One problem related to coolant leaking has been reported for the 2005 Audi A4. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2005 Audi A4 based on all problems reported for the 2005 A4.
2005 Audi A4 avant is currently still under warranty but the Audi dealership and Audi of America will not replace a cracked coolant reservoir. The onboard computer came on, indicating a problem, but there was no leak. However, the crack was very visible and will most likely spread further resulting in a leak. The crack was most likely caused from the excessive heat under the engine hood. I believe this was a serious flaw in materials used to manufacture the reservoir.