FSM Sudden Slow Hydraulics

pc96

Member
Thanks to the help of this forum, I've successfully restored my 61 Super Major and I've been using it for work on my wood lot, and lately, for removing snow at my workplace parking lot in Atlantic Canada this winter. Everything is working perfectly with 30 hours on the tach so far.

Last night while using the FEL to plow snow, the hydraulics suddenly came to a hault, well, almost. It was working perfectly for two hours, then everything started moving extremely slowly.

I am running the loader from the tractors stock hydraulic pump via the stock external services valve. Everything is functioning properly, it's just extremely slow all of a sudden. The flow control valve is responding as it should, however on slow they hydraulics move so slow it is almost unnoticeable. On fast, it takes about 45 seconds to lift the loader arms.

The 3pt hitch arms with blower attached are behaving exactly the same. I am not expierencing any issues with the hydraulics bleeding down, they will stay in place for hours with the tractor parked, with zero movement.

The pump is making pressure when measured at the external services port and it sounds normal, however it is down about 500psi to 1800, when I last checked, it made 23-2400psi easily. I drained the oil and inspected the pick up screen. There is a minor amount of debris but it is not even close to clogged.

I am thinking the hydraulic pump got damaged or maybe sheared the woodruff key.
Does anyone have any other suggestions before I remove the top cover to investigate?

For what it's worth, I am runnning universal tractor fluid designed for systems that share hydraulics and final drive lubricant that is an approx 30wt viscosity in the gearbox and final drive. I have seen multiple other recommendations for oils to use in these tractors.

Thanks.

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Take the Auxiliary Service Chest off and see if any O rings are blown before taking the lift off.

Also take it out of Auxiliary Service and lower the lift arms then test pressure/attempt to lift.

If the lift arms creep up to the top of their travel they will cut off the hydraulic flow. They are supposed to do that.

Any possibility of water in the oil? Could that freeze?
 
Thanks for the reply.

I'll start by removing the aux chest.

No traces of water were in the oil.

I did try lowering the 3pt arms and observed no changes but I did not test pressure after the fact. The arms did not creep to the top of their travel at any point.

Now that you mention it, I did see traces of oil around the AS chest where it mates to the lift cover. The o-rings in there are from Agriline. I have heard that aftermarket o-rings are not the greatest. I am heading to the shop again soon... I'll pull it off and report back.
 
I don't see any issues with the o-rings under the aux service assembly.

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It is looking like I'll have to pull the lift cover tomorrow and investigate unless you have any other suggestions.
 
Are the O rings nice and pliable? I have seen them with slightly hardened O rings that cause low operating pressure due to leakage.
 
Thanks skipper. I've put a lot of work into that thing.

The o-rings are not very old. still nice and pliable
 
Have you checked the flow control in the Auxiliary Service Chest? That can stick, I have sorted a couple for friends in the last few months.

Could be an idea to take a hydraulic hose from the port to your loader and run the oil into a bucket of a known size and time how long it takes to fill. Should be about 4 gal per minute, (British Gallons) or around 20 litres per minute.

Trying to check everything before you remove the top cover.

Brian.
 
I found a piece of debris in the flow control valve. it is a piece of orange plastic type material. Is it safe to assume this is what's restricting the flow? is there anything inside the lift cover this could have came from? it strikes me as something foreign.

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I think you have found your problem. Majorman can verify, or disprove this, but I seem to remember that the differential housing and top cover have a coating about this color(I haven't been into one in many moons) I wonder if it could be a piece of that coating that broke lose. Or maybe a piece of foreign material that was in the oil when someone added oil.
 
I got it all back together with new oil and the hydraulics still move ultra slow. Back to the drawing board...
 
Could be the internal paint or could be a piece of red instant gasket from somewhere.
Looks like the top has got to come off anyway. If you have something like that floating around it could be anywhere. A final place to check would be the Pressure Relief Valve. You can take it out, grip the end with holes in and an o ring in a soft jawed vice and unscrew it. Donot loose any of the shims.

Other than that it will be check the o rings on the pressure pipe then take the pump out. We used to do that without draining the oil, working by feel for the bolts then rocking the pump off the dowels.

Check the drive gear key has not sheared then, if you have to split the pump, mark the center housing and the end plates so you know which end goes where. Also make sure you note the way the bearing blocks come out and where the large and small channels go.
 
Thanks. I started by removing the check valve ball and found another piece there. Tried it again with no luck.

Following the circuit, I decided to remove the top cover and check out the unload valve. a few small pieces of debris there as well but everything moved freely and looked very clean.

Lastly, I removed and disassembled the pump and found that both o-rings are completely shot and the shaft oil seal is hardened and cracked. The internals seem fine.

Any idea where I can source parts for this?
 
Your best bet would be a hydraulic component supplier and see if he could match them up. O rings can be made but I do not know how they would work in that situation.

Agriline have rings for the Dexta but do not list anything in their Major parts in the 2021 catalogue.

Sorry cannot be more help.

Definitely check your PRV before reassembly, if bits have got into that, it could be why your pump rings have failed.
 
It's sorted out and working better than ever.

I was able to source the proper size pump o-rings from a local supplier. Since the lift cover was off and I had the parts from a previous order I decided to pull the lift cylinder and replace the U cup seal and the o-rings above the cylinder. I removed the unload valve and control valve to inspect and clean and blew out all the passages. There were traces of whatever the debris was throughout the system in there as well.

Got it all back together and it was operating slightly faster but still very slow.

After stepping away for a few hours, it dawned on me that I never did pull the flow control valve restrictor... sure enough, a huge chunk was caught in there too. An oversight on my part for sure.

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Once that was removed, everything returned to normal and I find the loader runs quicker than it did. The pump is much quieter as well.

Thanks again for all the insight. You guys are a great help.
 
It is medium - hard plastic/vinyl which explains why it did such a good job of restricting the flow. I am 99% sure it is traces of a caplug... however I am still trying to figure out how it ended up there. I used the 3pt hitch for ten or so hours before the loader was installed with no issues. Even if it somehow were inside one of the new loader lift or tilt cylinders upon assembly, it would still be downstream of the pump and would have ended up in the exhaust filter. The pickup screen under the pump is in good condition as well. Either way, I am glad it is together and working again.
 
Not necessarily so, the return oil from the loader does not go through the return filter, it dumps straight to the rear axle from the control valve.

However the oil does pass through the ASC both raising and lowering and if there were any large lumps, they would be in the place where you found them. I would agree that the source of the problem would be the loader, possibly, as you said, a plug crunched up inside one of the rams.
 

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