Front End Loader Pressure check

dex3361 · Sep 18, 2009

My friend has a L4400HST and was questioning the FEL lift ability. The first pic the location of pressure relief block. The second pic is the hex head that holds the pressure relief spring and adjustment shims.

J_J · Sep 18, 2009

dex3361 said:
My friend has a L4400HST and was questioning the FEL lift ability. The first pic the location of pressure relief block. The second pic is the hex head that holds the pressure relief spring and adjustment shims.

What is the question?

You should check to see what the relief pressure is, and check the pump pressure. Relief pressure should be 50 to 100 psi below pump pressure. If the machine can not lift the advertised load, there are problems somewhere.

dex3361 · Sep 18, 2009

Before we did any adjusting of course we checked the pressure at the FEL quick connect. We held the control valve open till the guage topped out at 2540PSI with the engine turning about 2000 RPM.The Specs call for a max of 2631PSI. We used a wet dry vac attached to the hydraulic fill opening and on to keep from loosing any hydraulic fluid. The pick of the valve with the releif valve spring removed is with the resevior full and the vac on.

dex3361 · Sep 18, 2009

Not really a question just a post on the process and of course running it by the knowledge board for technical accuracy. I have read a lot of your posts JJ and I always am amazed at the vast knowledge and skill that shows in the gadgets that you make and the reliable advice given.

dex3361 · Sep 18, 2009

We removed the spring/shim holder of the relief valve and I included a pic for clarity also another pic of the valve body that is a little clearer. the original pressure of 2520PSI is about 110PSI low and he wanted to put it at the top of the acceptable range. The shims add aprox. 38.4PSI for each 0.1mm added. so we added 0.3mm shims the existing shims and reassembled the spring assembly.Threw a shim still in the package for reference in the last pic.

dex3361 · Sep 18, 2009

The results are in the first pic with the pressure pretty muckh on spec at 2630PSI. My friend tested the loader and says he can tell a difference in the added 110PSI. I had adjusted the relief on my tractor a few months ago and I wanted to document the process for the next person who might want to check or adjust the pressure relief on their tractor (mine is a Kubota L4400 as well).

J_J · Sep 18, 2009

You have to be careful here. If the pump gets a little weak and loses some psi, then by you raising the relief valve settings, you just might set the relief valve at a higher psi than the pump, and the relief will never come on.

J_J · Sep 18, 2009

dex3361

I would write down the pressure, while the tractor is new, to use as a reference for later truble shooting.

dex3361 · Sep 18, 2009

Good Idea JJ I have mine noted in my tractor log book(original PSI and shims added) and I will make a not of the one we did today. I made sure we did not exceed the factory spec and the pressure that we set the unit at today is in the acceptable range. The acceptable range is 2489PSI to 2631PSI out of a Kubota shop manual. By the way when I did mine it was 280PSI low and was actually below spec. It made a very noticable difference.