318 hydraulic leak troubleshooting

If leak #1 leaves fluid on the ground, what part of the hydraulic system is directly over the puddle?

Exercising the cylinders with no payload in the bucket may or may not find a leak. Running the cylinders to their limit and holding them there for a few seconds will find the leak.

Leak #2 may be related if the valve set was wet. Implement cylinders hold about 12 cu-in of fluid. If the connection for the 3PH cylinder at the valve set is leaking and you had to raise the 3PH 5 times in an hour because it drifted down, there's your quart of fluid.

If that isn't the source for the leak, most likely the piston seals in the cylinder are worn causing the drift, and the leak is more likely associated with the lines for the bucket hydraulics, including the steel lines under the tractor. Vibration can cause pinholes in steel lines at the clamps.

Murphy has a Law for this stuff. The problem will be with the least accessible component.

Ole Murph and I have been on a first name basis for entirely to-o-o-o-o many years. :hide:

Mmm. Shaky logic. Needs a crash course on Hydraulics 201, Use of multiple valves in an open center system.

With the 3PH valve centered, there is theoretically no flow to or from the cylinder no matter how high the system pressure becomes. In practical terms, any flow to or from the cylinder will be miniscule unless the valve and/or the cylinder piston seals are badly worn.

If you follow the flow diagrams, the fluid travels from the pump to the p/s valve to the loader valve set to the 3PH valve set (assuming that the 3PH valve set is separate from the loader valve set) and back to tank under effectively zero pressure since the system is open center. There is always pressure needed to create flow, but in this case, it's something well under 100 psi.

Higher pressure is required to do actual work when any of the valves are moved off center. In this case, the flow is diverted to a cylinder on the steering, loader, or 3PH which offers resistance to the flow which creates the pressure. The return flow is not normally under pressure and any valves down stream are still under the nominal zero pressure.

When the p/s is activated, the pump sees the pressure required to turn the wheels. Nothing else sees that pressure.

When the loader is activated, the pump and the p/s valve see the pressure required, unless the steering is also engaged, in which case the two pressures are added together and the p/s and the pump see the combined total. At this point, flow may be affected as well.

When the 3PH is activated, the valves that are upstream, as well as the pump, see the pressure required to raise the hitch. Add in the extra info in the previous paragraph.

Should multiple valves be activated at the same time, the fluid will follow the path of least resistance and move the lighter load first. If the combined pressures add up to the relief setting, the relief valve will pop and nothing will move until one of the valves is centered.

Clear as mud?