Fault Phenomenon: SANY SYM5353THB mixer runs smoothly when cold. At high mixing speed (operating temperature), the mixer motor makes abnormal noise, RPM is unstable, and eventually stops.

Troubleshooting Process:
– Checked mixer motor bearings: turns freely by hand, no seizing.
– Checked mixer chain: tension normal, no broken links.
– Checked mixer gearbox: oil level normal, no metal shavings.
– Measured mixer motor inlet pressure at operating temperature: found excessive pressure pulsation.

Root Cause: The mixer motor valve plate deforms due to heat, causing internal leakage and noise.

Required Parts: Mixer motor repair kit.