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318 hydraulic leak troubleshooting

3758 Views 12 Replies 3 Participants Last post by  PED
Need some help troubleshooting 2 hydraulic leaks. These leaks showed up when I started using my new Buford Bucket and 3 point weight bucket.
Leak #1 leaves fluid on the ground when I park it. No much so I think the leak is mainly when I am actively using the front bucket. It lost about 1 qt of fluid after 1 hour of bucket use. It is not leaking at the filter or any of the hose hook up connectors. The underside of the control unit was wet so I wiped it down to see if I could see evidence of a leak. I exercised the hydraulics a few times and then shut it down. Nothing showed up while sitting still so I will need to check it more closely after using the bucket for a few minutes.
Leak #2 is related to my 3 point hitch with a weight bucket on it. Will not stay in up position. Over a few minutes, the weight bucket will drop to lowest position. No external evidence of a rock shaft cylinder external leak so I am guessing it is an internal leak somewhere.
Do not know if leak #1 and #2 are related or if they showed up when I started using hydraulics not previously use until I installed the bucket and 3 point.

Another "difference" is that I sometimes have a bit of forward creep now even when the control lever is in neutral. Did not have that previously. Can a low fluid condition cause that?

Any suggestion on trouble shooting this problem? I hate that thought of tearing everything apart to work on the hydraulic control unit since everything else is in the way.
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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:
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The leak is very close to the valve set. That is the wet area and appears to be the source of fluid. I am hoping that both leaks are related. If the leak is one of the connections to the valve set, is it just a matter of tightening up the connections (assuming it is not a pin hole in a tube)?
I suspect this leak has been around since I bought this 318 because that area was very dirty and had collected a lot of oil/dirt. However, it did not show up as a major issue until I added the front bucket and weight via 3PH to jack up the pressure on those lines.
I can lift the front bucket and it will hold. However, if I lift weight with the 3PH, it will leak back down. As a result, I suspect the leak is in the lines to the rock shaft cylinder. I will load up some weight on the 3PH and see if that shows up a leak.
The 3PH cylinder operates on the wrong end of a 4 or 5:1 lever, ie. 200 lb on the 3PH equals 300-400 psi in the 2" cylinder, and therefore the lines back to the valve set.

Probably a loose or cracked fitting on the valve set is the cause.
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?
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A crows foot wrench won't fit either. Either a flare nut wrench, or remove one line that is easier to get to so that there is more room for dealing with the offending fitting.

I usually use a combination wrench.
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