Most hydraulic valves, called "Spool Valves", because they look like old time thread spools,are precision machined, and then "Lapped in" to a precision fit. Spools are not normally interchange -able in any one valve body, or even between the same make and model of valve. (There are some exceptions now, where the spools, and bodies are machined with such precision, that they are not lapped)Valves hold hydraulic pressure by the metal to metal fit. There are no O-rings in everyday valves,except at the ends of the spools, to prevent external leakage, If your system is "leaking down" it may be that the valve is worn out, and must be replaced,(I know of no maker that sells replacement spools), or more likely the cylinder seals, or packings, are worn out from back and forth motion. (Seal wear avoids metal to metal wear, in cylinders, which is much more expensive to repair) Another note: Hydraulic motors, (Think: Char-Lynn) have a definite "Life" and can have internal leakage. Your valve has no "Missing O-Rings", but is likely leaking down due to internal wear! On Giant excavators, and power shovels, such as used in open pit coal mines--where the buckets are large enough to hold a pickup truck, the valves weigh several hundred pounds, and cost thousands of dollars, and are indeed rebuilt, by the "Spray Welding" process, and remachined, usually they are returned to the factory for that.
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Today's Featured Article - Identifying Tractor Noises - by Curtis Von Fange. Listening To Your Tractor : Part 3 - In this series we are continuing to learn the fine art of listening to our tractor in hopes of keeping it running longer. One particularly important facet is to hear and identify the particular noises that our
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