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The draft arms are held in the raised position by a hydraulic lock on the cylinder. Leak down occurs if there is leakage pass the piston and /or through valves in the control block. Check for piston leak by disconnecting the leak-off tube fitting. It is normal to find grease & some residual oil drip here. Work hitch until cleared and drip stops. Lift & hold a weight and observe the leak off. The control block has 4 valves: 1) lift valve, 2) lift check valve, 3) release valve, 4) relief valve. Think of the hyd lifting circuit as a �T�. Pump pressure at the bottom, lift check valve upper left, and lift valve upper right. Lever in neutral: pump input is circulated back to the sump by the open lift valve, all other valves are closed. Lever in raise position: lift valve is closed by the cam, press builds up in the �T� forcing open the lift check valve and admitting oil to the cylinder. At the desired height, lever is returned to neutral. Lift valve, opened by its spring, by-passes pump press to sump again. As press drops in the �T� the lift check valve is closed by its spring. The cylinder is now held in a hyd lock by the lift check valve, relief valve, and the release valve. Lever in lower position: The release valve is opened by the cam dumping trapped oil into the return passage. The lift check valve is located under the plug on the bottom of the control block. The other 3 valves are on the right side of the block under the cam.
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