Hydraulic oil mix with Transmission oil Hitachi ZW180

[md_siam]

Hey everyone,
For a long time i am facing a issue with my HITACHI Wheel Loader ZW-180. The problem is hydraulic level goes down and transmission level goes up. I have changed the main hydraulic oil seal several time. But no improvements. After changing the main oil seal, when we operate the machine there is no problem of mixing. But when the machine is in stop condition, like it's parked the hydraulic level go down and transmission level go up. Recently (approximately 20-30 days before) i took support from the concern dealer of my country. The checked our machine and changed one bearing and main oil seal of hydraulic pump. But again my machine is parked for last 3 days for holiday and today i found my hydraulic level is down and transmission level is up.

Can i get some suggestion with this problem?

Thanks.

 

[miketurner]

Based on what you’ve described, it seems likely that the hydraulic oil is leaking into the transmission through a shared pathway, possibly due to pressure equalization when the machine is parked.
I was searching online here some of reasons for it

1. Pump Casing or Housing: Even if the seal has been replaced, there could be a hairline crack or wear in the pump casing that's allowing hydraulic oil to seep through when the system is at rest. This is something that might not show up during active operation.
2. Check Valve or Relief Valve: A faulty check or relief valve could allow hydraulic oil to backflow into the transmission, particularly when the machine is off and pressures stabilize.
3. Seals on the Transmission Side: If there’s a seal failure on the transmission side of the pump, it could create a pathway for oil to migrate. Even with a good hydraulic seal, the transmission could be pulling oil in when the machine cools down.
4. Pressure Imbalances: When the system is off, pressure changes in the hydraulic system could force oil into the transmission if there’s a weak spot or connection between the two systems.

 

[md_siam]

Based on what you’ve described, it seems likely that the hydraulic oil is leaking into the transmission through a shared pathway, possibly due to pressure equalization when the machine is parked.
I was searching online here some of reasons for it

1. Pump Casing or Housing: Even if the seal has been replaced, there could be a hairline crack or wear in the pump casing that's allowing hydraulic oil to seep through when the system is at rest. This is something that might not show up during active operation.
2. Check Valve or Relief Valve: A faulty check or relief valve could allow hydraulic oil to backflow into the transmission, particularly when the machine is off and pressures stabilize.
3. Seals on the Transmission Side: If there’s a seal failure on the transmission side of the pump, it could create a pathway for oil to migrate. Even with a good hydraulic seal, the transmission could be pulling oil in when the machine cools down.
4. Pressure Imbalances: When the system is off, pressure changes in the hydraulic system could force oil into the transmission if there’s a weak spot or connection between the two systems.

Thanks for the suggestion. I will look after it.