Slow Dump on LA351 Loader

[Pks]

What would cause a 2 year old LA351 loader to pause during its dump cycle? It tends to do this when the lever is pushed far to the right in the rapid dump position (away from the operator in accordance with the manual & sticker). The hoses have been checked for proper routing-there're OK. The weight of material inside the bucket does not affect the problem. My suspicion is air in the dump circuit. Can anyone provide guidance? Thank you, Peter

 

[PaulB]

My LA301 loader has a slight hesitation - much less than a second - when I go from dump to rapid dump. Always has, I just assumed it was normal. I do know that when you go into rapid dump there is a set of springs and detent balls which engage and hold the spool stem into position (just like when you set the loader to float position), so maybe there is a momentary hesitation to engage a new hydraulic direction of flow??? If this is abnormal, it is the way mine came to me from the factory.

 

[MChalkley]

If air gets in the dump circuit, it won't stay there long. So, I doubt that's in, unless you've got a leak on that spool inside the block. This is unlikely, though. Are you sure nothing has changed?

Mark

 

[Anonymous Poster]

Nothing has changed as far as I know. I do remember removing the quick disconnects at the valve last summer. I had to replace the steel oil line that goes from the block in the front to the block in the rear. But that's it. Why is it that air would not stay in some portion of the lines or the cylinder? Looks to me like it's pretty well trapped.

 

[W5FL]

How long since you changed the hydraulic filter and hndraulic oil (or cleaned the strainer if it has one)?

 

[MChalkley]

All fluid sent into any cylinder, whether to force it to extend or retract, is pulled by suction from the tank (the "transmission case") by the pump and sent to the cylinder under pressure. All fluid leaving a cylinder is dumped to tank. Since air is compressible, it gets compressed on a pressure stroke to infinitesimally small bubbles, which mix with the oil and are carried to tank after a few cycles, at the most, because the air never gets a chance to expand back to any appreciable volume, since the fluid is always under relatively high pressure (from a gas standpoint), even when exiting the cylinder. However, if for some reason enough air is being regularly introduced into the system that you always have air in it, you have a major problem. Likely the fluid level is low, or a suction filter is clogged, either of which can also cause pump cavitation and ruin the pump in short order. Other causes of air introduced into the system are rare. If you think about it, any place air could get in, hydraulic oil would be forced out in great quantity when the circuit was put under pressure.

Mark

 

[Anonymous Poster]

My LA351 also has the slight pause when dumping and has as long as I can remember (3 years old). This does not occur all the time and when it does it only lasts a second or so. I assumed it was occuring when switching from regular dump to fast dump mode. I think this is just the way it works and there is nothing wrong with your machine.

 

[art]

The LA351 loader is advertised as a 2 second dump time and a 2.7 second roll back time. I do believe that that would be at near full throttle.

 

[Cowboy]

Pks
My Case loader has, a dump speed adjustment linkage. On the Case, it is located at the bottom of the dump control lever. Check your manual, or your dealer to see if your's is equipped with an adjustment.

Hope this helps.

Cowboy
BigBoyz Toyz

 

[Pks]

PaulB,

It sounds like mine is just like yours. But there are times when there is a pause, while changing from slow dump to fast. That pause is usually longer than 2 seconds. During the pause, the bucket seems to float. Meaning if the load is just right then the bucket will very slowly tend to dump. But if the load is back slightly, the bucket will slowly move back to the carry position (aka crowd position).

The pause is greatest when I'm lowering the lifting arms and begin to slow-dump. Then as the slow-dump motion begins, while the arms are coming down, I'll change my mind and shift to fast dump. That's when the pause begins. The lift arms continue to come down-no changes there. But the bucket just pauses. My guess is that it's oil starvation within the cylinders. I figure the change in demand, with the arms demanding their own amounts, creates the pause.

BUT... if I start a fast dump while the lifting arms are coming down, there is NO pause.

...goofy huh?