Hydraulic oil spraying out the fill cap

This may be long but hope someone can help. I am work on and Super M with when purchased had a loader on the front with power supplied via a live pump. High pressure run to a cobbled valve set welded to the light bar and a return was piped back down to the port on the right side of the tractor. The return to the live pump was plumbed from the drain plug by a loose hose under the tractor to the live pump. Looked like crap.

Purchase a control valve from an M with a live pump. Which mounts off the fitting for the fill tube. Ran high pressure supply to the inlet of the valve. Thinking that if system is not operating a plow or something the fluid returns to the belly pump. Also I found the guts had been removed from the belly pump so now just is just a tank. I switched the return line from the drain plug to the same plug that used to be the return from the old valve system noted earlier. To make this work inside the pump I drilled and taped this port and added a tube to about 2 inches from the bottom of the tank.

Worked good until I noticed the belly pump tank is hold press causing some little drips and leaks. I found the vent was plugged and after correcting that problem by removing the screw in it when I started it back up I got a big time spray out of the cap covering everything thing. What should I do know to fix this pressure issue in the tank?

Systems that use one way cylinders (with no Reservoir use of the top half of the cylinder) will need a vent to prevent vacuum and pressure. If the return line can direct fluid toward the cap W/O a deflector, leaks will be tough to stop with the regular cap. JimN

I think you want to take your suction off the bottom, the drain plug being an excellent place. It sounds like you are putting more into your reservoir than you are taking out. There should be no pressure.

Think I am going to reduce the diameter of the pressure side hose. Currently both hoses are the same diameter. Even switching the return down to the drain plug again I am still using the same size fittings to make the connections. I see the origanal designs used 3/4" pressure side hose and 1" suction side hose. will let you know if this works. now I need to go get kiddy litter to clean the mess off the shop floor.

Using the 2-way valve, you should be using a NON-vented fill cap.

Suction should be off the bottom of the belly pump. Return should be through the fill pipe, out the bottom of the 2-way valve.

If I understand you right, you are doing the return to the tank through the fill hole, where the "Christmas Tree" valve is mounted. Since the tank has been gutted it might be best to plumb the return through one of the original pressure ports so the return flow is not flooding the vent connection.

I think you should retain a vent connection.

The top mounted valves are prone to blow liquid out the vent under heavy usage. You may need to run so much fluid in the tank to accomodate the loader that the level is not low enough to avoid blowing a mist out of the vent. When you are lowering the loader you are putting the displacement of the whole volume of the piston end of the cylinders into the vent opening (a lot of flow) while the volume of the rod end of the cylinders is coming out of the suction so the level is rising by the displacement of the rods. A smaller return line to the tank only makes the flow go faster and more likely to retain air.

If you use the loader much in warm weather you might consider adding an auxiliary tank between the drain connection from the tank and the suction to the pump. You can add two gallons of storage easily by making a flat tank to mount to the side of the tractor and gain a lot of hydraulic fluid storage which helps keep the temperature down (and the pressure up). If it is mounted at the same elevation as the belly tank it can have a vent to expel air and if it has flat sides it will radiate a lot of heat which the belly tank cannot do being encapsulated within the cast housing. An auxiliary tank like this can have a few baffles to help get bubbles out of the oil and aid in cooling.