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Farmall 656 Hydraulics


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#1 k1128

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Posted 16 April 2011 - 05:59 AM

I am new here and looking for anyone who ran into this problem on a Farmall 656 before and any possible fixes.

I have power to my steering and power to my 3 point but no pressure to my auxiliary lines (have low flow, just not enough pressure to lift my loader).

Background (this will be long so I apologize in advance)I just wnat to get all the details in order to help find the problem.

About 2 weeks ago, I dug a hole with the loader to bury one of our mini-horses. Digging was hard so I had to keep RPMS up and air in the loader lines was obvious and got progressively worse as I dug. When I was done I still had aux power to the loader albeit sluggish. Two days later, I went to move the 656 and had NO aux power so I couldn't lift the bucket. It would wiggle just a little but you had to really look to see it happen.

I had been sucking air for ahwile but couldn't find the issue, overfilled by 5 gallons and problem became minimized so we kept using the loader as needed (once or twice a month). After I had no aux power I did some research and heard about the suction rubber hose in the rear diff, checked it and of course it was split at the top. I replaced the hose, changed fluid and filter and started the tractor up. The air seemed to be gone but I still didnt have aux hyd.

While bleeding the system (moving wheeels back and forth like manual says) I noticed the steering wheel kept turning after I came to the "stop" point. It was then that I noticed the front bolster casting had stress cracked and was blowing hydraulic fluid. Called in the welder and he welded the cast, epoxied and plated it as well, effectively curing the problem with the steering (no leaks). No air in system but still no Aux hyd.

I have aux hyd flow, but it isnt the flow it should be, kind of like a "lazy" water hose flow... it takes about 40 seconds to get a gallon and there is no "significant" pressure behind the flow.

I pulled the spool from the flow divider last night, and noticed a plastic ball floating around in one of the ports. it seemed to be out of round but it is definitely a part of a check valve. I pulled the Control valve from the flow divider and noticed the check valve, seat and spring in the bottom of the pilot are where the ball came from and ordered parts.

Could that little plastic check valve with that tiny spring be the cause behind no aux hyd pressure or did I just find something coincidental? I have a hard time believing that little valve is the cause of it, but I don't know where else to look. All the other spools, springs etc in both the flow divider and pilot seem to be in good condition.

I stopped at the local dealer and talked with a mechanic and they seemed stumped because I have great steering and 3 pt, so that means my new pumps (less than 2 yrs old) are still good.

Any advice is appreciated.

#2 reefever1206

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Posted 16 April 2011 - 09:38 AM

Sounds like relief valve came apart

#3 Owen Aaland

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Posted 16 April 2011 - 02:41 PM

The 656 hydraulics are different from the larger tractors in that the power steering pump also provides oil to the hitch. The auxiliary valves are feed by the other pump. Return flow from the hitch, when it is not being used, is added to the auxiliary valves circuit. It sounds like maybe the only flow you have at the auxiliary valves is the hitch return flow.

#4 k1128

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Posted 17 April 2011 - 07:51 PM

Sounds like relief valve came apart


Which relief valve? I gotta admit, the I&T maunal sucks when covering hydraulics. There is about 1 paragraph that says anything about the auxiliary Hydraulics, and that is a brief snippit about how the main pump supplies majority of the aux with help on the flow fromt he 3 pt pump joing in when 3 pt isn't in use.

The I&T refers to a "joining box" where the two flows meet, yet doesn't say where it is at (Thinking maybe I have a partial blockage) and while the I&T does talk about the relief vavle, I can't find anyplace where it mentions WHERE to find it.

#5 pete 23

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Posted 18 April 2011 - 11:32 AM

The relief valve for the aux valves is in the block that the aux valves are bolted onto. It is a 1 1/8th inch head plug and screws right out from the outside . Has a screen in the end . If you can blow through it at all it is leaking. If you have another IH similar tractor around you can swipe one from that just to try as they cost well over $100. There is anothe relief valve under the plate under seat that is for the hitch only. The fluid joins in that block assembly that aux valves bolt to. You need to take it off completely to get at a check valve inside. Front pump feed power steering and return flow from steering goes to cooling and lube. Balance of oil from front pump goes to aux valves . Hitch pump goes to hitch and if hitch is not being raised, the flow joins front pump flow at aux valves. Some times the flow divider orfice that is only a pressed in disc will disintigrate or turn side ways in it's bore and then all the flow from front pump goes to steering and lube leaveing nothing to aux valves except hitch pump. That orfice is behind the large hose coming from pump to flow divider valve. We sold several 656 with std drawbar so had no hitch pump so hydraulics on aux valves were much slower. Put some larger pumps on some of them.

#6 motiho2

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Posted 18 April 2011 - 06:43 PM

We've got a 656 sucking air as well. Where is the hose you mentioned and how do you acess it to change it? Thanks for the help.

#7 k1128

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Posted 19 April 2011 - 10:06 AM

Pete 23...thanks. I will start digging a litle more!




Motiho2:

Remove the 3 pt top link access cover on the rear diff. Once you can see inside look slightly left of center and you will see a hose coming up out of the oil. Feel it for cracks/splits. Good chance it is shot if you are always sucking air into the system. If it is spilt, you will need to drain rear diff. Once drained you will be able to see the bottom hose connection as well. 12" of 5/8" oil resistant hose and 3 hoses clamps are needed. Put two clamps on top end of hose to ensure tight seal but you only need one on lower end. If you have long skinny arms like me, you can do the whole repair thru the top link access plate. If not, you may have to pull the PTO assembly.

#8 motiho2

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Posted 19 April 2011 - 07:46 PM

Thanks for the reply. We're going to bring the 656 into the shop shortly. I had asked a independent mechanic who trades parts with me and he wasn't familiar with a hose in the rear end. Is the 656 the only one to have this? We both learned something. Great to have a forum like this.

#9 pete 23

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Posted 20 April 2011 - 11:56 AM

That return hose is used only on that style tractor, like 544, 656 etc. The reason they use it is that the reservoir holds about 13 gallons, front pumps moves 12 gal per min, hitch pump moves 7 gal per min so it is difficult to have enough supply for the pumps, there fore, they direct the return flow from aux valves right back into the suction tube to reduce cavitation. It is not a complete answer though, because if you have a source of air entering from say a loader cyl sucking air on the retraction cycle of the cyl it actually keeps putting air into system. Some guys take the hose off completely and have better results. Problem with the hose when it bursts it is normall above fluid level so it really sucks in the air. Other problems with system is if they portion of the manifold the hose connects to under upper draft control housing has a bad o-ring or cracked pipe or manifold it sucks air also. Have seen this happen. Another thing is that when you shut down the tractor, the fluid will drain out of the upper portion of the return hose and there will be air in it and that is why you hear that growling, snarling right after start up of these models with that shot of air going througn pumps.

#10 k1128

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Posted 20 April 2011 - 07:53 PM

Well, the problem was the plastic valve between the flow divider and the Pilot valve. A little tweaking of the centering spool in the flow divider after the new parts were installed and we have aux hydraulics again.

The bad news is the weld on the front bolster didnt hold so I am now faced with the daunting task of stripping the front end down to replace the bolster. One step forward two steps back. Soon I will have a new tractor, but by that time I will either be broke or insane..... either way I won't be able to use it.....LOL.

Anybody have any tips to make my life easier in this newest endeavor?



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