|
|
| Have a John Deere 4020 with syncro range, transmission , when you hold clutch pedal in to shift gears you lose power steering, when you let clutch pedal out you get power steering back , what would cause this, where is it losing the pressure at. Thanks for any help. |
|
| |
|
NCIA | It's a common problem in the syncros. Ours did it till we modified it. Has to do with the tank resivoir by radiator that's designed to hold pressure while you hold clutch in. Some kind of spring mechanism in there to help to hold pressure or something like that I'm not sure just what I've heard. Im no expert someone on here can tell you more. |
|
| |
|
| Hopefully Gerald J. will chime in and further describe the issues and what tractors this covers. (pre side console) and any other pertinent details. http://talk.newagtalk.com/forums/thread-view.asp?tid=438400&posts=1#M3528181 I had his page bookmarked as similar issues have been inquired about before. http://www.geraldj.networkiowa.com/4020si.htm |
|
| |
|
| The service information in my web page is a quick solution. I know it works. I did it to my '68 4020 and I have let it set for several months, pushed in the clutch started it and lifted the loader and steered lock to lock before letting the transmission pump turn. I know many others have used that information to make successful fixes. It converts an elbow to a check valve to replace the worn check valve that is deep in the transmission and hard to get to. Side console 4020 moved that check valve up high so if it leaks it doesn't drain the front cooler/reservoir. I have found some bulletins about side console but haven't added them to my web page yet. I plan to do that, I already have them scanned just have to work on the page.
Gerald J. |
|
| |
|
Fruita CO | It shouldn't do that in the time it takes to shift gears-all syncro's will do that, the trans pump stops when the clutch is disengaged. If it quits that soon, you have:
1-trans pump is worn out.
2-A line or o-ring is blown off the pump, or other leak in the low-pressure circuit.
3-High-pressure leak to sump in steering, brakes, rockshaft or SCV. If it's a side console tractor it can be in the PTO valve.
4-Plate on the bottom of the rockshaft housing is cracked or loose.
5-possibly an internal leak in the main pump, but not likely. |
|
| |
|
NCIA | Gerald for what it's worth ours was a side counsel and did it. Do you know if there is any thing that goes bad in the front reservoir tank? Fixed ours by adding a small belt driven pump on the front and running lines back to the rear end and to that front tank. Works great maybe not NAT approved though. |
|
| |
|
| On a normal 4020 they will do that if clutch is depressed for probably 20 seconds as the pump disengages when clutch is depressed.To do between shifts will mean pump problems. |
|
| |
|
Fruita CO | 20 seconds is not normal. If the system is right, it should take at least a minute for things to quit, unless you're running a loader up & down. |
|
| |
|
Fruita CO | The easiest way to find a high-pressure leak is to start it up cold & feel the hyd. components & the return lines off of them. A valve with a leak will start to get warm in a few minutes. Sometimes you can hear a squealing sound in the valve, most noticeable when you shut it off. If the main pump has a destroking screw, turn it in & listen for the engine to unload. A high-pressure leak will cause the pump to stay in stroke & load the engine.
Diff. lock valve can be the problem too...if you suspect a component, you can cap off the pressure line to it & see if it makes a difference.
Edited by ronm 12/23/2014 07:42
|
|
| |
|
| For ordinary hydraulic cylinder operations it should run for hours with the clutch pedal pushed. All the front reservoir needs to supply is the difference in the cylinder volume on the two sides, so when extending it takes oil from the reservoir, but when retracting it puts oil back in the reservoir UNLESS the valve return is plumbed to the transmission sump instead of the return to the SCV or the transmission oil filter. The front reservoir has several gallons of oil stored at about 250 psi,. On the early new generation tractors returning oil to the transmission case means the available flow is limited by the charge pump, which is smaller than the main pump, not the flow of the main pump. That's not the right way to use the tractor hydraulics.
Gerald J. |
|
| |
|
| What I had noticed in the service bulletin collection I have from looking a few years ago was that there's a bulletin that I didn't have that from the index hinted in a side console tractor the most common cause of loss of pressure was a high pressure leak in the high pressure line or in any of the valves from SCV, three point rock shaft, differential lock, brake or steering and since several of those valves are cam operated poppet valves, valve or valve seat wear or misadjustment of the valve stem clearance can cause leaks from pressure to return. A couple weeks ago while looking for a bulletin to back up my assertion on not using side console diesel engine pars in a preconsole engine rebuild I found two or three more detailed bulletins on loss of hydraulics in side console tractors. I have scanned them to add to my web page, but haven't gotten around to updating the page yet. it will be the same link as posted yesterday, just will have more information when I get it updated.
As I understand it there is a check valve between the transmission pump and the front reservoir, but its located near the reservoir and above the reservoir (cooler) so when the check valve wears out it doesn't drain the reservoir I don't have that shop manual or parts catalog to check. They are distinctly different between the two major versions of the 4020.
In the pre side console tractors the check valve was at the charge pump in the bottom of the transmission so when it leaks it drains the reservoir. The cure was to convert an elbow into a check valve using Deere parts from some other machine and it works great.
Gerald J. |
|
| |
|
Fruita CO | Gerald J. - 12/23/2014 07:58
For ordinary hydraulic cylinder operations it should run for hours with the clutch pedal pushed. All the front reservoir needs to supply is the difference in the cylinder volume on the two sides, so when extending it takes oil from the reservoir, but when retracting it puts oil back in the reservoir UNLESS the valve return is plumbed to the transmission sump instead of the return to the SCV or the transmission oil filter. The front reservoir has several gallons of oil stored at about 250 psi,. On the early new generation tractors returning oil to the transmission case means the available flow is limited by the charge pump, which is smaller than the main pump, not the flow of the main pump. That's not the right way to use the tractor hydraulics.
Gerald J.
Sorry, Gerald, but hours just ain't gonna happen, especially now, as old as these tractors are...internal leakage will make it use up the reservoir in a while. 5, maybe 10 min. is a pretty good system in the real world.
The reservoir & cooler hold maybe 2 gal., & it's at 100 PSI max, that's what the cooler relief pops at. Actually it's free flow back to sump from the cooler if the main pump doesn't use it...
Other than that, good description! |
|
| |
|
| Well when I got to editing the web page I found two of the three and the one new one was the one in the index that I hadn't found before. Seems the service bulletins aren't exactly in numeric order in the binder. I need to correct that for future searches.
The newly found bulletin shows some potentially sticking valves that could be a cause of hydraulic loss in side console tractors. The other two bulletins show some test techniques for identifying a leak problem and finding that leak, probably a valve. One test heats the oil and checks for pressure and if pressure can't stay up 5 minutes says there is a leak to be found and fixed. The other prescribes plumbing changes at the cooler and reservoir which apparently in the side console tractor are separate pieces of hardware. The T69-3, T70-10, and T71-2-3 on the tops of the pages show the two digit year and month of each bulletin which I have posted in chronological order.
http://www.geraldj.networkiowa.com/4020si.html
Gerald J. |
|
| |
John Deere 4020 hydraulic problem
