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JD 300 hydraulic rebuild advice?

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Gator

06-25-2003 11:07:07




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Have been given a JD 300 which has a very leaky forward PS hydraulic pump tied into the rear 3 point pump which has apparently failed. The hacked system still operates both, but only marginally. Is there a cost effective way to rebuild both and remove the hack or is it cost prohibitive? Tractor runs strong otherwise.
Thanks for any input and leads to parts. Gator




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davidval

06-29-2003 05:54:38




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 Re: JD 300 hydraulic rebuild advice? in reply to Gator, 06-25-2003 11:07:07  
the priority valve (pressure control valve at the pc) is at the end of the pressure line that the gate valve is connected to(acc. to the description)
the system is closed center, which means there is no flow in the system unless a hydraulic consumer is activated.
from your description there is a major internal leak in the system. first thing to do is to remove the adaptor in front of the priority valve and see if there is a spool there. also there should be a valve in the middle of the spool. look at the pc.
david

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jdemaris

06-25-2003 19:32:36




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 Re: JD 300 hydraulic rebuild advice? in reply to Gator, 06-25-2003 11:07:07  
I don't understand your description of the system or problem. Older 300 industrial tractors have an 8 piston front mounted main hydraulic pump that is fed by a small charge-pump inside the transmission and a separate power steering pump mounted on the front of the engine. Later models did away with the separate power steering pump and used main system hydraulic oil teed into a priority valve.



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John

06-25-2003 18:01:53




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 Re: JD 300 hydraulic rebuild advice? in reply to Gator, 06-25-2003 11:07:07  
Your description is confusing. Can you repost and describe the hydraulic pump setup in a bit more detail?



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Gator

06-26-2003 07:45:43




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 Re: Re: JD 300 hydraulic rebuild advice? in reply to John, 06-25-2003 18:01:53  
Please forgive my poor description. I'm certainly no hydraulic expert and very much appriciate your response/help to my mystery.
I assumed there had been a failure of a secondary pump for the system which is why the previous owner had seemingly tied a manual gate valve/diverter into the system. It was spliced with high pressure rubber lines into the line running to the power steering box at the base of the steering coloume and teed off toward the transmission box from there. Rotating this gate valve regulates the amount of hydraulic volume shared by the three point hitch or to the power steering. On a heavy lift for the hitch almost a full diversion of the pressure will almost disable the power steering. After reading jdemaris response it looks like there may be only one (very leaky) main pump bolted directly to the front crank pully shaft. Could this be a way to work around a failed priority valve? Where can I get parts for this problem?
I have a rather poor photo I took last night but am not familiar with how to attatch it for this forum. I posted it in the photo gallery under JD 300. you can almost make out the valve handle on the side under JD 300 sticker.
Hope this whole post is a little more understandable.
Thanks again. Gator

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John

06-26-2003 15:07:50




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 Re: Re: Re: JD 300 hydraulic rebuild advice? in reply to Gator, 06-26-2003 07:45:43  
Sounds like the priority valve was bypassed for some reason. I would suggest plumbing a pressure gauge somewhere and make sure the main pump is putting out 2250 lbs first. Is the priority valve body still there?



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Gator

06-26-2003 19:18:50




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 Re: Re: Re: Re: JD 300 hydraulic rebuild advice? in reply to John, 06-26-2003 15:07:50  
Need to look through my parts manual to even find where it is and then to find and plumb a gauge that will read 2200 lbs. Can a new priority valve be so hard to find or replace that all the effort was put in to bypass it? Any clues on the difficulty/cost in rebuilding the pump and replacing the valve?
Thanks for everyones help. Gator



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