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Hydrolic Information for my T290

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Lou Farraher
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2001-11-07          33021


I have a Millenium T290 with about 40 hrs on it..I don't know if this is normal..but when I have the loader in floater position...Giving it gas will raise the loader..Is this normal or do I have a hydrolic pump problem?Thanks for any help!!Lou



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Hydrolic Information for my T290

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Art White
Join Date: Jan 2000
Posts: 6898 Waterville New York
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2001-11-08          33025


Yes you do have a hydraulic problem. In float the loader should not be raising, if anything it should be falling to the deepest position it can get to unless when driving ahead the bucket is rolled back so it is just riding up on the ground instead of digging in. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-11-08          33026


That doesn't sound normal to me. However, the good news is that the pump isn't likely to be the problem. A float circuit essentially disconnects a cylinder from the pump and connects its two hoses together. In float position, oil can flow freely from on side of the cylinder to the other so the bucket is able to follow the contour of the ground. However, I believe a regenerative circuit can be thought of as a float circuit that gets pressure. A regenerative circuit will move a cylinder from the piston, rather than shaft, end. It sort of sounds like what you may have., and your float circuit may not be fully isolated from the pump. If I had to guess, I'd bet on the loader SCV, and probably something about the joystick linkage. I have a set of in-line control valves for my SCV rather than a joystick so I can't say much about them. I do know that there is a definite detent position on my lift valve that places it into float. You know when it goes into float. The bucket flops down to the ground and stays there irrespective of engine rpm. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-11-08          33032


Here I am back for a second go this morning. I installed a new cordless optical mouse, and I can't think of a better place to test it I guess. Art must have made his comment when I was still writing mine because I didn't see it until now. Art's comment about the bucket digging in did trigger a thought. If the blade digs in while the loader is in float, forward motion of the tractor will raise the bucket. Upward force is applied to the bucket and it floats upward. In this case, the float is working normally. Adding throttle increases the chances that the bucket will dig in, and it might seem like the higher rpm's are lifting the blade. It happens to me frequently, and it also happens if the bucket is curled back too far when I trying to scoop up the last of a pile. In that case, the blade doesn't dig in, and it just rides up over the pile. If I don't notice, I just hope nobody is looking when I go and dump about two dirt clods out of the bucket. Anyway, it's always good when a possible explanation is that nothing is actually wrong. In the context of digging in the blade I’ll note that it's poor practice to use the blade in an extreme as a substitute for a dozer blade. It's pretty to break things that way. ....


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Hydrolic Information for my T290

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Lou Farraher
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2001-11-08          33038


No digging or forward movement..Just in nuetral..Lay the bucket down then rev it..and it raises..
Someone at work mentioned some adjustment to some valve..Sounds right maybe??
I can rebuild cars or trucks from the ground up..trannies and all..but tractor or hydrolics of them is somewhat new at this point..
But being new..I believe warranty still covers it.
At least I hope so..

Lou ....


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Hydrolic Information for my T290

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-11-09          33046


The bucket raising in float while the tractor is stationary sounds definitely hydraulic. Warranty coverage is good to have. After my second comment I realized I said something not quite right. When trying to scoop up material with the loader in float, the blade may dig in if the angle is too sharp. I said the bucket lifts. I meant to say the tractor lifts--the loader and tractor sort of jack-knife, and that's something to avoid. There are quite a few threads in the archives that describe tractor hydraulics. I'll try my hand at a bit of explanation and try not to ramble for too long. Most compacts have open-centre hydraulic systems--so called because the pump continuously pumps oil from the sump through the high-pressure and return lines back to the sump. The lines are relatively large and only about 100-lbs. pressure is produced. When a control valve for a double-acting cylinder (like loaders have) is operated, the high-pressure line is blocked (at the centre of the valve). Pressure is developed ahead of the blockage and a low pressure return line to the sump remains behind the blockage. At the same time as closing the center, the valve opens one line to the cylinder to the high-pressure side of the valve and the other cylinder line to the low-pressure side. Pressure moves the cylinder in one direction and more oil is pumped in. Oil on the other side of the cylinder piston is expelled through the low-pressure side and return line. When the control valve is operated in the other direction, the high and low pressure lines to the cylinder are reversed and the cylinder moves in the other direction. That's the basic description. A power-beyond valve is a variation on the basic idea that has two return lines form the control valve assembly rather than one return. 3ph hydraulics also work differently. Many farm tractors have closed centre hydraulic systems. If I had to guess about your loader right now, I guess either the valve is defective or the linkage isn't putting the valve fully into float. I think I mentioned that if both sides of a cylinder get pressure, the cylinder would move toward the shaft side. The reason is that the piston side of the cylinder has more area for the pressure to work on because the other side connects to the shaft. I think that it's at least theoretically possible for a control valve to deliver pressure to both cylinder lines if the valve wasn't fully into the float position. ....


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Art White
Join Date: Jan 2000
Posts: 6898 Waterville New York
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2001-11-09          33053


For the information you have given us, it is in the valve. To replace it will end your problems. Call your local dealer. ....


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Hydrolic Information for my T290

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Lou Farraher
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2001-11-09          33066


Thanks to Tom and Art..
I looked into the spool valve..and didn't really see any adjustments..
It is a star loader they use on the T290 machines,...
Anyway..I did get in touch with the dealer and looks as if they agreed..it was the valve..since the rest of the hydrolics are working fine..
And since only 36 hours and new..warranty..
Thanks again you two..

Lou ....


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