Backhoe Backhoe spool valve seals leaking, anyone else?

[onelup]

Hey guys, just checking to see if anyone else is experiencing this problem. We'll start by saying that I have replaced the control stick seals at least 4 times over the last seven years (twice under warranty). I bought the machine new in 2005 (DK 35 w/loader and backhoe) and have about 2000 hours on it. I work the machine and may push it's capabilities from time to time but I just don't get it. I have had some other problems (particularly with the backhoe) but this is over and over again. Now the bottom covers on the valves are leaking all over so I removed them and found that virtually every seal in all of the valves are shot. The seals seem to have been made out of a material that does not mix with the oil. The seals turn to a bubble gum like substance and mush up and start leaking. You can mash the together and it looks like a piece of gum, they turn into one piece!

The oil, filters and everything has been maintained to spec. I am using the correct hydro/trans oil. My dealer shrugs his shoulders and says that me and four other customers have had a similar experience and he doesn't get it either. After the second set (on the control sticks) I noted that the seals he gave me were different than the previous ones and held up better but still began leaking after only two years.

I'm going to contact the valve manufacturer (Nimco) and see if the have any updated seal or reasons for this happening.

If any of you have experienced:confused3: this or have any possible solutions I am all ears. Thanks ahead of time.

 

[Harry in Ky]

My first thought would be the plumbing of the valve stack. I've seen any number of valves(loader and otherwise) plumbed in series without a sump return(third hose leading back to reservoir, typical power beyond configuration). The spool seals on many valves are not designed to withstand full system pressure and need the low pressure return to sump access. Does your backhoe valve inlet section have the third hose? Next thought is that if the original seals or Orings failed as you described, it's possible the manufacturer's machining tolerances may not be much better than their choice of Oring material. I've seen a number of Nimco valves, and they seem to be a good product, but brand names don't always indicate quality any more.

 

[wdchyd]

My first tought would be either the hyd oil is wreaking havok with the seals (not compatible) or the seals are not the right material (they should be buna N-70 durometer...not viton)

my second thought would be that there is excessive back-pressure on that control valve, but that doesn't explain orings turning to mush

 

[onelup]

My first tought would be either the hyd oil is wreaking havok with the seals (not compatible) or the seals are not the right material (they should be buna N-70 durometer...not viton)

my second thought would be that there is excessive back-pressure on that control valve, but that doesn't explain orings turning to mush

Thanks for the advice. I'll post some pics of the of the bubble gum orings later on this eve. I think the new ones are made of polyurethane, they are translucent yellow/white color. the originals were white.