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.