Need help with front loader problem

[teamjnz]

Hi Friends..
First I would like to say "Hello" this is my 1st post on this forum.

Now a little backround with my problem. A couple years ago I bought my tractor, used in near new condition, and I have nothing bad to say about this little machine. I should have broke it several time by now with the work I am doing. I have had popped hydraulic lines on the backhoe but nothing major. This tractor is one tuff tractor. My wife and I purchased some acreage around the same time. The property has lots and I mean lots of Eucaliptus trees. I have been removing them to build our home.

Here is my problem. My loader stalls when dumping. If I have something in it and I go to dump it there is no problem since the weight in the bucket it pulls it down to a certain point until the hydraulics kick in, but if it is empty it stalls until the hydraulic pressure builds up to dump it. I have no problems with rolling it back just dumping. There are no visible hydraulic leaks on the tractor or in the system. It can be frustrating while pushing the handle to dump and having to wait 3 to 5 seconds everytime to fully dump my load. The same issue when I use the bucket to smooth or flaten dirt when backing up. I have to wait until pressure is there or the bucket just flops over the pile I am working. Once pressure is there, there is no loss of pressure. So it seems there is no internal leak, just slop in the system. This issue is only with dumping. Not lifting or lowering or rolling back just dumping.

I really don't know much about hydraulic system. So I am wondering if I could have air in the cylinder causing the slop.

Any sugesstions or comments would be great!!
teamjnz

P.S.
I have done all of the scheduled maintainance up to the 100 hour mark. I just passed the 200 hour mark and need to do the next scheduled maintainance.

 

[Theowegian]

Howdy. Welcome to TBN.

Could you tell us all a bit about the tractor make and model along with the front end loader types?

That way, those of us with similar tractor types can perhaps help you.

thanks dwight

 

[JackIL]

teamjnz,

The problem you are experiencing is fairly common especially on smaller tractors due to lower capacity hydraulic systems. It has to do with the hydraulic flow not keeping up. Air gets into the system - cavitation - when the bucket is moved faster by the load causing the return oil out of the cylinders faster than the pressure oil is being supplied. If it happens cycle the bucket from full retract to full tilt several times to purge the air.

To achieve the required flow, operate the engine at higher RPMs. Also avoid "feathering" the control when dumping--dump fast. If your loader valve has a "regenerative" position (usually pushing the joystick to the full right) use that when dumping--it will help prevent cavitation.

Hope this helps.

JackIL

 

[teamjnz]

JackIL -
Thanks for the info. I have cycled the loader buck many time at higher RPMs. It hasn't helped.. /forums/images/graemlins/frown.gif I usually dump with the handle all the way to the right position. Thinking about it I haven't tried full cycling the bucket with the loader all the way lifted up in the air.

Does the oil continually get pumped through the entire system? Or does most of the oil that is in the cylinder stay in the cylinder? Can air get trapped in the cylinder that has to be bled out? That would explain what you have called the cavitation.

Theowegian -
I updated my signature line with tractor model number and attachments.

 

[btolle]

I hate to ask the obvious, but have you checked the level of hydraulic fluid lately?

When you have the bucket up in the air. the hydraulic cylinders are all full meaning the fluisd in the hydraulic reservoir is at it's "lowest" point since the fluid is now in the cylinders.

First thing I would check is to be sure the fluid is full right up to the upper mark on the dipstick and then cycle the bucket with it raised as high as possible, then let the bucket down and check the fluid again once any air is bled out of the system.

While you state that there is no "obvious" leak it is possible that there could be a small leak that is spewing the fluid onto the ground and you are not noticing it.

My old tractor had a small leak and I never noticed it while it was parked in the shed with a dirt floor. When I put it out on the driveway to sell it I noticed a little fluid under it. Turned out to be a leak in the return line which was fixed by tightening a hose clamp.

Bill Tolle

 

[JackIL]

Theowegian -

You say you have cycled the bucket at high RPMs. Do you operate with high RPMs before you start the first dump and when "Back blading?" The pump needs to be up to speed before a demand is placed on it.

Good Luck.

JackIL

 

[teamjnz]

Thanks for the input and suggestions.

Today I talked with a mechanic and he said I will have to bleed the cylinder before doing anything else. He said it sounds like I have air in it, cavitation. He said crack the connection line and push the handle to dump to force out the air then tighten it back up. That should fix it..

Thanks again
teamjnz

 

[JerryG]

Your loader can cavitate every time that you dump a heavy load from it, if the RPM (flow) is to low. It still sounds like what Jack was saying. If the mechanic told you that you needed to loosen the fitting to bleed the cylinder, you need to get a different mechanic. Just cycle the system like Jack said.

 

[DK35vince]

</font><font color="blue" class="small">( Your loader can cavitate every time that you dump a heavy load from it, if the RPM (flow) is to low. It still sounds like what Jack was saying. If the mechanic told you that you needed to loosen the fitting to bleed the cylinder, you need to get a different mechanic. Just cycle the system like Jack said. )</font>

I agree with Jerry.
The cylinders are self bleeding and cracking a line to bleed the cylinder will do nothing more than make a mess.
It will not help the problem !

 

[rbargeron]

I'll get out on a limb here - it sounds to me like the "regen" circuit in the control valve has a leaking internal seal. It is supposed to short-circuit some oil to improve cylinder speed - but if pressure is bleeding into the suction side the weight of the bucket isn't enough to balance it. It's like your system is pressurizing both sides of the piston at the same time. It will dump, but only because the cylinder area is bigger on the push side than the pull side. And it has to work pretty hard to do it.

As always, prompt cheerful refund if info is bogus /forums/images/graemlins/smile.gif Dick B