Mysterious Hydraulic leak

Mikeyp756 · May 23, 2019

Hay guys, I mentioned this before now I’m just getting back to it. On my Hitachi Ex120-2 I have a bad “hydraulic fluid” leak. Not gear oil. Fluid is coming out between the swing bearing. When I got under the machine it was dry. I saw a small what I would call an inspection plate with 2 bolts. When I removed it clean hydraulic fluid poured out. And I could see the swing/bearing gear. I’m assuming it’s from a seal in the swing motor but not sure which part. Has anyone ever seen this?

uffex · May 24, 2019

Good day there are a couple of possibilities if the swing motor passes fluid into the transmission then on it could appear in the swing ring check to see what oil you have in the transmission, the other possibility is that of the central joint.
kind regards
Uffex

mg2361 · May 24, 2019

If your swing gear box is full then it is your rotary manifold that is leaking.

Mikeyp756 · May 24, 2019

mg2361 said:
If your swing gear box is full then it is your rotary manifold that is leaking.

Thanks mg2361 I guess you mean the swing motor. I’m thinking that’s the only thing that can leak hydraulic fluid there. But I’m trying to figure out which section of swing motor would be leaking.

Ronsii · May 24, 2019

More than likely the rotary manifold(central joint) that is leaking, NOT the swing motor, the rotary manifold is in front of the swingmotor/gearbox about a foot or so... have you pulled the bottom cover plate from the undercarriage?

Mikeyp756 · May 24, 2019

Ronsii said:
More than likely the rotary manifold(central joint) that is leaking NOT the swing motor, the rotary manifold is in front of the swingmotor/gearbox about a foot or so... have you pulled the bottom cover plate from the undercarriage?

You mean the rotary manifold for the travel? I can’t see how the rotary manifold can leak at the swing bearing.

Ronsii · May 24, 2019

They do....

if you pop the plate off underneath it you'll know for sure.

Mikeyp756 · May 24, 2019

Ronsii said:
They do.... if you pop the plate off underneath it you'll know for sure.

I did look underneath. It’s all open. I opened small plate with 2 bolts where you can see the swing gear and fluid poured out.

Ronsii · May 24, 2019

When you looked under there what did the manifold look like and it's hoses?

Also, the question in post #3 was asked but you haven't mentioned if the swing motor gearbox was full on the dipstick or not?

Mikeyp756 · May 24, 2019

Ronsii said:
When you looked under there what did the manifold look like and it's hoses?

Also, the question in post #3 was asked but you haven't mentioned if the swing motor gearbox was full on the dipstick or not?

There were some small drips on the fittings dripping on the ground. The gearbox is full with gear oil. The problem is leaking hydraulic fluid.

mg2361 · May 24, 2019

The rotary manifold (yes, for the travel) can leak from the top under the main frame which is under the rubber boot that you see looking down from the top. When it leaks it runs into the swing gear grease bath until it fills the cavity then finds it way through the swing bearing....which then you see. Since you said the gear box is full then it is your rotary manifold.

92U 3406 · May 24, 2019

The EX series was before my time but I seem to recall that they use gear oil in the swing box, so unless the swing motor seal grenaded at the same time the swing gearbox seal crapped out the only way you'll see hydraulic oil in the centre tub is if the rotary manifold is leaking.

Mikeyp756 · May 24, 2019

mg2361 said:
The rotary manifold (yes, for the travel) can leak from the top under the main frame which is under the rubber boot that you see looking down from the top. When it leaks it runs into the swing gear grease bath until it fills the cavity then finds it way through the swing bearing....which then you see. Since you said the gear box is full then it is your rotary manifold.

Well it definitely sounds like it the way you describe it. I thought the rotary manifold was mounted too low to leak there. I’m not sure where the rubber boot you refer of is. So I have to drop the rotary manifold?

excavator · May 24, 2019

If you are here asking about this then please listen to those who are trying to help you. You asked about this a month or so back and were advised that the rotary manifold is likely leaking and that is still the problem you have today. You likely will not see any oil looking at it from the bottom because that is not where it is leaking. It leaks where the center shaft goes into the rotary housing, which when it is in the machine is just below the floor of the car body. So as mg2361 said, it will fill the swing bearing grease bath area and leak out the swing bearing. If you stand in front of your machine and look between the boom cylinders you will see 4 hoses going to the rotary just above the car body floor. There is a flat rubber boot around the rotary that seals between it and the floor.

Mikeyp756 · May 24, 2019

excavator said:
If you are here asking about this then please listen to those who are trying to help you. You asked about this a month or so back and were advised that the rotary manifold is likely leaking and that is still the problem you have today. You likely will not see any oil looking at it from the bottom because that is not where it is leaking. It leaks where the center shaft goes into the rotary housing, which when it is in the machine is just below the floor of the car body. So as mg2361 said, it will fill the swing bearing grease bath area and leak out the swing bearing. If you stand in front of your machine and look between the boom cylinders you will see 4 hoses going to the rotary just above the car body floor. There is a flat rubber boot around the rotary that seals between it and the floor.

Just trying to make sure I’m understood and understand what to do next. Sorry to bother you.

Mikeyp756 · May 24, 2019

Mikeyp756 said:
Just trying to make sure I’m understood and understand what to do next. Sorry to bother you.

I guess my time ran out about asking about the machine bogging down under a load too.

mg2361 · May 25, 2019

Check all controller fuses, especially the 1 amp F7 fuse. If all the fuses are good try swapping the two solenoid valve assemblies on top of your pump. If the problem becomes weak hydraulics then one of the solenoids are bad.

Mikeyp756 · May 25, 2019

mg2361 said:
Check all controller fuses, especially the 1 amp F7 fuse. If all the fuses are good try swapping the two solenoid valve assemblies on top of your pump. If the problem becomes weak hydraulics then one of the solenoids are bad.

Thank you mg2361, I did find 1 solenoid bad and replaced both. Now no fuses blow. But still bogging. Could it have to do with throttle being disconnected. It’s had the throttle lever since I got the machine. Thanks

Mikeyp756 · May 25, 2019

Mikeyp756 said:
Thank you mg2361, I did find 1 solenoid bad and replaced both. Now no fuses blow. But still bogging. Could it have to do with throttle being disconnected. It’s had the throttle lever since I got the machine. Thanks

Oh now I realize the detached cable is for engine stop.

mg2361 · May 26, 2019

Engine sound? Need to rule that out first. Fuel filters, fuel supply, fuel quality? Stop lever on injection pump all the way on? Can boost pressure be obtained?

Mysterious Hydraulic leak

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