What Are the Signs of a Failing Auxiliary Pump 04L965567A in Your Audi?

When the Audi 04L965567A auxiliary cooling water pump fails, the following typical signs may be shown, and a comprehensive judgment is required based on the system function and mechanical characteristics:
1. Signs related to direct functional failure
1. No cooling cycle after shutdown
After the engine is turned off, the sound of the auxiliary pump cannot be heard. Under normal circumstances, it should continue to run for 5-10 minutes and make a slight "buzzing" sound.
The turbocharger area has obvious high temperature after the combustion is turned off. You can feel abnormal heat by hand or smell the scent of burnt coolant/engine oil.
2. The cooling system warning light is on
The dashboard has a warning light of "Engine overheating" or "Cooling System Error", which is triggered especially when driving at high speed or when the engine is turned off after heavy load.
2. Signs of abnormal mechanical/electronic components
3. Auxiliary pump sounds
It makes a sharp "squeak" sound when running, and it makes a low "roar" sound, especially during the operation stage after the engine is turned off.
4. Coolant leak
Coolant leakage occurs at the auxiliary pump body or connecting pipe. Audi coolant is usually red/pink. If it leaks, the liquid level will drop faster. You need to check the auxiliary water tank regularly.
Leakage causes: aging of the pump body seal ring and cracks in the plastic shell.
3. Indirect impact and derivative problems
5. The turbocharger is damaged
Long-term failure of auxiliary pumps will cause the turbine shaft center to stagnate or burn due to poor high temperature lubrication.
Severe carbon deposits can be seen when dismantling and inspecting the turbine.
6. Engine performance deteriorates
To protect the engine, the ECU may trigger "limp mode" or may experience cold start difficulties.
4. Troubleshooting Suggestions
Simple verification: After turning off the engine compartment, open the engine compartment and touch the auxiliary pump body with your hands. If the temperature does not rise, it means the pump is not working.
Diagnosis priority: Check the operating status and fault code of the auxiliary pump through Audi's special diagnostic instrument, which is more accurate than direct replacement.
Correlation inspection: If the auxiliary pump fails, the cooling liquid quality, circuit connection and relay/fuse need to be checked simultaneously.