Hydraulic sag/drift

[fireman275]

Greetings. I'm brand new to this site AND so tired I can barely keep my eyes open. I've been working on reroofing my house on my days off. Because of my newness and sheer exhaustion, I apologize for my stupidity in asking a likely common question.

I bought a 2006 Kubota L39 TLB with 136 hours on it. It looks pretty much brand new (but I do know that bad stuff can happen even if it looks new). I've used a B21 for a long time and it seems that the hydraulics on my L39 aren't very strong. There is also a significant drift in the tilt of the bucket. I've been using the pallet forks for an elevated platform while I work in the roof. Within minutes, my forks have a 10 degree drop (I'm guessing). I haven't seen any leaking in any of the cylinders or lines.

I just don't get the limited capability of the bucket and the sag. Can you give me some advice on where to start? How do I test the strength of the loader compared to the factory settings, can the strength be increased? How do I fix the sag...

Thanks for your input and again, I'm sorry for the newbie content. I'll do better when I get some stuff done and some good sleep.

 

[J_J]

Put a gage in the system and take some readings. Cyl could be leaking, Valves could be worn. Find out what the pump psi should be. Activate different spools and 3ph and note the pressure. With internal leaks, you will not see any fluid.

 

[mmurphy]

Take a look at AKKAMAAN's thread "Cylinder drift".
There is no stupid questions ever posted here, just sometimes stupid answers!

TractorData.com Kubota L39 tractor information I guess tractor data does not have info on the hydraulics you have. Curious to know if the tractor is shut off, operating valve when this is happening?

And also as JJ suggested.

 

[fireman275]

JJ and mmurphy, thanks for your replies. I'm awake and getting ready to go home for the day and back on the roof. I knew I would forget something! Yes, the tractor is shut off when the obvious sag occurs. And I should say that I understand that some sag is normal but this is very quick and it happens when the front bucket is on and empty as well so it's not just because there is some weight on it.

JJ, what kind of guage would I use and where would it go?

 

[mmurphy]

AKKAMAAN's second example gives a pretty good description of what you have going on.

 

[J_J]

If your pump is below 3000 psi, use a 3000 psi hyd gage . If above, use a 5000 psi gage. Can be found at Hyd shop,. TSC, Northern Tools, Surplus Hydraulics.

Tee it into the input to the FEL valve, or make it so it could be plugged in at different points on the tractor, using QS's.

Something like this.

https://www.surpluscenter.com/item.asp?item=21-1044&catname=hydraulic

 

[Stonehaller]

For checking the system pressure, you can equip a gage with male quick disconnect and plug it in the coupler for the backhoe hydraulics. It should be about 2750 psi. There are three lines from the tractor to the backhoe. The smallest is the swing pressure. The tank line has a male quick disconnect on the tractor side and the main pressure (from PB port on loader) has female quick disconnect on the tractor side. Rest the hoe on the ground, then with the tractor off, move of the levers to relieve any trapped pressure. Unplug the pressure line and install the gage. There are two levers on the back of the tractor for routing the swing pump to tank and the main hydraulics to the three point when the hoe is removed. Move the two valve levers to the backhoe removed position (should be instructions printed on the tractor). Start the tractor and set throttle to about 2500 RPM. Briefly move the valve levers back to the backhoe installed position to take a reading on the gage. Once you get a reading move the levers back as you are deadheading the pump.

As stated by mmurphy, check out AKKAMAAN's thread Cylinder drift...... - TractorByNet.com and check your curl cylinders to see if the piston seals are leaking.

The L39 has a pretty complicated loader control valve that includes PO checks and a self leveling function. With so few hours on a four or five year old tractor, it is possible there is some corrosion in the valve causing problems. Have you tried with the self leveling both on and off?

 

[AKKAMAAN]

There is no stupid questions ever posted here, just sometimes stupid answers!

Thats the best reply on a post in a long time....I just love that one:thumbsup:


The way the bucket tilt works on this Kubota....(most likely on all Kubota FEL's)...the bucket is held UP by pressure on the rod side of the cylinder.....a few different leaks is possible as a fault....If the only fault is the piston seal, that can be check this way....
>lower the FEL to the ground.....
>disconnect the rod side hose from the control valve, QD would be great, >otherwise plug the hose and plug the port on the control valve.....(you can do this disconnection/plugging where ever the two tilt cylinder have one common line)
>Lift the FEL off the ground and check if you have the same drift or not. If you have the same drift the cylinder piston seal is leaking, if no drift at this test, the control valve is leaking, probably through a work port relief valve, the same port as the disconnected one, the rod side port....