Lift Arms Rise, Dont Fall

I was using a 60″ finish mower attached to my ’53 TEA 20 when for no apparent reason the hydraulic arms lifted up to max height, and would not come down.  They came down slowly when the engine was shut down, and rose up completely when the engine restarted.  Can you tell me what might be causing this?  September 2, 2016.

I suspect the control valve “dog bone” segment has become disconnected from the two vertical levers that move it in and out to control the lift, and lower functions. Remove the right side access cover, the cover that has the transmission/rear end dipstick in it. With the tractor turned off, move the hydraulic lever, ok and observe the vertical control levers move forward and back. Follow the levers down into the oil and feel both sides to check if both sides are connected to the “dog bone”. The dog bone is sort of cylindrical with a ball on each end. Both ends should be seated in the sockets at the end of the vertical levers. Also check to make sure the valve, a cylindrical shaped piece approximately 5/8″ in diameter is still moving in and out of the bore in the control valve. It is also possible for the cylindrical piece to hyperextend, and pull out of the bore. Still another possibility is the small rod that connects the cylindrical piece to the dog bone. That rod is attached to the dog bone with a small hair pin fastener. If the pin comes out the valve will stay in whatever position it was left in.

There are some other possibilities but check these first. The others are a little less likely, and harder to check out.