New Holland LB75B Nuisance Hydraulic Leak

[wsand90]

I have a 2005 New Holland LB75B backhoe. I have a continuing hydraulic leak from the hose that attaches to the output of the hydraulic pump. It utilizes an o-ring to seal pressure. I have replaced the o-ring and there is no leakage. However after about 4 hours of operation, the hose at the fitting will leak profusely. When I remove the fitting, the o-ring is distorted, cut and sometimes split through the horizontal plane. One time the o-ring must have extruded from the recess area because the o-ring had a small "pinched" surface on the outer diameter. I have purchased a new hose and have ensured all sealing surfaces are clean and smooth. The o-ring per the parts manual is 0.625" x 0.070", nitrile with a Duro value of 90. When you order the o-ring from New Holland it is specified as 0.614" x 0.070", nitrile and Duro value of 90. The replacement o-ring fits securely in the recess area of the fitting. I try to not turn the hose when tightening the hose coupling nut. I thought possibly the hose was moving after contacting the o-ring during tightening the coupling nut and the movement was destructive to the o-ring. Last replacement I greatly tightened the coupling nut and made note of the hose position. Same result and the hose did not appear to move. Excessive leaking from the top and bottom of the coupling nut. I also tried to just apply a snug tight torque on the coupling nut and it only lasted a few minutes before leaking. This leak has me puzzled and I am out of ideas. I still believe the problem is from the o-ring and crush (compression) orientation.

 

[TractorTech]

Welcome to TBN!

The parts manual shows 9991976 0.070'' Thk x 0.739'' ID 90 Duro. I would look at replacing the fitting as that is where the oring seats and any distortion would come from the track for the oring.

 

[wsand90]

I appreciate the reply. You are correct if the hose is for the output of the front hydraulic pump. My mistake it is a hose for the hydraulic system piping (Center Pivot). Hose part number is 85825187 and o-ring part number is 87016S95. Even if the fitting is incorrect, the 0.614" x 0.070" fits perfectly in the recess area.

 

[TractorTech]

Same oring. 87016S95 is replaced by 9961976 and again, I would suspect the fitting 9621483, about $17.00, at this point. Regardless of the fit of the oring in the recess, it sounds like the fitting has an imperfection allowing the oring to push out of place. The pressure off of the main pump is quite high and receives the most constant load of any line after that.

 

[wsand90]

Good point. It is difficult to inspect the fitting due to its location. Sounds like a plan. Thanks

 

[TractorTech]

I agree, but the hydraulic oil saved will pay for it quickly, not to mention the mess that it is creating.

 

[wsand90]

I believe I know the cause of the problem. I replaced the hose due to leakage through the hose jacket. I replaced the o-ring at the fitting with o-rings that I ordered. When I ordered the o-rings I specified Nitrile/Buna and Duro 90. I found the original invoice and noticed the 0.614 x .070 o-ring was specified with a hardness of NBR 70, which would be inadequate for high pressure applications. I have now ordered the correct o-ring and also the associated fitting. Will try the o-ring first and then progress to the fitting if leakage persists. My oversight may have caused this problem.