John Deere 2140

[bgmillar]

Hi There,
I have a John Deere 2140 that front end loader works fine as does rear mounted post driver but frequently the rockshaft (lift arms) will not lift the post driver at all but occasionally I can get it to lift by activating the loader or post driver controls! I have replaced oil, main filter, checked screen adjacent to main filter and all fine. Any helpful suggestions would be appreciated. Thanks. Barrie.

 

[Tx Jim]

Sounds as if post driver valve and possibly ind loader valve(if equipped) are open-center instead of closed center. Also with 3pt lever in raised position with engine running,look inside hyd filler hole with a light for "spraying oil".

 

[bgmillar]

Preiously looked in filler hole for squirting oil but looked ok with only odd dripping happening. I assume valve setup to be ok as I have been using machine (over several months) and have whacked in about 100 posts but occasionally it just wont lift without raising/lowering loader (which works 100% of the time) but from timr to time it wont lift even doing that yet the post driver controls still work! Is there something in the rockshaft housing which may cause this I wonder Jim?

 

[Tx Jim]

Disconnect return hose from tractor to loader valve,aim hose in a 5 gal bucket or hyd filler hole,with both hyd valve levers in neutral start engine and if oil flows out of return hose the loader control valve is open-center and the problem.

 

[bgmillar]

Today I started tractor with hose into bucket but was only a very minor flow (about 1 cup over 4 - 5 minutes) and then checked in refiller hole but certainly no spray evident at all. What surprised me tho was that everything worked perfectly and raised postdriver about 15 times no trouble so this confirms that the fault is certainly intermittent. I have previously had the problem at end of day and went and tried it first thing next morning when all was cold and it still didnt lift then. I cant trace any info on hydraulic circuitry that operates the rockshaft so am in the dark about valves etc that may be the cause of my problem.

 

[Tx Jim]

Sometimes the stroke control valve in main hyd pump can get worn and hang up a bit. You might consider replaced stroke control valve. How many hours are on the tachometer? Parts key # 20 are the control valves for rockshaft. Where is lever(parts key #1 in 2nd schematic setting)? If not in "D" put it in "D"

 

[bgmillar]

Hi Jim, At a mechanics suggestion I replaced the main pump load control valve although I did not replace the seat as that requires removal of pump to press out and in the new one. The valve showed where it was contacting seat but did not think it was significant and it did not affect my problem.
My machine does not have an hour meter as part of the rev counter but best estimate is its 1985-87 vintage and has seen many hours in the field!
I assume you mean D is the lower position available which is Depth Control?

 

[Tx Jim]

Yes "D" stands for depth. IMHO replacing SC valve without R&R of seat is similar to overhauling an engine and re-using old rod brgs.

 

[bgmillar]

Yes Jim I agree that not replacing seat perhaps is not the smartest decision I ever made but as I said at the time removing pump was a bigger issue than I was prepared to tackle but may revisit the idea after your comment! The fact that the other services operate normally at times when rockshaft will not raise - could that preclude the SC Valve contributing to the problem I wonder? Or does the rockshaft cylinder use a much smaller amount of fluid and hence not lift SC Valve off its seat 100% of the time?

 

[Tx Jim]

Have you checked stand-by pressure with a gauge??? It needs to be 2250-2350 psi. Yes I think RS piston would require less hyd oil to operate than loader or PD.

 

[bgmillar]

No I havent checked any pressures as I dont have gauges/flowmeter equipment at all unfortunately. Should I find a gauge from somewhere does it fit onto pump above SCV where a destroking valve would fit?

 

[Tx Jim]

Simplest/easiest way to check stand-by pressure is install male coupling on gauge and install in rear breakaway coupler of SCV.

 

[bgmillar]

Thanks Jim. I will try to find a gauge to buy in next few days and I guess even loader quick coupling will suffice for checking pressure only.

 

[bgmillar]

Have you checked stand-by pressure with a gauge??? It needs to be 2250-2350 psi. Yes I think RS piston would require less hyd oil to operate than loader or PD.

Hi Jim,
Got a gauge and shows pressure around 2500. Also I managed to drive out SCV seat but was a mission as on startup there was no pressure at all! On removal of seat realised it was several mm longer than original and had different angle as well. Decided to reinstall original seat and got pressure back again!
Used tractor today to thump in some more posts and had same old problem where rockshaft would not lift post driver 90% of times and to get it to raise - lifted loader and then it would raise but sometimes I would need to actuate loader 10 - 15 times to achieve. The other symptom is that driver will only lift about half way most times but occaisionally will lift to full height. This certainly is a puzzle to me being intermittent like this.

Barrie

 

[vtsnowedin]

Years ago I had a David Brown that acted similar. There were two spool valves in the rear end housing to the right of the drivers seat. You could access them by removing a cover and unscrewing the top caps off each being careful to not let the cover or spring under it pop up and then down into the rear end housing (yah that's how I know that one).:ashamed: Once the cover was off and the spring recovered you could slip the spool up out of its seat and flush off the bit if grit that had got stuck between the spool and the close tolerance hole it fits into. This bit of grit or metal was what was catching the spool in the part open position and causing the problem. Something 1/10,000 inch was all it took and could be a bit of dirt that washed down the shift lever past a worn boot and into the rear end that served as the hydraulic reservoir. Maybe something along that line is your trouble?

 

[Tx Jim]

bgmillar
By chance have you checked the post driver control valve similar to the way you checked the loader control to ascertain if the valve is open or closed center. PS:2500 stand-by is too high. I'd lower it a little.

 

[bgmillar]

bgmillar
By chance have you checked the post driver control valve similar to the way you checked the loader control to ascertain if the valve is open or closed center. PS:2500 stand-by is too high. I'd lower it a little.

No I haven't checked the PD control and will do that in next couple of days and also lower pressure a tad too!
I do recall disconnecting the quick disconnect couplings to the PD initially when the problem first surfaced but it didnt make any difference at all, but will check it out as suggested.

 

[bgmillar]

Years ago I had a David Brown that acted similar. There were two spool valves in the rear end housing to the right of the drivers seat. You could access them by removing a cover and unscrewing the top caps off each being careful to not let the cover or spring under it pop up and then down into the rear end housing (yah that's how I know that one).:ashamed: Once the cover was off and the spring recovered you could slip the spool up out of its seat and flush off the bit if grit that had got stuck between the spool and the close tolerance hole it fits into. This bit of grit or metal was what was catching the spool in the part open position and causing the problem. Something 1/10,000 inch was all it took and could be a bit of dirt that washed down the shift lever past a worn boot and into the rear end that served as the hydraulic reservoir. Maybe something along that line is your trouble?

It wouldn't surprise me it was something similar but am reluctant to delve into this territory as yet as it is quite a mission to get into that area but thanks for the thought.

Barrie

 

[bgmillar]

Hi Jim,
Checked the post driver today as you suggested but no flow at all from the return hose.
I think next step would be to lift rockshaft housing off and give everything there a going over.
I have an unrelated question - I would like to replace the diff lock operating lever (which was broken in half just above foot pedal attachment point when I purchased tractor) but it looks like it wont come off its shaft without access into the internal workings of the back end. Is it possible that lifting off rockshaft cover will enable access to replace the lever?

 

[Tx Jim]

From parts catalog photo that appears to not be that difficult especially after removal of rockshaft housing. Since everything's been changed I don't have a slightest clue how to download a photo.