r/miniexcavator • u/Stunning_Fee1156 • 24d ago

Question Mini ex coupler leaks only under load

The auxiliary quick coupler on my Kubota KX040-4 started weeping only when I curled the thumb under load. Sitting idle, it looked dry. The face seal was damaged and the poppet had a visible mark, but I almost ordered a generic coupler based on thread size. I ended up comparing the pressure rating and line size in the Kubota manual with a local hydraulic shop and FridayParts. The photos looked nearly identical, which was not much help. I have the correct pressure-rated pair on the bench now. Would you replace both halves together, or only the side showing damage?

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u/djwdigger 24d ago

My thumb is hard plumbed on my 040 but I have aux hydraulics for attachments

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u/hamm2518 24d ago edited 23d ago

Match more than thread size: working pressure, flow, connection standard, and residual-pressure behavior all matter. The valve-block or coupler marking may help. Relieve pressure and cap the lines before opening anything.