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Front End Loader relief valve squeals when 3 point is used

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jfortune06
Join Date: Feb 2016
Posts: 10 Texas
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2016-02-16          194542


My tractor is a Cub Cadet 7300 but I believe this affects the entire Cub-Mitsubishi line...
I have found some discussion on this issue on various forums including this one...
But no definitive answer. Here is the specific problem which has not yet been fully defined.
When anything in the hydraulic system used, 3-point lift, mid-mount mower lift, ect, pressure is applied to the loader supply line which overloads the loader pressure relief valve causing it to squeal super loud. Using the loader itself does not seem to cause a problem unless you overload it which causes the relief to operate as it should.
The resolution proposed on various sites all point to increasing the pressure relief's activating pressure until the squealing stops. This does, in fact, work. However, I do not believe this is how it is supposed to work. Here's why...
The loader's hydraulic input line is connected to the power beyond port on the hydraulic manifold (below the motor on the right side). I'm no hydraulic expert but I thought the power beyond port does not receive any pressure if any other line in the system (the 3-point cylinder) is receiving pressure. In other words, if you pull the 3-point hitch handle up, you can't use the loader until the 3-point lift is done moving.
This is not how it is working. Every time I move the 3-point lift I can see the hydro lines connected to the loader tighten up. The pressure is enough to cause the relief valve to squeal even with a very light load of 50 lbs or so.
SO...
Do I have a bad hydraulic distribution manifold?
Is something not connected correctly?
Is this just how the system is designed?
Is there something wrong with the 3-point lift causing too much pressure to lift a light load?


Link:   Previous discussion on this topic

 
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Front End Loader relief valve squeals when 3 point is used

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Murf
Join Date: Dec 1999
Posts: 7147 Toronto Area, Ontario, Canada
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2016-02-16          194543


Without knowing a bunch of stuff, including what the various pressure release valve's are set to, and what make the loader is, it's a stab in the dark. Literally.

Beyond that, is this a brand-new tractor with a brand-new loader, or is this a brand-new loader on an older tractor Beyond that, is this a brand-new tractor with a brand-new loader, or is this a brand-new loader on an older tractor?

If you can give us even the basic of details possibly we can help you out.


....

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Front End Loader relief valve squeals when 3 point is used

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Art White
Join Date: Jan 2000
Posts: 6881 Waterville New York
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2016-02-17          194547


Without being able to see it I will tell you that the plumbing work on the tractor is wrong. ....

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Front End Loader relief valve squeals when 3 point is used

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chashm
Join Date: Oct 2013
Posts: 67 United States
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2016-02-17          194549


I have the same squealing "problem" with my 7305 with a 417 loader and a 408 backhoe, so I got out the various manuals.

The standard (as covered in the installation manuals for the attachments) is to feed the powerbeyond hydraulic (P port on hydro block) to the loader, the pressurized return from the loader goes to the backhoe and the backhoe return goes into the tank (T port on the block). The N port on the block has nothing hooked to it when the backhoe is on so the 3-point hitch doesn't go up and down - you have the backhoe on, you can't use the hitch anyway.

If only the loader is on the tractor, the pressurized return from the loader hooks onto the N port which powers the 3-point hitch and presumably the mid-mount mower cylinder. So if you're moving the loader, you can't move the 3-point. In other words, the hydraulic power FIRST goes to the accessories (loader, backhoe, any other aux uses) and then to the built-in stuff. Without replumbing the whole tractor, you're stuck with this.

The 417 loader has a separate relief valve that's between the boom down and up lines. I can't see a setting in the manuals for this valve, but it's not the one that squeals (unless you have a really big load in the bucket or run the boom cylinders to their max). My guess is that it's set for around 2000psi.

The relief valve that's integrated into the loader control is supposed to be set to 1500psi for a 416 loader and 2000 psi for a 417 loader. This is less than the relief valve that's integrated into the hydro block at the tractor which is supposed to be set at 2133 psi. Apparently the design of the loader's control valve has the relief valve 'always' in play so if you're running the 3-point up the loader relief will be the first one to open as it's less than the hydro block's. Ditto for the backhoe, which means your digging isn't as great as you'd like.

The other long discussion on this - "Hydraulic problem on MMM" - suggests that replacing the Cub Cadet loader valve with a genuine Woods valve (the loader is actually made by Woods to Cub Cadet's specifications, including a Danfoss valve which is not what Woods uses on loaders with their name on it) will fix this problem.

....

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Front End Loader relief valve squeals when 3 point is used

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jfortune06
Join Date: Feb 2016
Posts: 10 Texas
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2016-02-17          194551


My loader is the 476 which is a little heftier than the 417. The breakout force is 2530 lbs, where the 417 is 1875 lbs. I don't have the manual for the loader (can't find it online) so I can't get the exact psi spec but I'm guessing it would be a little more than the 417. I wonder if I could set it for 2133 to match the hydro block PSI???
The other issue that I can't figure out is, why does the 3-point lift seem to put so much pressure on the hydro lines when lifting minimal weight? I don't see anything obvious that's binding or causing stress mechanically on the linkage or anything. It just makes me nervous to see the hydro supply lines on the loader jump out EVERY SINGLE TIME I lift on the 3-point and hear the motor lug down a little for the last 1/3 of the lift height.

I linked the tractordata for my loader and the only pic I could find online of a similar tractor to mine. Mine's not quite as rough-looking as this one :) ....


Link:   Tractor Data link for my Loader

 
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Front End Loader relief valve squeals when 3 point is used

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jfortune06
Join Date: Feb 2016
Posts: 10 Texas
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2016-02-17          194552


Also, to answer Art White's questions...
My tractor is a Cub Cadet 7300 which was made somewhere around 2000.
The loader is a Cub Cadet 476 which was the OEM loader for my tractor. It came from the factory this way.
I purchased this tractor used so I have no idea if any modifications to the hydraulic setup were made. Everything appears OEM though as far as parts. ....

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Front End Loader relief valve squeals when 3 point is used

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jfortune06
Join Date: Feb 2016
Posts: 10 Texas
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2016-02-17          194554


My actual tractor. ....

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____________________________________________________________________________________
Front End Loader relief valve squeals when 3 point is used

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jfortune06
Join Date: Feb 2016
Posts: 10 Texas
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2016-02-17          194555


The trailer mover implement that causes the loader valve to squeal. All other implements do the same thing but this shows how light a load I have on it. ....

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____________________________________________________________________________________
Front End Loader relief valve squeals when 3 point is used

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chashm
Join Date: Oct 2013
Posts: 67 United States
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2016-02-17          194558


According to the 476 parts book:
"WM-58625 Valve, 2 Spool Monoblock, 1800psi"

So I would expect it should be set to 1800 psi, eh?

btw, you can get the owner's manual for the 476 online at
http://www.cubcadet.com/equipment/cubcadet/OperatorManualView?langId=-1&storeId=10051&catalogId=14101
then enter the model number 590-476-100. The 476's control valve is rebuildable; the parts page lists a detent kit, a spring center kit, a seal kit and a load check kit. ....

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Front End Loader relief valve squeals when 3 point is used

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jfortune06
Join Date: Feb 2016
Posts: 10 Texas
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2016-02-17          194559


So TractorData is WRONG.
The 476 loader is weaker than the 417, not stronger.
Lift Capacity - 900 lbs
Breakout Capacity - 1675 Lbs
System Pressure - 1800 psi

It says the hose working pressure is 3000 psi. Does this mean I can set the pressure relief for like 2000 psi and be safe? ....

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____________________________________________________________________________________
Front End Loader relief valve squeals when 3 point is used

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jfortune06
Join Date: Feb 2016
Posts: 10 Texas
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2016-02-22          194589


I did some testing on this over the weekend.
I picked up a hydraulic hose, a T connector and gauge from Napa.
I first connected the gauge directly to one of the loader valve output ports to set the pressure relief to 2000 psi. I know this is 200 lbs over the manual spec but this is just a test. Then, I used the T connector with the gauge to connect it in line with the P output from the main Hydraulic block. This way I can monitor the hydro pressure from the pump while in use. When using the loader, the pressure stays around 500 lbs unless I try to lift the tractor with it or something heavy. When I use the 3-point lift, it starts around 1000 psi for a few seconds, then jumps to 2000 psi which causes the loader valve to squeal (since it's in the same loop). This is with absolutely nothing attached to the 3 point. I thought perhaps there is something wrong with the loader valve so I took it out of the loop. I disconnected the loader entirely and connected the P and N ports on the Hydro block as the manual states. I also moved the switch on the side from the "S" to the "O" position. I tested the 3-point again and it acted in the same way, 1000 psi to start, then jumps to over 2000 psi. No loader valve squeal though since it isn't connected but it was using another pressure relief bypass somewhere. It also loaded down the motor.
I thought maybe there is a mechanical bind somewhere in the lift arms but I can lift it myself with no effort.
Do I have a bad 3-point lift control valve?
Bad hydraulic cylinder?
Clogged up line or something? ....

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