Fault Phenomenon: Putzmeister M52 lubrication functions normally when cold. During continuous pumping (operating temperature), a lubrication alarm sounds, the distributor does not actuate, and the machine eventually stops.

Troubleshooting Process:
– Checked lubricating grease: not hardened.
– Checked lubrication pump motor: motor runs normally.
– Checked pressure switch: switch setting correct.
– Measured lubrication line pressure at operating temperature: found pressure cannot be built up.

Root Cause: The internal check valve of the lubrication pump sticks due to heat, preventing pressure build-up.

Required Parts: Lubrication pump check valve or pump assembly.