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656 Hydraulic pump whine


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#1 redrooster1466

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Posted 08 June 2010 - 10:25 AM

Just bought a 656 with a 2250 loader, and the rearend is full of oil, but the tractor makes a loud whining from the hydraulics all the time, it doesnt change when you move the bucket or anything and the hydraulics work great. It is a very loud whine and if you feel the two lines coming off the plate the pump is bolted to that go to the valves and the hitch, you can feel a good vibration in them. I changed the filter yesterday and it didnt change anything, so I tore the pump apart and the larger of the two pumps shows some wear and a couple cavitation spots, and the small pump looks fine, and all the seals and o-rings look fine. Any ideas or thoughts would be appreciated. Thanks

#2 Ernest

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Posted 08 June 2010 - 11:27 AM

My first guess would be you are getting air somewhere or you got moisture in your oil. We tested out a 656 2 years ago that the oil looked fine but when we started the tractor up and ran it some the oil got milky and you could see some leaking from various hydraulic lines and it was whiny also! Or like you noticed the cavitation is causing it also!

#3 harvester66

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Posted 08 June 2010 - 09:07 PM

Two things you need to check first since pump is out replace suction tube between pump and filter housing it has a seal pressed on outside of it, this fixed my 656. the other thing to check there is a rubber hose in rearend on the suction tube you can check this by removing 3rd link cover good luck.

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#4 pete 23

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Posted 08 June 2010 - 09:20 PM

Good advice from both posters. Another thing that comes into play is all the different pump configerations the 656 used. The twelve gallon was on first production. Then 17 gal pump with reduced pump rpm to still attain 12 gal. So, if someone put in an increased capacity pump in the original production tractor you are pulling too much oil through the filter and you will have more cavitation problems. There is a larger filter and cover available and is actually good for even the smaller pump as there is just too much flow through that small filter. The hitch pump is likewise changable from 7 to 9 gal and adds to problem.

#5 Jim J

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Posted 08 June 2010 - 10:02 PM

The problem with the 656 hydraulic system is that it is a captive air system. Any air that get into the system is returned trough the return has and is sent straight to the pump for an other trip around the hydraulic system. I have been cutting the return hose below the oil level and plugging the end that goes to the suction tube. It makes a world of difference on how much cavitation the pump has. I haven't seen any shorter pump life.



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