Go BottomHydrailic surge on TC 35
 | loganWildman
Join Date: Jan 2004 Posts: 27 Hoosier State 
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2004-04-05 82268
My TC 35 hydraulics has just started surging when the tractor is idling. Tonight, the bucket was rising and dropping a 1/2 inch or so with this surge. And the attachment was doing the same.
Yesterday I hooked onto my finish mower and left it raised and shut the tractor off, and within 5 minutes it had dropped to the ground.
What is going on with my tractor?
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2004-04-06 82286
It'd be good to have more information here. I wonder what the idle rpm is and the problem has been noticed at the rpm before? I also wonder if the bucket cycling was when a valve was operated or when all were in neutral? Was the 3ph in neutral when the tractor was off? Does the 25 have power steering and if so does it have it's own pump or use a priority valve?
If the oil and filter has been there for awhile or you aren't sure of their condition I'd change them on principle. I'd also check any clamps on the suction hose for tightness and inspect for breaks and look for froth on the dip stick after the tractor has run for awhile.
The bucket cycling is a bit mysterious unless the explanation is that it's normal at very low rpm's. There are some possible explanations but maybe the basics and more info should be worked through first. The 3ph leak down may be a separate issue. ....
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 | beagle
Join Date: Jan 2004 Posts: 1333 Michigan 
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2004-04-06 82315
Could be air being drawn in on the suction side of your system. Don't know if your tractor has HST, but you may have a leak on the suction side that is causing air pockets. Check all fittings on the suction side. You didn't mention any oil noticed anywhere, so it seams to be on the suction side of the system. Air pockets can cause the mysterious actions you are describing. After checking all connections, cycle the power stering and the loader to remove any trapped air.
Start with the simple fixes, work from there. ....
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| Abbeywoods
Join Date: Jan 2004 Posts: 110 New England
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2004-04-06 82321
It certainly sounds like Beagle is on the right track, air in the system would cause such behavior. Air normally enters any hydraulic system after it has been unused for even a short while, like overnight, but nearly all modern cut systems bleed the air after a few cycles of the control valve. If the implement(s) is/are doing what you describe without you touching the control valve, then you have something going on beyond normal.
It is possible that your pressure relief valve(s) is/are not operating properly, or you may have pump cavitation (where your hydraulic pump is actually pumping air into the system). In any event, as Beagle suggests, eliminate the simple things first. The NH TC35 has dual pumps, so rule out the power steering pump. Now if the problem doesn't remedy itself after cycling the control valve, run a system pressure test and also test your hydraulic fluid for water. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-04-07 82367
A sizable suction line or filter problem likely would cause the hydraulics to become increasingly spongy with loss of power and then stop working after around a half hour of work. The oil would be hot and frothy. If that's happening it would almost certainly be a suction side problem.
It might be good to say how the cycling was observed. Was it during a lift at low rpm (under 1000)? If it happens when no loader valve is active, the cylinders should be isolated from the pump and high-pressure line. General laziness of components at very low rpm seems like a possibility.
A five-minute leak-down for the 3ph seems excessive unless the mower is too heavy for the hitch. I wonder if it cycles up and down when the hitch is in neutral and the tractor is running? ....
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| loganWildman
Join Date: Jan 2004 Posts: 27 Hoosier State
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2004-04-07 82396
The mower was a 6 ft King Kutter finish mower, weighing maybe 500lbs tops. So I don't think it was too heavy. I changed the hydraulic oil last night and there wasn't any froth in it. Yesterday, I stopped by my dealer and discussed it with them. The service manager thought it was the seal on the ram of the internal lift cylinder for the 3ph. It still has warrenty left on it, so I am going to let them fix it! ....
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 | Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada
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2004-04-07 82399
I'm jumping into this thread a little late here, but I think something doesn't make sense here.
In the original post it says the bucket was rising and falling, and the mower on the 3pth was also.
Presuming there was no movement of the controls to cause this motion, how could pressure be rising and falling in a closed circuit?
If a seal is leaking it would cause the subject componenets to either lower or rise to the limit of the possible travel. It could not, that I can imagine, cause a cycling action.
I agree with the suggestion that cavitation induced air pockets would, and do, cause 'sponginess' in circuits, but it cannot cause cyclical motion that I could see.
It sounds more like there is some sort of intermittant pressure getting past the controls, this can happen from inproperly routed PB's and such, where the PB is in the return side and is causing compression against the air on the other side, then the relief valve opens and the air moves the cylinder back, then the relief valve closes and it goes around again.
Best of luck. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-04-07 82420
Me too Murf! The description remains something of a mystery. It sounds like the dealer is going to attend to the 3ph. A leaking cylinder or any of a few valves in the hitch could cause leak down and then the position control linkage would kick in to raise it back up.
I can see cycling in the 3ph but I sure have trouble seeing it in the loader and even more trouble if I try to connect both the loader and 3ph description to one problem. There are various ways to get pressure drops in most parts of a system but not many ways to get surges. Maybe a description different than 'cycling' would be more appropriate or maybe it's just normal operation for the loader. ....
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| loganWildman
Join Date: Jan 2004 Posts: 27 Hoosier State
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2004-04-07 82442
Weeeelll, here's what I think was going on. The day I noticed the bucket rising and falling, I had my pulverizer on which weighs around 1100 lbs. I think the hitch would start to drop, and the hydraulics would pick it up. This cycle was going on constantly, causing the front end to shake. I am taking it to the dealer the 19th. I'll let you know what they come up with. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-04-08 82459
Yes, sort of sounds like mystery solved. My fault in part since I went for the loader problem to start with. It was the more interesting of the two descriptions and I always like a mystery.
Good it's getting fixed under warranty. Outside of warranty, if big weight is left up for long periods it likely takes some life out of the system--not saying that's the practice though. Hope it was getting close to oil change time anyway or it had been a few years. Changing oil usually is a good idea every few years especially in cold climates even if it's only been used for few hours. I think owner's manuals specify oil changes only in terms of operating hours. For that matter I don't think manuals say that it's good to change coolant every two years in diesels.
....
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| loganWildman
Join Date: Jan 2004 Posts: 27 Hoosier State
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2004-04-08 82514
I hadn't changed the hydraulic oil since the first 50 hour service, so it was time. It has always been a rule to drop the hitch before turning the hitch off, however not too long ago, I forgot while trailering to a jobsite and had the weight box on. Hopefully that wouldn't have caused it though. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-04-09 82555
Far as I know sitting everything down on the deck is far better practice although I'm not sure owner's manuals contain warnings. Trailoring can produce very high load shocks at highway speed and I have heard of hoes and maybe loaders breaking things. However, I don't recall anything about damage to the hydraulics.
Virtually all 3ph's and many loader valves etc. have their own circuit reliefs that guard against high load shocks when control valves are in neutral. These reliefs usually are set around 1,500 lbs. above system relief pressures but their presence in a system would limit the severity of very high load shocks. Depending on circuit reliefs wouldn't do the hydraulics any favours though. ....
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