Jd401D lost hydraulics after using manual destroker

[Nickaballison]

I have a 401D that was working great 2 weeks ago when I parked it before a cold front. Tried starting the tractor at the end of the cold front at about 25 degrees outside. It was struggling to start so I drove down the manual destoker as the manual suggested for cold weather starting. It still wouldnt start. I left the destoker in and finally got it to start today in 60 degree weather. I promptly pulled the destoker back to the normal operating position and now I have no bucket hydraulics. I found the dipstick by the seat low on oil so I filled it up. transmission moves forward and reverse fine. Steering is difficult. Any suggestions on what to do, what I may have done wrong? Thanks

 

[Tx Jim]

Welcome to YT
With engine operating screw destroking screw CW a few turns then turn CCW back to original location. Hopefully a small piece of foreign material was keeping stroke control valve from seating & this technique will let foreign material move on & hyd's will operate correctly. If not report back & maybe another member can help you.

 

[Roy Suomi]

When you turn that tee handle down, you shouldn't turn it in all the way down till it stops. It only has to go to the point of resistance then
another half to three quarter turn to destroke that pump. Something has gotten stuck inside the pump front cover. I would loosen the tee handle
so no tension is felt on it and walk away from it for a day or so. Maybe the valve will unstick itself by having no tension on it. If it doesn't
work, you will need to remove that front cover and physically free it up by hand. You will need another cover o-ring and watch none of the check
valves fall out. watch out for shims for that shaft bearing preload. Once you get it working unscrew the tee handle all the way up to seal oil
leakage from the tee.

 

[Nickaballison]

So I already tried that this morning with no success but I figured what the heck Id try it again. Nothing happened with first try, did it again and sure enough bucked started moving, however slower than Id ever imagined possible. I did it a third time and it started moving at normal rate. I have it on the schedule for hydraulic and transmission fluid and filter changes when it gets warm. I did notice after the third attempt at opening destroker there is a pretty decent leak around the bolt now. I am wondering if it is possible to just change out the manual destroker assembly or would an entire pump rebuild be required? Thanks again for your suggestions.

 

[fdt860]

(quoted from post at 15:36:27 03/14/22) So I already tried that this morning with no success but I figured what the heck Id try it again. Nothing happened with first try, did it again and sure enough bucked started moving, however slower than Id ever imagined possible. I did it a third time and it started moving at normal rate. I have it on the schedule for hydraulic and transmission fluid and filter changes when it gets warm. I did notice after the third attempt at opening destroker there is a pretty decent leak around the bolt now. I am wondering if it is possible to just change out the manual destroker assembly or would an entire pump rebuild be required? Thanks again for your suggestions.

The manual destroker seals without seal, by tightening it counterclockwise. If it is loose, it leaks.
It is possible to change it with money, but using it properly should be fine. My guess is that it needs some pbblaster, then it will work fine.

 

[grwrench]

hello,, if you take the destroke valve out.. most use a 11/16 wrench.. you can take the assy. apart & replace the oring. it would be handy to have a plug to stop oil spill while you have it
out..

 

[Tx Jim]

Nick
Thanks for update & it's nice you have tractor hyd's operating again.

 

[tim s]

This is why I think jiggling the steering wheel is better than fiddling with a de-stroke valve screw...and many times the Manuel de-stroke screw will loosen and hold the stroke valve open..

 

[Nickaballison]

I am new to tractors and have not studied the hydraulics circuit much yet. What does turning the steering wheel do thats similar to the destroker? Is that just dumping fluid on the high pressure side of the pump so the pump is under less pressure therefore allowing engine to crank quicker?

 

[Tx Jim]

(quoted from post at 09:21:58 03/15/22) I am new to tractors and have not studied the hydraulics circuit much yet. What does turning the steering wheel do thats similar to the destroker? Is that just dumping fluid on the high pressure side of the pump so the pump is under less pressure therefore allowing engine to crank quicker?

Yes turning steering wheel rapidly from side to side relieving trapped pressure causes hyd pump shaft & engine crankshaft to be easier to rotate by starter

 

[Roy Suomi]

Just open the tee handle all the way and it will seal on an internal seat in that cap the tee handle protrudes from.

 

[WTW]

The two ways discussed are both reducing cranking load from starter but, doing two complete different things concerning function of pump. Wiggling steering wheel does not shut pump off like the de-stroking screw does. Wiggling steering wheel just reduces pump working pressure leaving pump still pumping at a cranking RPM. You could say you are creating a huge pump leak to exhaust pump flow at this cranking RPM.
The de-stroking screw physically holds the stroke control valve open allowing pump to shut itself off by directing pump output flow / pressure into crankcase of pump holding pumping piston out / away from pump shaft lobe. This function de-strokes pump. Pistons do not actuate as they are held out so the cannot contact pump shaft lobe inside of pump.