The 4620 had a hydraulic oil leak when I started it today, I may have had the engine revs too high when I removed the manual destruction screw from the pump.
The leak is near the manual throttle, between the flywheel and the valve itself … Any ideas? It is a rebuilt valve that was purchased in the US about three years ago and this is the first problem.
It could be an O-ring or worse, a cracked casing … I didn’t even look under the dash hood, but I removed the steering wheel and hand throttle assembly and the oil was coming out of the top with the engine running.
Unscrewing the destruction screw at high speed did not cause leakage. The top seal failed and the valve needs a seal kit. The seals can be replaced without a dyno as many have been resealed without one. The only problem is that proper operation and no leakage will not be established until after the valve is reinstalled on the tractor, unlike on a test bench.
The O-ring and backup washer (key parts 18 and 19) is where the problem is. Valve adjustment requires a special plate and dial indicator. I’m not sure it can be resealed without altering the valve settings.
Most likely, the # 19 o-ring is worn and allows oil to run up the shaft and overload the # 9 gasket.