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Re: IH 784 Hydralics went from strong to weak overnight.

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Ben MacLeod

12-10-2013 04:39:59

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@mstas: I removed the filter and this screen for diagnostic purposes and there was no discernible difference in performance. Filter and screen ruled out.

@thefarmhand: All o-rings that are in or around the MCV have been replaced and all still look ok.

@JimB2: I don't know how this valve works, but it seems to me that if it were malfunctioning, I would lose steering pressure while lifting the loader but is it also possible I would lose pressure everywhere? When the pump got weak initially, I always still had steering and the loader would still go all the way up and down just off idle. It just didn't have any lifting power. Now, no hydraulics will work at all between Idle and at least half throttle. No steering, no 3pt hitch, no loader, no aux... the pto is good and strong though I have no idea how this is engaged.

@Harold Evans: The only way I know to bleed the air is to remove the flow divider valve and start the tractor until fluid flows continuously. Which I have done... is there more to it?



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John Vetick

12-10-2013 05:46:28

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 Re: IH 784 Hydralics went from strong to weak overnight. in reply to Ben MacLeod, 12-10-2013 04:39:59  
Ben, first, I'm in my late fifties, currently disabled but still work a little on tractors. I currently serve as director/advisor to the technical college in my area in the diesel and ag mechanic's dept's. So on that, I was service manager at an IH/CaseIH dealership for fifteen years so, I do have a lot of experience in these. Your problem is not strange but, I need a lot more information first. Is the tractor making a howling noise? Does the hyd oil, if you run it into a bucket from the couplers foamy or a solid stream without any foam? Next, you said you replaced all the gaskets and o-rings on the SCV, right? What about the pump? I was reading your problems and got mixed information as the SCV regulates flows and pressures. The main thing I was wondering is it the rear hyd, "three point and aux hyd" or is all hyd, which is the steering brakes, etc? If you want to talk more, just email me your answers. I can help out on this but, need more info. to analyze. Thanks, and good luck. my email is if you want to contact direct.

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12-10-2013 17:41:17

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 Re: IH 784 Hydralics went from strong to weak overnight. in reply to John Vetick, 12-10-2013 05:46:28  
Ben, the PTO is engaged by a spool valve covered by a rubber boot on upper right of MCV.

Reference 784 MCV parts diagram.
1)Bottom left front Items 4-12is Power Steering, Oil Cooler, Power Brakes outlet and relief valve at 1500 PSI, item 1-3, 13 are priority valve that diverts 3 GPM to PS,PB and Oil Cooler.
2) Item 39-42 is main relief valve at 2500 PSI
3) Items at top right are to do with PTO.
Not shown is 3PT pressure and return connecting on back right.

I still believe that somewhere the Hytran is bypassing the pressure lines to the PS,PB and 3PT and wherever the bypass/leak is by reving the engine there is enough flow to operate the PS, PB and 3PT at reduced capacity.


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Ben MacLeod

12-26-2013 18:45:54

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 Re: IH 784 Hydralics went from strong to weak overnight. in reply to JimB2, 12-10-2013 17:41:17  
Just fixed this today. Oil seal was blown out of my new pump. (the seal keeper was pinched from the factory).

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