I bought my Jinma 184 new in 2005; I now have 580 hrs on it and it has been a very reliable workhorse. It has the in-tank screen filter under the seat and I just replaced the hydraulic pump after it started leaking badly. My problem is that it leaks hydro fluid out of the breather vent in the tank filler plug. It has always done this to some extent since new but now it is worse than ever. The rear of the case gets drenched with hydro fluid and leaves a trail of fluid drips and I have to top it off every 20-30 minutes. The filler plug gasket is new and I keep it tight but it just gurgles out of the vent. Any ideas?
If it is spitting fluid out until it gets low about the only thing it could be is introduction of air into the fluid. This would indicate a suction side leak where it is sucking air into the pump. Once the fluid gets back to the tank the pressure drop causes the air to bubble out and that causes foaming which pushes out of the vent tube.
You could try putting a clear hose on the vent tube and run it up along the roll bar so that you can see the fluid. If the tank is simply over full the fluid will be solid but if it is foaming you will see bubbles in the hose.
What indicator are you using for the fill level? On my 284 there is a dipstick in the filler plug (which also contains the vent tube). The dipstick has a grove in it to indicate the fill line. Your 184 may be different. Do you fill the tank with the 3-poing and loader lowered to the ground? If not, it my overflow the tank when you do.