Fault Phenomenon: Schwing S700 tank is normal when cold. During high-flow return (operating temperature), the hydraulic tank collapses, the pump cavitates, and eventually fails.

Troubleshooting Process:
– Checked tank cap breather: vent unobstructed.
– Checked return filter: filter not clogged.
– Checked tank structure: no deformation.
– Measured internal vacuum of the tank at operating temperature: found excessive vacuum.

Root Cause: The tank breather is frozen or blocked, causing internal negative pressure and tank collapse.

Required Parts: Tank breather and tank repair.