Loader valve difficulty

284 International · Dec 24, 2010

I just purchased a Yanmar YM240 with a loader 2 days ago. When I bought it the motor was partly disassembled, supposedly to replace a headgasket. I got it back together and running, though my motor difficulties will probably end up in another thread, but for now, my trouble is with the loader valve. The lift works fine, but seems to lug the engine until everything is warmed up. The bucket curly, however, seems to really load the motor. It curls easily, but when trying to dump the bucket the valve won't move. Applying a LOT of force, or bashing the lever in frustration, sometimes lets the valve move and dump the bucket. The motor lugs when that happens, and feels like it may stall, and no matter what, the bucket is EXTREMELY slow. Letting off the valve brings the motor up to speed again. Where should I start looking? Thanks in advance for your help.

Edited to add: The loader is powered by a separate pump driven off a chain drive from the crankshaft, not by the 3 point hydraulics.

winston1 · Dec 24, 2010

Being in Southern California I don't understand why your loader is slow until warmed up. Proper hydraulic fluid shouldn't require warm up to operate normal. It does sound like your loader valve is not functioning right. Sounds to me like your going to have to take your valve apart, clean it up and install new o-rings or whatever.

284 International · Dec 25, 2010

I'm not sure why it works better once it's warmed up. I didn't do a good job of explaining, I guess: The loader's speed is good all the time, but something simple like lifting the bucket bogs the motor down and it wants to stall. After a few minutes of briefly using the loader in one or two second bursts, it goes up and strongly and lifts several hundred pounds without difficulty. The fluid appears clean and clear, but I don't know if it is the correct fluid. I will replace it after I fix the valve.

I'm very ignorant about hydraulic systems. Is there a how-to on rebuilding the valve? Pitfalls to avoid? I'm fairly mechanically inclined but have no knowledge of these devices. The travel of the little slide connected to the lever on the bucket curl side is much less going in (dump) than it is going out (curl), and that's where the problem appears to be. I'm frustrated by this tractor in a multitude of ways, but have heard and experienced good things about Yanmars, so am not willing to give up quite yet. Thanks again.

mmurphy · Dec 25, 2010

If there is quick disconnects on that bucket valve, unhook and rehook. May possibly not be seating right. Make sure you rest bucket on ground and shut tractor off. With tractor off, work the valves to see if they free up, plus that should help bleed pressure off. Try a couple times if needed.

winston1 · Dec 25, 2010

I am not aware of a "how to rebuild" sight but depending on make and model you might find a parts list out there or drawing to help you. Here is a Prince sheet on valves that would be similar to yours. I have no first hand experience on these valves. http://www.princehyd.com/Portals/0/products/valves/RD5000Manual.pdf

normde2001 · Dec 25, 2010

Swap the lift and curl lines and see if the problem stays with the curl cylinder or moves to the lift cylinder. OOPS! I see in the follow-up post the problem is in lift and curl both. I would replace the fluid.

284 International · Dec 25, 2010

After Christmas festivities are done this morning, I'm going to attempt to disassemble the valve. It seems like the main trouble is with the dump/curl spool. Something is restricting its travel, and keeping the dump cylinder from getting enough flow as a result. Assuming I can discover something and then correct it, I'll flush the system and replace it with fresh fluid once I have access to a store that sells hydraulic fluid.

winston1 · Dec 25, 2010

Keep us informed, I'm interested in just what is wrong. Merry Christmas.

California · Dec 25, 2010

I've read that hydraulic controls are made with clearances so tight that no o-rings are used. You can disassemble and clean but replacement is the only way to remedy excessive wear. Northern Tool sells suitable valves around $200. But if yours isn't dribbling then there's no need to replace it.

My guess is the problem is debris inside the valve. When I replaced a hose I found a big chunk of o-ring that wouldn't pass a tight spot from a return line back into the valve, so that is the first thing I would suspect here.

Was that the Yanmar on Craigslist-Hanford?

That's a great model tractor and you will love it after you get it sorted out. If you would like to see Yanmar-USA's original sales brochure/specifications, click on the link at the bottom of this post.

Welcome aboard, and Merry Christmas!

284 International · Dec 25, 2010

I am preparing to dive into the valve assembly now. Hopefully it will be productive.

California, I was hoping to hear from you. I read about your experiences with your YM240, and it encouraged me to look in that direction. It is the tractor from Hanford. I'm concerned that I bought a lot more of a lemon than I anticipated. The motor is spewing dark gray/black smoke and lacks power, a new and sudden development from when I first assembled the motor and it ran strongly. I'm wishfully thinking and hoping it will somehow clear itself out of this condition, but I'm really doubtful. I'm going to need help getting it running properly here in the near future.