I'm not sure this is the proper forum for this question,but it does concern FEL and hydraulics, so hope someone can help me. I have a Yanmar EX450 compact tractor with a CL400 FEL that I purchased new just under 2 years ago. I've been cleaning out a drainage ditch with the old 580C, and using the 450 to move spoil piles. I can't seem to master digging into the pile w/o either floating or digging a hole. I've discovered that if I dump the bucket and lower it to the ground with the angle down about 20 or 30 degrees, when it meets the ground, it will "float" back, and unless I apply hydro to the tilt down side, it will either float on top or dig. at 1700 rpm, I can count about 5 seconds before down power moves the bucket. Once power is there, it is rock solid. Dealer says this is "sponge effect" and is normal because when I dump the load with rpm @ idle, hydro pump can't keep up, and emptys the cylinder. I've also discovered that if I raise the bucket only a few feet off the ground,dump that 25 or 30 degrees with no load in it, it will do the same thing (float). I've only got 20 days left under warranty, so am going to drive the 60 miles to the dlr tomorrow A.M. and try a different machine to see if this is a fault with mine, or common to all. Dlr says he can install a check valve to slow the bucket tilt down and cure the problem. Sounds like a stop gap measure to me, and I don't need to slow it down. By the way, I had to go to Corporate Yanmar to get any action - have tried to address this with dlr before to no avail. I will say Yanmar got them to call me. Anyone who can give me any advice on this, I would sure appreciate. like to have some ammunition to argue with, or tell me I'm wrong and this is normal.
Most modern hydraulic systems on FEL have an anti-void circuit in the system, usually built into the valve. As soon as you start to draw a vacuum by dropping the bucket at low idle return oil from the cylinder is redirected to the empty side of the cylinder instead of back to tank. Maybe your anti void isn't working or you don't have one. Basically the anti void works like a relief in reverse.
As to the check valve that the dealer reffered to, we use a check valve with an orfice drilled through it on Grapple skidders to slow down the arch dropping, full flow raising the arch and restricted flow when lowering it. This also cushioned the cylinder when it went to full stroke.
Doesn't sound right at all for a machine that is just 2 years old . In my opion the dealer is taking the p**s . You won't empty a cylinder , unless there is a leak or something wrong . "Sponge effect " never heard of that one !
First thing I would get checked would be the control bank , Haddy
TheOldMan, I had a Kubota B17 that did the exact same thing. I went to the Kubota dealer with the machine where they changed the hydraulic filter, replaced the control valve and took the loader cylinders apart looking for the problem. They could not find a thing that helped. They gave me the keys to several same machines on the lot and they all did the same thing. I asked to try a bigger L model and that one worked properly. I asked them to try the L control valve on my machine as the mount was the same. They called Kubota tech support for permission to do so. The L control valve on the B series tractor was both faster and smoother and eliminated that annoying sponge effect caused by the valve not filling the back side of the cylinder. Kubota told the dealer to leave the L series valve on my machine since it worked so well. I was very pleased.
TheOldMan, I have a Yanmar that I built a FEL for it. I ran into the same issue on mine. You are in fact pulling a vacuum on the back side of the cylinder because the pump cannot supply enough oil into the back side as fast as the bucket is pulling the oil out on the other side due to the weight in the bucket. If your loader valve does not have a regen ckt built in then you either have to slow down the drop on the bucket or put a restrictor valve in the line on the drop side. Mine would take a few seconds to recover like yours. I put a pressure gauge on the loader valve and watched it. If I let the bucket drop fast the pressure gauge would go to zero. If I slow the bucket down and keep 100psi or so showing then I would not get the sponge effect. Mine is caused by a 10gpm loader valve (with 1/2" lines), no regen fucntion and a 3.5gpm pump on the tractor. On some valves that have regen, you have to move the valve handle a little farther to get the function to work. Sort of like float but no click feeling.
I agree that it is due to a lack of a regen system built in. These are small economy machines, and lack some features like that that the more expensive tractors will have. The weight of the bucket and load dumping pulls a vacuum like GWS says. When you are ready to dig, you have to let the flow catch up. When you look at how complex the hydraulics are on the larger machines, it is to cure issues such as these. All of that adds cost to it, so your economy machines go without, and the operator has to adjust to accomodate. Restricting the flow will help that problem, at the expense of dumping slowly. It is all a trade off. One other way to do it is when dumping, hold the valve in the dump position a few extra seconds until you hear it come up on relief. Then when you level out, both sides of the cylinder will be pressurised and it will dig normally.
JD - holding the valve in the dump position, at idle, what is a reasonable time for the hydraulics to catch up? How about at 1700rpm?
I don' tknow on your specific machine, but due to the nature of it I would not be alarmed if it took 3 to 5 seconds to let the hydraulic pressure catch up. Maybe a little more if you are idling along, and expect it to be faster at full rpm's. Since you say it does tighten up after it builds pressure, I do not think there is a mechanical problem, just a design that was built to be economical.
I've been interfacing with the dlr and Yanmar, and getting nowhere. I took it upon myself to contact Prince (who built the valve) and had quite a long conversation with thier engr. He insists that it's a cavitation problem, and that installing one way restrictors on the rod end of the bucket cylinders will solve the problem. I don't think that will take care of the whole problem, but I'm willing to try. As soon as I locate and purchase the necessary parts, I'll do that. He said if that didn't fix it, get back with him and he'd work with me. Guess I can't beat that. The lesson I've learned is not to deal with this particular dealer again, and probably not with Yanmar.
I would think that one way restrictors would solve that problem, at the expense of making the dump action slow. It will be a trade off. Also, if they are not properly sized, you may still have the problem, or you may make the functions so slow it is hard to use. I still say it is the way an inexpensive machine will work. The higher dollar machines usually come with better engineered systems, and you pay a large premium for that. Even then, I remember a thread about a customer with a Cat 988H loader that was having the same problem. The machine in question needed an added regen valve that was only an option on that model to correct the problem. I understand there may be more to it, but I would not automatically fault the dealer, as they are working with what they have, and this is normal machine function that most users accept as a price of a cheaper machine. Have you had other problems with your Yanmar?
JD, I started off with a 1982 336D which I loved. I got it hot (plugged rad fins) and after that it smoked and blew some oil out the exhaust. At that time, I had to have a tracrro, and after comparing everything close, chose the Ex450. Sold the 336 to a gent, explaining the smoke thing, and he was onlyh going to mow with it, so wasn't concerned. I had installed a new Yanmar muffler a couple of weeks prior to overheat. He said he was backblading his driveway, it made a big bang and blew a big wad of oily stuff out of the exhaust, and never smoked again. The Ex is a horse. The Cl400 loader it came with is almost a joke. If I could afford it, it would be replaced with the Lx and a CL600.
Thought I should add: Loader valve is Prince Momobloc. It has float on loader spool, and regen on bucket spool. Evidently the regen ckt is not adequate to keep up. How would you size the restrictors? If they're not that expensive, one could always take them off if it was too slow.
Get one that is close to the GPM of your system. There are variable models that will let you adjust the flow rate for the best results.