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| 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. | |
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John Deere 4020 hydraulic problem
