Why is my Audi A4 Avant leaking into the driver's side floor well?

In April this year I bought an Audi A4 Avant SE 2.0, first registered 29-09-2010. We then had a dry summer and it wasn't until heavy rain in early August that I found the floor mats on the drivers side and off side rear floor well soaked. The dealer was obliging and had the car for a week to dry it out and fix the leak. They found that the drain from the ventilation system was blocked with leaves. They cleared the drain and after an alleged successful water test claimed to have fixed the fault. The work was covered by the warranty. A fortnight ago we once again had rain and the same fault occurred. The car is going back in next week for further investigation. Do you have any information on similar problems with A4s?

Asked on 30 November 2013 by DP, St. Austell

Answered by Honest John
Historically this used to be common on A4s and Passats. But when it happened to me, in a SEAT Leon 20VT just after a service, it was because the replacement pollen filter had not been fitted correctly (it's a very fiddly job on a RHD VAG car). That might be the reason for your latest flood. Another possible reason is failed waterproof membranes inside the doors.
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