Richard
I thought I put some photos of that install in this thread where I described the install of a return line filter on my Backhoe, but I just looked and there are not any of the new return port on the backhoe tank.
http://www.tractorbynet.com/forums/chinese-tractors/111225-jinma-hw03-backhoe-return-filter-2.html
Here are a few:
Basically what I did was get a 3/8" steel street elbow and ground out the threads and some of the internal wall with a die grinder. I welded the big end of this over the threaded return bung on the side of the resovoir. I had already increased the size of the return hose to 1/2" from the filter I installed(detailed in the above link), and this hose slips right over the small end of the street elbow and is held inplace with a hose clamp. Here is a pic of where the other end of the red hose is attached to.
I had to do this mod as this addon filter was experiencing some wicked pressure spikes. I blew the filter "O" ring out at one point from the pressure caused by the tank banjo fitting and the small diameter hose. But in my testing to fix the filter pressure issues, I also discovered that it shuts the pump noise right up. That was when I figured out what was going on with the pump getting air in it's supply oil. The BH pump is basically the same as the main tractor hydro pump, and that one dosn't make any noise does it?
To do the elbow mod to the tank like I have done, The return hose from the backhoe valve tothe tank could be replaced quite easilly with larger hose using the end fitting of the existing return hose up at the vave end and cutting off the rest. Or you could put together a metric adapter for the outlet/return port on the valve and run a larger hose from it if you didn't want to cut up the original hose. I believed the chinese just used an off the shelf hose from some other production to fit this space. The stock hose on mine was pressure rated, and only a 10MM ID. The return hose does not need to be pressure rated as it should only ever see a few PSI. They are typically also 1.5X the supply line diameter...
As for the resovoir overflowing, that is caused by the way they did that filler neck tube. It protrudes down into the resovoir, in an attempt to keep you from overfilling the resovoir I assume. But if you fill it up to top of the port on the filler neck, as the fluid expands, it covers this filler port and pressurizes the air space in the top of the tank. This pressure forces the fluid up thru the filler neck and out the vent hole. One simple way to prevent this is to remove the screw in dipstick. This keeps any pressure from building in the top of the tank as the fluid expands. But it leaves a pathway for dirt and water to enter the tank. I converted my dipstick port to the air vent and have a filter on that port. I sealed the vent holes in the screw on cap. The protruding filler neck is now my level check. I just remove the filler cap and look down the hole to see where the fluid level is in relation to the lower end of the filler neck. No more oil burps
Here is a pic of my breather filter. It is a basic in-line fuel filter available at just about any auto parts store. I used a couple of pieces of hose to adapt it to the dipstick neck. On the top is a rubber vacume port end cap from the same autoparts store, with a couple of small holes drilled into it to allow airflow. I poured indicating dessicant thru the end port to fill the area around the outside of the filter element. This helps control the moisture content in the tank as it breathes. It should be blue, but as it is pink, it is saturated from mosture and needs to be renewed(shake the pellets out, microwave till bright cobalt blue, and pour them back into the filter).
