Air in hydraulics?

[AzChopp3r]

Hi folks,

I have a John Deere 4300 with a 420 loader that I acquired a few months ago. I noticed something goin on with the loader for a few weeks now.

With the loader raised off the ground and bucket level, I can stand in front of the bucket and grab the cutting edge and lift the bucket and it will move about 3 inches. The slop is in the bucket cylinders. No leaks everything looks tight and right with exception to this slop.

So with the tractor running and bucket pointed down slightly, if I lower the loader arms, the bucket will straighten out to the point the slop is gone.

Sorry for not having a better explanation but I probably could post a video if needed.

My thinking is that there is an air bubble in the cylinders or the line and if so how do I go about getting it out?

 

[adirondackmtnman]

It should self-bleed. Do the arms/bucket hold their position if left up for an extended period of time?

Sent from my LGL35G using TractorByNet

 

[adirondackmtnman]

Also...may be a dumb question, but have you checked the hydraulic oil level?

Sent from my LGL35G using TractorByNet

 

[AzChopp3r]

It should self-bleed. Do the arms/bucket hold their position if left up for an extended period of time?

Sent from my LGL35G using TractorByNet

The main loader arms will stay in place but went and looked after an hour the bucket has drooped down.

As for checking hyd fluid, I have not done this and am not sure where to check it. I have an owners manual on order and still have not received. Would appreciate help on this.

 

[Sysop]

The only thing I'm aware you can do without special skills, tools, or taking things apart for further testing; is to cycle the hydraulics through their full range of motion four or five times which should bleed any air out of the cylinders. You may perhaps have a failure of a single piston, or perhaps aren't getting the proper pressures through the system. There are several causes that could create the circumstances you're describing and the only real option is a process of elimination going step by step through the system and test things. Some things would require special tools such as to test pressure on the hydraulic system, some things would just require disconnecting and testing such as unhooking the cylinders from the loader and cycling them. You could also check/change the hydraulic filters.

Let us know what you find!

 

[adirondackmtnman]

The main loader arms will stay in place but went and looked after an hour the bucket has drooped down.

As for checking hyd fluid, I have not done this and am not sure where to check it. I have an owners manual on order and still have not received. Would appreciate help on this.

The hydraulic reservoir on my 5045d has two sight glass windows to check hydraulic levels. The 4300 may be a different animal altogether, especially since it probably has hydostatic transmission. Look around for dipstick/windows around the back of the machine. Sounds to me like the tilt side of the loader valve may be leaking by, or the seal on the inside of the ram in the tilt cylinders may be leaking by if it droops and you're not losing fluid on the ground.

Sent from my LGL35G using TractorByNet

 

[AzChopp3r]

Yes found the sight glass and with loader resting on the ground the glass is full. with loader raised and bucket dropped, the level in the glass drops slightly. No oil slicks on the ground at all. I have even parked the tractor inside the garage for a few days and the floor was clean. This tractor has only 470 hours on it which is low for a 2001.

So If I read correctly, pop the pins from the cylinders at the bucket connection and cycle them fully half a dozen times?

 

[Sysop]

Cycling them on or off the loader should bleed the air (as said by adirondackmtnman they are made to self bleed during operation), having them unhooked from the loader and cycling them would allow you to see any differences in the operation (i.e. one is hanging or not fully cycling causing extra work for the working one). Hopefully a REAL hydraulics guy can chime in and give ya some specific experiences that relate to your issues to give you some sorta direction to look in.

 

[adirondackmtnman]

Hopefully a REAL hydraulics guy can chime in

Agree 100%...we can speculate all day, but someone who deals with it day in and day out would be able to pinpoint a lot better. Is this problem affecting the day to day use of the machine or just something you happened to notice?

Sent from my LGL35G using TractorByNet

 

[J_J]

Install a 3000 psi hyd gage in a tee in the IN port of the first valve and you can see if the correct pressure is being developed.

If the cyl seals are bypassing, you probably can not activate the relief valve. That valve is a good indicator of hyd system health. If it can build up to the set pressure, then the hyd system is good.

If you have a suction leak, you will continue to suck in air and have the same problems.

Several people have already said the hyd system is self bleeding.

You could look in your tank for small bubbles if a sucking leak is happening.

A lot of hyd cavitation will also generate air.