During this investigation, Volkswagen of America (VW) identified a problem with water accumulation in the fresh air plenum that could, in certain circumstances, result in reduced brake power assist in model year (MY) 2002 Passat vehicles.VW indicated that problem is caused by leaves and other debris clogging the plenum drains, which may result in water filling the plenum to the level of the brake booster air intake.the booster air intake is located in the fresh air plenum in the MY 2002 Passat vehicles, but not in the MY 2001 or 2003 vehicles which draw booster air from the cabin.VW testing showed that brake assist could be reduced if water enters the booster and freezes.VW is addressing the problem with a service campaign, which began in August 2007.the fresh air plenum in the subject vehicles is an enclosed space at the base of the windshield from which the vehicle ventilation system draws the fresh air supply via a pollen filter.rain water that flows off the windshield into the plenum is drained through two valves located below the battery and brake booster.strainers at the base of the windshield and in the panel covering the top of the plenum block leaves, pine needles and other debris.over time, debris may enter the plenum through openings in the plenum panel or around the hood hinges.if clogged drains allow approximately 3-4 gallons of water to accumulate in the plenum, the water may enter the booster through the air intake.water accumulation in the plenum may also result in complaints of wet carpets in the vehicle interior if the water reaches the level of the fresh air intake/pollen filter. VW stated that its testing showed that brake performance and actuating force (I.e., pedal effort) are not affected when the booster is filled with the maximum amount of water possible (up to the height of the booster engine vacuum connection, through which water drawn into the booster is evacuated).VW's testing showed that brake performance and actuating force could be affected by water freezing in the booster.however, when tested with relatively low volumes of frozen water in the booster, VW showed that the effects were significantly less severe than for conditions that result in a complete loss of vacuum assist.while VW indicated that the effects would be more severe with greater volumes of frozen water, it maintained that the chances of this occurring were remote and would be readily discernable to the driver upon the initial brake application after vehicle start-up.ODI's analysis of complaints and warranty data showed disproportionate concentrations in winter months and in northern states with colder winter climates. ODI identified three minor crashes related to the alleged defect in MY 2002 Passat vehicles.two of the crashes occurred ingarages/driveways and the third occurred in a dealer service garage.there were no injuries alleged in the crashes but a foot injury was alleged in a fourth incident where excessive brake effort required during a hard stop. Volkswagen is conducting a service campaign to remedy this condition in MY 2002 Passat and Audi A4 and A6 vehicles.the remedy procedure requires VW dealers to inspect, clean and modify the air plenum drain, as well as modify the sunroof drain (if equipped) and install an improved seal for the pollen filter.in addition, VW has agreed to provide the following information to odi1. Quarterly completion reports for one year; and 2. promptly reporting all crashes attributed to the alleged defect. This investigation is closed based upon the actions taken by VW.the closing of this investigation does not C
