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  1. #1
    Veteran Member
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    Central Ma.
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    7275 Cub Cadet

    Default Loader Woes

    Last week my loader on my 7275 Cub cadet was not operating like it should. You could hear the pump whining sometimes and the loader would operate really slow. Other times it would work just fine. The oil and filter have only about 50 hours on them. I noticed that the lever on the loader valve was hitting on all four sides of the mounting bracket when in use and thought that me be the problem. I thought there was not enough throw for the loader to work right. The lever holes were worn and the retaining pin for the lever was really grooved out. I welded up the pin and re-machined it. The loader lever got welded up and a new cross hole drilled in it. I also took the valve apart to make sure that there was nothing floating around in there. It was clean except for the back end float area which was full of rusty water. I put this back together and it was working fine for two days. Today I was using the tractor and it is acting up again. It appears to have a restriction in the valve or some other part of the system. One of the hoses goes stiff when using the loader lever in any position except the float position. I also noticed that if I very slowly move the lever to lift the loader it will work just fine most of the time. Then all of a sudden it goes into that same slow mode and the pump starts whining like I'm trying to lift 2000 pounds in a 1100 pound rated loader. Any ideas as to what the problem may be. It was doing this prior to my tearing into the loader valve.
    Cub Cadet 7275, FEL, RFD2584 mower, Box Blade, Scaper Blade, York Rake, Snowblower, Rototiller, Stump grinder, Wood Chipper and a Post Hole Digger.

  2. #2
    Super Member 3RRL's Avatar
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    Oct 2005
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    6,812
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    Foothills of the Giant Sequoia's, California
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    55HP 4WD KAMA 554 and 4 x 4 Jinma 284

    Default Re: Loader Woes

    From the intermittent performance, sounds like there is some debris in the line, sometimes clogging, sometimes not. Maybe some of that rust got into the system and is affecting the valve opening/closing? Another thing to look for is maybe your relief valve is sticking or the spring is worn out. That would be like you're trying to lift #2000 all the time and hearing that whine. Fluid might be bypassing via the relief valve instead of being diverted to the work ports.
    Rob-
    ...The Older I get...the Better I Used to be...
    Member of the Month

  3. #3
    Elite Member RonMar's Avatar
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    May 2005
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    2,760
    Location
    Port Angeles WA
    Tractor
    Jinma 284 delivered 06/28/05

    Default Re: Loader Woes

    Couple of questions: Bear in mind I am not specifically familliar with your hydraulic system, only hydraulics in general.

    Have you looked over the suction pipeing between sump and pump inlet?

    When the slow action is encountered, does the engine RPM drop significantly like the hydraulic pump is under heavy load?

    A pump shouldn't make noise, or should I say it shouldn't make unusual noises. The only time a pump should really make noise is when it is cavitating/trying to pump air, or it is under extreme load. The safety reliefs on the system should prevent it from ever reaching a pressure high enough to make excessive noise(with some exceptions I will note below).

    The system is open centered, so the flow is unrestricted and at low pressure/high flow untill you restrict it by sending it to a cylinder(high pressure/low flow performing work). The only thing that should whine is the safety relief valve when it's opening pressure is exceeded by excessive load on the cylinders you sent the fluid to, and it starts flowing fluid to the return port. Most valves supply input flows past the safety which will dump fluid into the return port and back to the resovoir. Typically the main flow goes right thru the valve (power beyond port) to other downstream devices such as a 3PH valve. When a valve is actuated fluid is sent to a cylinder. The fluid comming back on the return working port line from the cylinder also heads to the valve return port and on to the resovoir.

    If the engine is loading down severely when this slow loader operation is happening, check for any restrictions in the return line from valve to resovoir. Work can only be performed when the fluid returning from the cylinder being operated has someplace to go. A restriction on the return line to the resovoir would hydraulically overload the system slowing it's operation. Since the valve safety also dumps to this return line, there is no relief for the pump and it screams(and ultimately dies) and puts a heavy load on the engine. Are there quick connects on the supply and return lines to/from the valve to make removing the loader quicker? Is that line you noted that is going rigid when the problem occurs, the return line back to the sump? If so, check the return line connections and plumbing. Also check any filter canisters or hardlines on the return line. Most filters have a bypass valve that keeps a clogged filter from causing this type problem, or exploding from excessive pressure

    If the engine dosn't load down when this slow operation occurs, the pump may be loosing suction and or sucking in air thru a loose connection, cracked line or bad pump seal/cracked housing. Because of the density difference between air and fluid, it is far easier to draw air in thru a pinhole than to suck fluid along a line. A clogged suction strainer on the suction line would add to this problem.
    Ron

  4. #4
    Veteran Member
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    7275 Cub Cadet

    Default Re: Loader Woes

    Quote Originally Posted by 3RRL
    From the intermittent performance, sounds like there is some debris in the line, sometimes clogging, sometimes not. Maybe some of that rust got into the system and is affecting the valve opening/closing? Another thing to look for is maybe your relief valve is sticking or the spring is worn out. That would be like you're trying to lift #2000 all the time and hearing that whine. Fluid might be bypassing via the relief valve instead of being diverted to the work ports.

    The rust was only in the end cap where the float detent balls are. I blew the valve out completey with air.
    Cub Cadet 7275, FEL, RFD2584 mower, Box Blade, Scaper Blade, York Rake, Snowblower, Rototiller, Stump grinder, Wood Chipper and a Post Hole Digger.

  5. #5
    Veteran Member
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    Mar 2004
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    Central Ma.
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    7275 Cub Cadet

    Default Re: Loader Woes

    Quote Originally Posted by RonMar
    Couple of questions: Bear in mind I am not specifically familliar with your hydraulic system, only hydraulics in general.

    Have you looked over the suction pipeing between sump and pump inlet?

    When the slow action is encountered, does the engine RPM drop significantly like the hydraulic pump is under heavy load?

    A pump shouldn't make noise, or should I say it shouldn't make unusual noises. The only time a pump should really make noise is when it is cavitating/trying to pump air, or it is under extreme load. The safety reliefs on the system should prevent it from ever reaching a pressure high enough to make excessive noise(with some exceptions I will note below).

    The system is open centered, so the flow is unrestricted and at low pressure/high flow untill you restrict it by sending it to a cylinder(high pressure/low flow performing work). The only thing that should whine is the safety relief valve when it's opening pressure is exceeded by excessive load on the cylinders you sent the fluid to, and it starts flowing fluid to the return port. Most valves supply input flows past the safety which will dump fluid into the return port and back to the resovoir. Typically the main flow goes right thru the valve (power beyond port) to other downstream devices such as a 3PH valve. When a valve is actuated fluid is sent to a cylinder. The fluid comming back on the return working port line from the cylinder also heads to the valve return port and on to the resovoir.

    If the engine is loading down severely when this slow loader operation is happening, check for any restrictions in the return line from valve to resovoir. Work can only be performed when the fluid returning from the cylinder being operated has someplace to go. A restriction on the return line to the resovoir would hydraulically overload the system slowing it's operation. Since the valve safety also dumps to this return line, there is no relief for the pump and it screams(and ultimately dies) and puts a heavy load on the engine. Are there quick connects on the supply and return lines to/from the valve to make removing the loader quicker? Is that line you noted that is going rigid when the problem occurs, the return line back to the sump? If so, check the return line connections and plumbing. Also check any filter canisters or hardlines on the return line. Most filters have a bypass valve that keeps a clogged filter from causing this type problem, or exploding from excessive pressure

    If the engine dosn't load down when this slow operation occurs, the pump may be loosing suction and or sucking in air thru a loose connection, cracked line or bad pump seal/cracked housing. Because of the density difference between air and fluid, it is far easier to draw air in thru a pinhole than to suck fluid along a line. A clogged suction strainer on the suction line would add to this problem.

    I do have a power beyond loader control valve. There is quick disconnects on my loader. I found the loader piping guide in my manual last night and will try to see which line is going ridgid when the loader goes into slow mode. It is probably the relief valve that is whining and not the pump. Looking at the stiff line would lead me to believe that it is not a cavitation problem. The motor drops at least a 100 rpm's when the loader goes into this slow mode. When the loader valve is in nuetral there is no whine and the lines are very flexible.
    Cub Cadet 7275, FEL, RFD2584 mower, Box Blade, Scaper Blade, York Rake, Snowblower, Rototiller, Stump grinder, Wood Chipper and a Post Hole Digger.

  6. #6
    Veteran Member MJPetersen's Avatar
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    Warsaw, Poland
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    YM 1510-D

    Default Re: Loader Woes

    I also have a question. What does it take to bring it out of this condition? shutting down, dumping, curling, raising, lowering? Also does it always occur with one particular action but not others or can it occurr with any action?

    Mike in Warsaw
    "In all your ways acknowledge Him and He will direct your paths." Solomon
    YM1510D, YM 1202 tiller, The following home made tools: Quick Hitch, KK copy dirt scoop, imitation Gannon rollover box blade, Forks on 3pt, a Rear Blade with gauge wheels and a 1.5 yd dump trailer.

  7. #7
    Veteran Member
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    7275 Cub Cadet

    Default Re: Loader Woes

    Quote Originally Posted by MJPetersen
    I also have a question. What does it take to bring it out of this condition? shutting down, dumping, curling, raising, lowering? Also does it always occur with one particular action but not others or can it occurr with any action?

    Mike in Warsaw
    Letting go of the loader lever immediately releases the strain on the hydraulics. The operation of the lever in any of the four positions can cause the hydraulics to start to whine. This problem does not occur all the time. Sometimes the loader works just fine. Then out of the blue it will start straining and operating very slowly in all positons. Then it may start working again just fine.
    Cub Cadet 7275, FEL, RFD2584 mower, Box Blade, Scaper Blade, York Rake, Snowblower, Rototiller, Stump grinder, Wood Chipper and a Post Hole Digger.

  8. #8
    Platinum Member
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    Dec 2006
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    700
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    Columbus, Georgia
    Tractor
    Kuborta B2400, L2900, L4330; Caterpillar D3B, John Deere 455D

    Default Re: Loader Woes

    I think Ron is right that the obstruction (if that is what it is) is in the return path from the loader valve to the reservoir. There are only two paths with fluid flowing through them when the loader valve is in each of the four positions: the pressure supply line from the pump to the loader valve and the return line from the loader valve to the reservoir. Of those two, only the pressure line has fluid flow both when the loader valve is in neutral and when the loader valve is activated. Therefore, it must not be the pressure line. But the return line has fluid only when the valve is activated, and that is when the flow slows down. And you said that returning the loader valve to neutral stops the problem, which is when the flow that was going through the return line moves through the power beyond line instead.

    If, as Ron said, there is a filter in the return path (probably between the return line and the reservoir), it could be the source of the restriction as well. Some return circuits have a diffuser (a screen or pipe with holes in it) where the return circuit discharges into the reservoir to break up the return stream so it doesn't roil the fluid in the reservoir so much and stir up sediment or introduce air. The diffuser could be intermittently plugged, but it would take a pretty large something to do that and I can't figure how it would have gotten into the system.

    Finally, the obstruction could in theory be in the return (low pressure) gallery of the loader valve, but it is almost unimaginable that something would be in there after you cleaned the valve.

  9. #9
    Super Member
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    Feb 2006
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    VA
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    JD2010, Kubota3450,2550, Mahindra 7520 w FEL w Skid Steer QC w/Tilt Tatch, & BH, BX1500

    Default Re: Loader Woes

    i think youve got a bad hose. It is closing up internally when you ask for fast flow. A failure of the hose inner liner.
    larry

  10. #10
    Gold Member
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    Jun 2006
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    NW WA State
    Tractor
    1980 AC 5020

    Default Re: Loader Woes

    Quote Originally Posted by JimR
    I do have a power beyond loader control valve. There is quick disconnects on my loader. I found the loader piping guide in my manual last night and will try to see which line is going ridgid when the loader goes into slow mode. It is probably the relief valve that is whining and not the pump. Looking at the stiff line would lead me to believe that it is not a cavitation problem. The motor drops at least a 100 rpm's when the loader goes into this slow mode. When the loader valve is in nuetral there is no whine and the lines are very flexible.
    What's the power beyond hooked up to?

    Assuming it's an open center valve there's always fluid going through the valve to the return line to the sump. Unless the power beyond is plumbed to the 3 pt hitch, or something else, then the fluid only goes through the return line when you use a spool in the valve. If you didn't have the power beyond hooked up and the return line was plugging up it would do it whether you were using the valve or not.

    If the power beyond is plumbed (tee'd) into the return line then the plug (if it's the return line) is between the valve and the power beyond tee connection.

    Monte

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