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Larry Cole
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2001-07-04          29808

The loader on my L2550 with a BF400 loader has ceased to function in the bucket curl up mode. It will lower and raise and the bucket will move down but not up, the 3 pt will raise and lower the 400lb bush hog so I assume it's not the pump. From what I can read in the shop manual the left top cylinder controls this function (I could be wrong as usual). Should I be looking at the hydraulic cylinder or the control mechanism,the control has always seeped somewhat but seemed to start dripping when this happened. I took the cylinder loose and purged the oil and reconnected it to no avail, could I take the the cylinder to a hydraulics shop and have it tested if indeed it is the one that controls this function or where would somebody suggest I start.

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-07-04          29812

Sounds more like the SCV assembly than the cylinders. I'd swap the hoses on the bucket and lift circuits. It would be a pretty good indication that the problem is the SCV if the problem moves from the curl to lift function. Swapping is especially easy if the hoses are fitted with quick-connect fittings. Maybe other people know differently, but I think it'd be rare for the piston in a double acting cylinder to be so completely blown that full oil flow could pass by the piston through to the return without developing enough pressure to partially operate the cylinder. There are a couple of other possibilities that seem less likely, given the description. A quick-connect may not be seated or other line obstructions present. The bucket would not move one way and only a bit the other. You'd hear the system relief valve opening in either direction. If an obstruction passed the control valve fittings is present, you could feel the pressure hose stiffen when the valve is operated and also hear the relief valve open. A second unlikely possibility is that a control valve with a float function is connected to the bucket circuit, and operation is putting the circuit into float (the float position usually is a detent at the full-forward position of the valve). If the normal curl and dump functions weren't working, then in float, the bucket would flop down and wouldn't curl. You might note if the dump is powered or simply flops. You also might try curling the bucket with a lever when the tractor is off, with the valve centred and the bucket on the ground. I wouldn't pry, but if the bucket doesn't curl easily then the cylinders and SCV are holding pressure. However, before doing any of this you should be certain that the cylinder that was purged is full of oil. In a normally working circuit, an empty cylinder is charged for the high-pressure line, and air is expelled to the sump through the return. It can take a couple of full 'cyclings' to expel all air. ....

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Roger L.
Join Date: Jun 1999
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2001-07-04          29818

Howdy Larry. We can get you started. First of all, I don't know this loader, but if it is like most of them out there (except recent JD), then what you are describing is in the hydraulic control valve that you work with your right hand. This is called a "dual cylinder hydraulic control valve" or sometimes you hear it as "loader control valve" or even "dual spool valve". It should have 4 hoses coming out the top, and as Tom says you can learn a lot by swapping both right hoses with both left hoses.
Before I go any farther, I can set your mind at ease on your leaky cylinder. That isn't the problem. Neither is it a little bit of air trapped in the lines.
Two questions for you Larry: Is the loader control valve a single stick "joystick" type or does it have two independent control levers? The other and most important question is "does this model loader have the self-leveling bucket? ....

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TomG
Join Date: Feb 2002
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2001-07-05          29824

I am curious about the comment that the manual says '...the upper-left cylinder controls the function.' That seems to suggest the curl cylinders are plumbed in tandem, which I don't think would be usual for loaders. In addition to Roger's question about self-leveling buckets (hydraulic rather than mechanical self-leveling, I imagine), it also would be good to know if the loader uses a regenerative circuit for a fast dump. I know--too many questions and too few answers from me. ....

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Larry Cole
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2001-07-05          29830

Just got back from the barn(spent all day yesterday smoking slabs of ribs and stuffing my face with some friends), after reversing the hoses as Tom suggested I now have a loader that will go up but not down and the bucket curl works fine. So we can assume the problem is in the control, to answer a few questions the bucket is not self leveling and the float hasn't worked on it since I bought it used. I usually to all the work on my tractor but when it comes to hydraulics I'm lost, this should be a simple repair or replace option, the question is has anyone had the experience of having one rebuilt or would I be better off slapping a new one on (I have an email in to the dealer to inquire as to the price of a replacement) There are several hydraulic repair shops here in Asheville, but will the replacement parts be readily available or a Kubota items only.I'll probably wait for a quote from the dealer on a replacement but would appreciate some input on repair also. Thanks Tom for the suggestionof reversing the hoses, at least the problem id diagnosed and I don't have to hunt and peck. ....

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TomG
Join Date: Feb 2002
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2001-07-06          29851

No experience here. Not many repairs needed on my Ford 1710 to date. I'd probably price new, re-built, and repair alternatives to see what can be done and file the experience away for future reference. I do think I'd go for a full re-build job. If the float isn't working, it sounds like a bunch of things are going on with the SCV. Note that some SCV's don't have a control valve with float. A valve with float has a longer barrel out the back than regular valves. It would be real good to get a float that works. I dug a bunch of holes in the wrong places with my loader while trying to get the hang of it. Then, I noticed that somebody had put the float valve on the bucket rather than the lift. I hear that loaders used in haying are sometimes setup like this. Good ribs huh? I suppose I should have kept going with one of my loader holds, and then we could have had a genuine BBQ pit. Fall around here is sort of like August and tomatoes. Everybody is trying to give away moose ribs. Bet they’d BBQ pretty good. ....

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Roger L.
Join Date: Jun 1999
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2001-07-06          29860

Is that L2550 with a BF400 loader a SCV system or is it a typical old style two spool control valve with open center and power beyond? Most SCVs that I have seen are on JDs with closed center systems.
Whichever it is, I'd probably get a price from the Kubota dealer on a rebuild or just bite the bullet for a new valve. I've had mixed luck rebuilding those valves, although some manufacturers offer a rebuild kit for around $100. If you look for an aftermarket replacement, be aware that there are several different thread standards for hydraulics, and if you need thread adapters they add expense. It is also hard to find a medium size loader control valve for a good price. You can find a full size 16-25 gpm loader valve quite easily at a good price, but the smaller sizes are hard to match. ....

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Larry Cole
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2001-07-08          29885

The scv is the one with the elongated portion sticking out back,the price for a new one from Kubota is 918.00 ouch! There is no way to bench test the valve with it off the tractor according to the dealer. I refuse to do business with the local dealer so I have to deal with the one an hour away, It's hard for me to believe a competent hydraulics person could not rebuild this unit even if it is an exclusive unit to Kubota, the kit to rebuild the valve in question is around 100.00 and the seal kit runs 49.95 but I would like to rebuild the whole unit once and get it over with. One does not know if it is in actuality an exclusive unit to Kubota or from a outside manufacturer and hung on the tractor. Anyway I plan to tour the local hydraulic shops on Monday and get an idea if anyone knows if it can be rebuilt. The dealer(an hour away) has bent over backwards giving me advice via email while as usual the local dealer,well.. no use venting here. Thanks guys I appreciate the help.

Larry Cole
....

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Larry Cole
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2001-07-08          29886

Change that 100.00 for the valve rebuilding kit to 303.00, oh me!

Larry ....

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Roger L.
Join Date: Jun 1999
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2001-07-08          29894

Are you sure that is the definition of SCV valve? It sounds to me like some of the terminology is getting messed up here. I thought that you were originally simply speaking of a two spool loader control valve with float? How did we ever get to SCV valves anyway? And would someone please tell me what the heck a SCV valve is and what the initials stand for? :-)
But here is something that I do know. I do know that it is easy to test any hydraulic component off of the tractor. It is simple enough to make up a hydraulic test bench....sometimes it is called a pressure and flow stand. Most every tractor dealer 30 years ago had one, and I don't imagine that much has changed back in the repair bays since them.
If they aren't common tools at dealerships anymore, then here is another chance for someone to go into business for themselves. ....

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Jack in IL
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2001-07-09          29898

Roger....SCV is the acronym for Selective Control Valve. It could be either a basic valve or one with float. The term "SCV" is ofen used by manufacturers of agricultural tractors when referring to the hydraulic controls for implements or attachments. ....

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Roger L.
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2001-07-09          29901

Ok, thanks Jack. From what you are saying I get that "SCV" is a more general term and could apply to any valve. I was confused because I see the term used a lot on the newer JDs which have a closed center configuration. p ....

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TomG
Join Date: Feb 2002
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2001-07-11          29973

I guess the SCV thing is my doing. I grabbed on to the term as I've heard it used to refer to a set of inlet, outlet and control valve sections that make up a control unit and any operating linkage. I suppose it's more clear to say 'SCV assembly,' which is usually how I heard it. It is an awkward thing to name since it is a collection of things rather than a unit. ....

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Larry Cole
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2001-07-18          30225

The end result to this thread is enlightening if to no one else than me, took the control to a local hydraulics shop, after taking it apart and thoroughly examining it the he stated that a check valave and spring were out of place and other than that no damage was apparent. Handed over the 50.00 and took it home and bolted it on, Eureka! the bucket worked, get this the cylinder we were concentrating on was not the problem but a neighboring one (it has three) that housed a relief valve.Apparently the boom would work but not the bucket, so all is well now, the wife is out picking up boulders (groan) and dirt for fill around the new house. Me? working on the the neighbor's hexed riding mower for the upteenth time, oh well it keeps me in tobacco products. Thanks for all the tips guys I appreciate it!!

Larry
....

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