant.

When the tractor came in the loader and 3 pt would chatter every time they were lifted. And after 3 lifts of the loader there wasn't enough pressure left to lift anymore. Now with the new fluid and filter I could make 10 full lifts of the loader in rapid succession and all 10 took 16 seconds with no slowdown.

buickanddeere, thanks for the additional description, it helps allot. This is my first JD that I have worked on, and my hydraulic experience if from large machine tools not tractors. So without a schematic it is nice to have some additional information. And yes, the loader is plumbed correctly based on your description.

I plan to watch the performance of the loader in the next few months, and I am going to recommend to the owner that we drop the filter in 6 months and cut it open and inspect. If everything continues to behave we will leave well enough alone.

Thanks again for all of your help. I will see if we can get a JD manual before the next problem.

R.J.
 
   / John Deere 2020 Hydraulic Questions #7  
jd110,

Is this the location of the filter in the pump?

View attachment 457300

And thanks for the list of possibilities. I will report back with my findings tomorrow.

davesl708,

With the problem showing up in the loader and the 3-pt I am thinking that it is more of a systematic problem, but I will keep your suggestion on the list and keep and eye out for that. Thanks.
Sorry I haven't been back on, but yes that is the location of the screen in the pump. You remove the plug and then there is a rubber seal that needs to come out to get to the screen.
 
   / John Deere 2020 Hydraulic Questions #8  
Glen
YOU are the person not I that stated there was a ''relief valve that required 165 psi to open" before frt hyd pump could receive hyd oil supply. IMHO the "burden of proof" is on your shoulders not MINE!!!! Continue your normal SMOKE SCREEN when you make an incorrect statement.
Jim:thumbdown:

I don't want to get between you two bantering back and forth, BUT, I think this is the valve buickanddeere was referring to. It is the pressure control valve for the hi-lo adn independent pto. And yes the pump does have to build between 140 and 160 psi to supply engagement pressure for these options before any oil flows to main pump. Key 29 is the pressure regulating valve. If tractor has no independent pto, hi-lo, or reverser, there is no pressure regulating valve. RP1014_________UN01JAN94.gif
 
   / John Deere 2020 Hydraulic Questions #9  
Thread pruned. Send each other a PM, shake hands, and move along please. :cool:
 
   / John Deere 2020 Hydraulic Questions #10  
Hi Airrj, I've done thousands of hours in the JD 20 & 21 series, great tractors and I've had only two problems ever. I too, experienced a hydraulic filter blockage issue with a 21 series(very similar system, if not identical) and it turned out to be metal from the brakes, and (after flushing the system out and new filter)it kept on re-blocking the filter. It transpired that the the early JD brake disks had a pad glued to one side, and the other side had a free floating brake pad(shaped like a disc) Problem was that when the pads got thin the free floating one disintegrated, and ended up in filter.
I replaced both brake discs with the later model brake disc that had the pad bonded to both sides. It fixed the problem.
I'm not suggesting this was your problem, but just a heads up should the filter blockages continue. My mechanic guess incorrectly at the time and had split the gearbox, but nothing was wrong in there, it was only when, on a hunch, I pulled the most used brake apart that I discovered the problem.
 
 
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