2020 loses hyd.

[Ragnarok]

A friend bought a pretty decent looking JD 2020 with an Allied loader. He serviced the hydraulic filter and changed the trans oil(cheap '303' fluid)...I doubt he checked the trans screen.

Anyhow...after he used it for a few hours after that the hydraulics got weak and quit. I checked it out and seems to me the stroke control valve in the pump may be hanging up when it gets hot. He brought it over to my shop and left it. I got on it a couple days later and drove it around working the loader and three-point and everything worked fine for a bit and then the hydraulics just fizzeled out...loses steering and all high pressure functions(two speed still shifts).

I'm not all that familiar with the little axial piston pumps on these. Can you change the stroke control valve on those little pumps without removing the pump??

Any other ideas about faltering main hydraulics on these little tractors?

Thanx Rag

 

[Tx Jim]

Check trans screen. What type valve controls Allied loader? With 3 pt raised engine running look in open hyd filler hole behind seat for moving oi.

 

[Tech 7]

Fairly likely to be rockshaft valve leak as Tx Jim mentioned. Not a terrible fix

 

[Ragnarok]

Three point works and stays up...but I will check it out.

Loader valve is plumbed direct and returns to the filter housing.

 

[Ragnarok]

Another thing I thought I might check would be the pump drive shaft a key(looked at JD online parts)....I had a 4440 strip the splines from the pump drive shaft last summer....but it lost it all at once and no more until it got a new shaft

 

[Tx Jim]

(quoted from post at 12:26:15 07/15/20)
Three point works and stays up...but I will check it out.

Loader valve is plumbed direct and returns to the filter housing.

Sorry but I didn't ask if 3 pt stayed up, I asked if moving oil could be seen through hyd filler hole with 3 pt raised & engine running??

Another simple diagnostic test is disconnect FEL control valve return hose from tractor,cap tractor fitting & with FEL control lever or levers in neutral then start engine. With engine running no oil should exit open FEL control valve return hose.

 

[Tx Jim]

Does this tractor have continuous or hyd pto? Another simple diagnostic test is disconnect power steering supply line & cap line to frt pump. Power steering o-rings could be faulty.

 

[Ragnarok]

(quoted from post at 11:27:46 07/15/20)
Does this tractor have continuous or hyd pto? Another simple diagnostic test is disconnect power steering supply line & cap line to frt pump. Power steering o-rings could be faulty.

Hmmm...not a hyd. pto has a dual stage clutch and pto shift lever.

I've done those steering column o"rings before!...They are awesome.

I did not mess with the friend's 2020 much today. I did start it up and check to see if the hydraulics were working cold today like they did yesterday...no..had some but weak and jumpy...did have good power steering until I used the three point and worked the loader some...then it all quit again. I did look to see if it was spraying/flowing oil in the fill hole and nothing I thought out of the ordinary.

Maybe something bogus with the priority valve but for some reason I have it in my head it's the pump.

The hydraulics just come and go. Friend bought it in May and it was working fine then. Friend and his friend serviced the tractor and changed filter and oil...still worked ok until his friend borrowed it...then it quit.

I think I'll start the old fashioned way...drain the trans oil snd look tor debris in the screen and filter....I wonder if the filter housing plate stuck to the old filter and got discarded...then it ate some debris and stuck something down the line....just thinking online...I appreciate the help

My first thoughts were that maybe it blew out a trans-pump pipe with the thick 303 oil...but with it working well part time then quitting after some use I'm thinking it's sticking a valve somewhere.

I'll check the loader valve but pretty sure it has the right CC plug in it...

 

[Tx Jim]

If FEL control valve is not at fault my next guess is faulty stroke control valve or possibly hyd filter relief valve is stuck open.

 

[tim s]

You are entering the the world of the Dubuque hydraulic system..The issue is most likely in the middle of the transmission,, the trans/charge oil area..there is a leak in that area and as the oil warms up you are loosing the charge oil,,worn trans pump cracked oil line, worn o-rings...all of these things can contribute to loss of charge oil. Get a schematic of the system and study it like a road map..it will help you begin to search out the issue. Keep in mind that the front pump needs to be fed a constant flow of charge oil..when you loose your pressure remove the charge oil line at the front pump and head it into a bucket,,my guess is the oil going to the bucket will not fill your coffee cup.

 

[Tech 7]

Take the hood off and make a fitting to fit into the reservoir in front of the rad. Install a 60 lb gauge to monitor lube
pressure with the main pump in stroke then out of stroke. A difference of 5 psi or more indicates a high pressure leak

 

[Ragnarok]

Trash on the suction screen....lots of debris probably from a previous issue as it all looked like old stuff.

A closer inspection of the machine shows the left final drive has been off at some point in the past. My guess is that either the planet gears or axel bearings went out(or maybe blew out the diff lock)....it got repaired and nobody ever pulled the screen after that.

I drained the fluid and destroyed the screen getting it and a pound of scrap metal/debris. Flushed the trans and screen hole as much as possible...new filter and screen plus fresh oil and the hydraulics work excellent.

The plan is to run the little green beast until this fall and drain/discard the oil and change the filter/inspect the screen and see what's in it then....

 

[WMcC]

Hello, All!

I'm having similar hydraulic problems with my 2020, so I thought I would try to pick up on this discussion where there appear to be several experts on the topic. I've had this tractor (TYP T5R3C / SER 075265T; 1968 model, I think) about 10 years, and it just recently had a sudden loss of all hydraulics (3-pt, steering, & loader) while I was running a bush hog. Not long after detaching the bush hog (from 3-pt-hitch), the hydraulics suddenly returned. I topped off the fluid level, drove around a bit more, and again it suddenly quit. It's followed the same pattern multiple times nowall there for a bit, then all gone again. Operating temperature doesnt seem to matter. It seems just as likely to change (quit or restart) at any time or temp.

The front hyd pump has always had a chattery noise to it, but that noise seems to increase when the failure is happening. A gentleman at the local JD dealer advised to check the screens and filter first, so, after draining the fluid, I checked the screens to find only slight debris (and no visible filter issues). In any case, I cleaned both screens (little one in pump and longer one in x-case), replaced the filter, and refilled the fluid. That brought no change to the intermittent failures.

The dealer advisor then suggested I start the tractor (while it had no hyd power) let it run a bit, then remove the plug from the top of the little reservoir tank above the front pump, just forward of the radiator. He said the main front pumps rarely fail, so it could be the charge pump back in the transmission case; therefore, low or no fluid in the little tank would indicate that failure. After running that check, I found the little tank to be full to the top.

It looks like other factors were mentioned in this discussion (control valves, relief valves, high pressure leak), but those are Greek to me at the moment. With the behavior Im seeing, would you all have any other suggestions or guidance you could offer before I focus on the main pump?

 

[buickanddeere]

(quoted from post at 11:52:19 10/03/20) Hello, All!

I'm having similar hydraulic problems with my 2020, so I thought I would try to pick up on this discussion where there appear to be several experts on the topic. I've had this tractor (TYP T5R3C / SER 075265T; 1968 model, I think) about 10 years, and it just recently had a sudden loss of all hydraulics (3-pt, steering, & loader) while I was running a bush hog. Not long after detaching the bush hog (from 3-pt-hitch), the hydraulics suddenly returned. I topped off the fluid level, drove around a bit more, and again it suddenly quit. It's followed the same pattern multiple times nowall there for a bit, then all gone again. Operating temperature doesnt seem to matter. It seems just as likely to change (quit or restart) at any time or temp.

The front hyd pump has always had a chattery noise to it, but that noise seems to increase when the failure is happening. A gentleman at the local JD dealer advised to check the screens and filter first, so, after draining the fluid, I checked the screens to find only slight debris (and no visible filter issues). In any case, I cleaned both screens (little one in pump and longer one in x-case), replaced the filter, and refilled the fluid. That brought no change to the intermittent failures.

The dealer advisor then suggested I start the tractor (while it had no hyd power) let it run a bit, then remove the plug from the top of the little reservoir tank above the front pump, just forward of the radiator. He said the main front pumps rarely fail, so it could be the charge pump back in the transmission case; therefore, low or no fluid in the little tank would indicate that failure. After running that check, I found the little tank to be full to the top.

It looks like other factors were mentioned in this discussion (control valves, relief valves, high pressure leak), but those are Greek to me at the moment. With the behavior Im seeing, would you all have any other suggestions or guidance you could offer before I focus on the main pump?

Front pump drive maybe worn to bits . Have a new fan belt handy when working on the pump drive .

 

[WMcC]

Front pump drive maybe worn to bits . Have a new fan belt handy when working on the pump drive .[/quote]

I'm assuming that belt would be because it can only be changed when the shaft is removed, so this would be an opportune time. I never even noticed that! That's a great tip! Thank you!!

 

[WMcC]

While there was no hydraulic function, we were able to check and confirm the correct flow of oil from the little reservoir tank toward the oil cooler (per "transmission oil pump check" in the service and tech manuals). Also, just for kicks, we put a high pressure gauge in the top of the main pump (per pressure control valve check procedure).

With that connected, the functions just happened to start working again, and it read in the normal stand-by range (2200-2300psi). Then, interestingly, when the functions eventually quit again, the pressure dropped only to about 1500psi (and the gauge line pulsated in sync with the chatter sound from the pump). This just happens to be exact pressure the manual says should be set by the [i:5db43bc71e]stroke[/i:5db43bc71e] control valve (via screw on bottom of pump) when testing the pressure control valve, and functions should NOT operate if the pressure control valve is correct.

So, I'm now wondering, is it possible that ONLY the stroke control valve inside the main pump is failing somehow? Would that even be possible? Could it intermittently fail to a de-stroked state? Has anyone ever heard of that?

 

[Tx Jim]

Yes stroke control valve can have a faulty seating area or foreign object stopping stroke control valve from seating properly

 

[WMcC]

Thanks, Jim! I finally got the stroke valve out of the pump. It has a seat that fits very snug and to the end of the valve chamber. Before removal, it was oriented as shown in Pic1, with a deep "female" bevel cut facing up and away from what appears to be the corresponding "male" bevel on the nose of the valve. I'm curious if it's possible the seat should be turned the other way, as shown in Pic2, where the very shallow "female" bevel cut is facing up instead.

The service manual (shown in pic backgrounds) doesn't show the seat with enough detail to make the orientation of the bevels clear. If someone had no idea how it was to be assembled, is there a more detailed spec that would show that?

[/img:bebd21b08f]