My bucket is floppy.

[Zephrant]

If I set the bucket lightly on the ground, then curl down, it takes 3-4 seconds before enough hydraulic pressure builds for it to lift the front of the tractor. When I'm back-dragging with the bucket, it's tough to get any down pressure as I have to wait those extra seconds after contact.

What makes it so sloppy? If I curl the bucket down to the stops, and hold it until the engine lugs, I can curl/uncurl without the delays, at least until I curl up all the way.

I don't think it used to be that way.

 

[powerstroke444e]

If your running tractor @ full rpm WFO it should help most tractors have this problem @ idle or lower throttle. If I remeber correctly that is why some manufactures use regenitive on dump/curl function.

 

[hanson1999]

your bucket weight is pushing the oil out of the rams faster than it is pumped in. common problem on compact tractors because of low gpm pumps. and the oil being pushed out of the ram is actually less in volume as compared to the side that is being filled by the pump ( the cylinder shaft takes up volume instead of oil).

one way to fix this is put a restrictor in the hose that is returning oil while bucket is dumping. this will slow the oil, causing the hydraulic pump to actually push the bucket down, instead of it dropping on its own faster than the pump can get oil out there!! do not put a restrictor in the line pumping the oil to cylinder on the dump cycle, you want to keep that as fast as possible. overall, your cycle time may slow a little, but you will get rid of at least most of the "flop".

 

[allenr]

Not sure if you are describing the exact thing that I've noticed on my loaders but I've put that sort of lag time (floppyness) down to gravity dropping the loader arms or bucket faster than the hydraulics fill the other end of the cylinder - leaving an air space (or possibly a vacuum).

 

[allenr]

Not sure if you are describing the exact thing that I've noticed on my loaders but I've put that sort of lag time (floppyness) down to gravity dropping the loader arms or bucket faster than the hydraulics fill the other end of the cylinder - leaving an air space (or possibly a vacuum).

Just noticed Hanson beat me with his good answer, however I will add that I've noticed it on all loaders up to and including my Cat 428C backhoe loader.

 

[Zephrant]

Thanks for the answers- good to know that it is not unique, or a known defect.

Shouldn't the cylinders be sealed and air-tight though? How can more oil come out than goes in? I hadn't considered the possibility of a vacuum forming.

I was wondering if there was air bubbles in the oil expanding and causing problems.

 

[allenr]

Thanks for the answers- good to know that it is not unique, or a known defect.

Shouldn't the cylinders be sealed and air-tight though? How can more oil come out than goes in? I hadn't considered the possibility of a vacuum forming.

I was wondering if there was air bubbles in the oil expanding and causing problems.

The oil which comes out returns to the reservoir, the oil going in is limited by the pump - drawing from the reservoir.

I think it safe to assume the "airspace" would actually be a vacuum.

Air bubbles will only occur if the reservoir becomes depleted and the pump draws air.

 

[J_J]

I really don't think you are drawing a vacuum. If that were true, I believe the cylinder would also leak, but maybe not depending on the seals. If there is air in the system, then I believe it is being sucked in at the pump input. Air will come out of suspension at some time, and go to the highest point. If the air did come out of suspension in the cylinder, it would form a bubble, and cause a cushion effect. After the cylinder is cycled a couple of times, the bubble of air should be purged. If the floppy bucket has a mechanical sound, I would throughly check out the cylinder pin and bushings on the bucket for wear.

If there is air in the cylinder, when you activate the valve, the fluid will start to build up, and the bucket may start to move, but will not be at full force. Once the air has been compressed to the fluid pressure, the bucket will appear to work normally. The cushion effect you feel is the fluid , compressing the air. That cushion effect should go away.

After working the bucket for a while, look in the reservoir, using a flash light, and see if the fluid has tiny bubbles in it.

Another thing, If you were sucking in air at the cylinders seals, then you would also be sucking in water, and other contaminants

 

[PANHAPP]

Try raising the loader till the dump cylinders are level,then cycle the bucket to the extents a couple of times to get the air out. It works for me. I think air bubbles in the oil get trapped in the cylinders and does not get pushed back out.

 

[jinman]

If I set the bucket lightly on the ground, then curl down, it takes 3-4 seconds before enough hydraulic pressure builds for it to lift the front of the tractor. When I'm back-dragging with the bucket, it's tough to get any down pressure as I have to wait those extra seconds after contact.

What makes it so sloppy? If I curl the bucket down to the stops, and hold it until the engine lugs, I can curl/uncurl without the delays, at least until I curl up all the way.

I don't think it used to be that way.

I may be really wrong, but since you say that your bucket is sitting on the ground, I think the lag is not caused by gravity or downforce pulling a vacuum. It sounds to me like your cylinder may have leaky seals when it is retracted, possibly due to scoring in the top of the cylinder but not in the bottom. That might account for slower response time when the cylinder is retracted than when it is fully extended. If you had bad seals, the leak would be consistent all the way up and down the length of the hydraulic cylinder, but if the cylinder itself is scored or out of round at the top, you could have the symptoms you describe. If it were a problem with your hydraulic system, it would show up in the 3PH as well, so I think the problem might be internal to the curl cylinders.

You could also swap your joystick functions by swapping your loader quick connects and checking to see if the problem changes. If it does change, that would tell you if it's related to the joystick valves. If there is no change, then it would point toward the loader cylinders.

 

[Zephrant]

One thing more to note- the main rams do it. I can set the bucket down, then push hard down on the bucket, and it takes several seconds before anything happens.

So either it is all the rams or something that is common with them (like air in the linds).
I have 800 hours on the tractor now, 750 with a prior owner that at least did not take care of the paint well.

Would cylinder scoring be obvious or hard to see without taking things apart?

 

[jinman]

One thing more to note- the main rams do it. I can set the bucket down, then push hard down on the bucket, and it takes several seconds before anything happens.

So either it is all the rams or something that is common with them (like air in the linds).
I have 800 hours on the tractor now, 750 with a prior owner that at least did not take care of the paint well.

Would cylinder scoring be obvious or hard to see without taking things apart?

Cylinder scoring is impossible to see without complete disassembly and inspection.

I'm really astounded that you say it takes several seconds to respond. If you said a moment, half a second, or even a second, I could understand that, but you say "several seconds," and that seems an eternity to me for hydraulic response.

If you system only pumps 5 gallons per minute, in one second, it should pump 1/3 of a quart of fluid into the cylinders. In three seconds, thats a full quart of fluid and probably is all the fluid it takes to extend both cylinders at least 5 or 6 inches. It just doesn't make sense to me that you could have anything causing such a delay without a huge leak somewhere.

EDIT: Since you say both lift and curl do this with the bucket sitting on the ground, I don't think cylinder scoring is your problem. It almost sounds to me like you have a delay in the open center system closing to apply pressure through the joystick. If you have something sitting on the ground on the 3PH and raise the lift lever, does it also have a delay of several seconds before the lift starts up? If it does, the whole hydraulic system is responding slowly.

 

[J_J]

Zephrant has not connected a gage to the pump, and therefore has no idea of the original pump pressure. If the pump is pumping at the rated pressure, and the lines and cylinder is full of fluid, then as soon as the valve is activated, something should start to move. I don't believe he said he had made the valve go into relief yet either. With all power off, can you shake the bucket by hand? Is it loose in any way. If you say it flops back and forth about 5 in, then something else is wrong. Pins, bushings, etc.

 

[Zephrant]

The 3PH raises instantly- in fact it comes up so quickly it is hard for me to raise it just a 1/2" when I'm trying to grade with the blade. Down is gravity controlled on this unit, so also has no delay.

When I say "several seconds" I mean that it is 4-6 seconds when the tractor is at idle, and 2+ when at full throttle. I normally work around 2000 rpm, not at full throttle.

I did gauge the pressure last spring- it was within range then, but I'll do it again and see what it says.

So I just went outside in the cold (32 degrees) and dark to time the delay exactly. I warmed up the engine for about 1 minute, then went full throttle. The system was flawless- no delays, moved fast, no issues at all.

So either being cold or sitting for 24hrs makes the problem go away.

How would I tell if I was getting air bubbles in the fluid? It's pretty tough to say just from the little sight glass.

Next time I can run the tractor for a while I'll test it when I first start out, and again when I'm done for the day and it is all warmed up.

Thanks a lot for the help all- I appreciate it-

Zeph

 

[DEON]

Zephrant, I previously owned a Kubota B1700. The loader did just what you are explaining. If I pushed down to back drag, then lift the loader arms, the bucket would flop down. I could get off the tractor and rotate the bucket about 1/3 of it's rotation by hand with absolutely no resistance. I brought it to the dealer, under warranty. They tried everything with no results. I finally asked to try out a same tractor on the lot and that one did the same thing. I test drove a L3010 and that one worked well. We removed the loader control from the L3010 and mounted it to the B1700. It fit perfectly but had a longer lever. The problem all but disappeared. Only occasionally noticed it a very slight bit from then on. Kubota tech support gave them permission to leave the control valve on my machine so it is still on it today. The valve worked faster and probably allowed oil to fill the back side of the cylinder in due time to solve the floppy cylinder syndrome. I now own a Kioti CK25. I have noticed this on the CK but only very slight and very occasionally, probably when running at to low rpm.

 

[Zephrant]

DEON- That is exactly what I see too.

I guess I'm becoming convinced that it is inherent in my system, and that there is no easy fix. I've considered replacing the loader control before because the linkage are worn out and it makes the lever sloppy.

Thanks for your post!

 

[J_J]

There is something that isn't making sense here. If you raise the bucket up and down about four times, and leave it at about 4 ft off the ground, then go to the bucket and try and shake it while observing the cylinders. Is the bucket only moving, or is the bucket and cylinders moving?

 

[J_J]

On your valve, can you observe if the spool is moving when you are moving the levers. Just how loose are the levers?

 

[Zephrant]

JJ- The bucket is solid if I do that test at full throttle. Just a little rattle/slop from the pins. I'll test again this weekend though, also at idle.

The levers are pretty sloppy- I'll measure a little and post tomorrow.

 

[Zephrant]

Well I finally made a connection- when I load the bucket with gravel then dump it, the bucket is very floppy - I can move it by hand and see the cylinders move in/out several inches. When I go full dump and hold it for 3+ seconds (until the engine lugs) it is fine again.

Without a load in the bucket, it is pretty clean- no issues.

So as mentioned above, either air or vacuum is behind the cylinders, making it mushy.