Auto Parts: Tractor Hydraulic Repairs, hydraulic repairs, o rings

Question
I thought I would ask your help on this.  I have been running a Kubota M108S and the o rings keep blowing.  I was told to turn the pressure release value down.  And that is not working.  Any help is much appreciated.

Answer
I'm not completely sure on how the hydraulic system operates on your tractor, and if I could see it first-hand I feel I could fix the problem as I've worked hydraulic systems on aircraft for 16 years now.

At any rate, here's what I'm wondering, i.e. places to look:

Should there be teflon backups where the o-rings are located?

What pressure should your system be running at?  This will require hooking up a direct-reading gauge to the system.  

Are you using OEM o-rings in the system?

What kind of loads are you putting on the system?  Is it less/more than the system can handle?