Coolant Leak: A4 8D Doku, Up to Week 45/1998 (Solution)

Coolant leak at the coolant reservoir.

Cause:
Hose connection between the bleed hose and the expansion tank is not properly connected.
The connector housing for the coolant sensor on the expansion tank is leaking.
Due to a manufacturing defect, the mesh inside the coolant hose is loose. As a result, the coolant leaks out through the vent hose connection to the expansion tank due to capillary action.


Solution:
Replace the hose clamp.
Disconnect the coolant level sensor connector. If there are traces of coolant visible in the connector housing, replace the expansion tank.
If coolant leaks through the fabric of the coolant hose at the connection to the expansion tank, the coolant hose must be replaced.

Sure, here is the translation of the text from German to English:

"Note:"
Coolant traces on the seam of the expansion tank can have the following causes:
- Leak in the hose connection on the vent hose.
- Overfilling of the cooling system, causing coolant to be expelled through the filler cap of the expansion tank.
- The pressure relief valve in the lid is not maintaining the required pressure.