Irritating rattling noise from the vehicle underbody

In this repair case, the customer complained that their Audi A4 1.8 16V TFSI (model year 2012-2015, engine code CJEB) had developed a very irritating rattling noise in the vehicle underbody area.

The noise only occurred temporarily, whilst the vehicle was being driven, which made troubleshooting the cause more difficult for the workshop.  

The solution
During troubleshooting by the workshop, the cause was determined to be the heat shield of the central silencer.
The heat shield was inadvertently making contact with the body, depending on the vehicle vibrations and the vehicle underbody temperature.

Repair tip
To eliminate the problem, remove the heat shield of the central silencer (see second figure above) as instructed by the vehicle manufacturer. Carefully clean the area highlighted in the figure (approx. 50 mm x 50 mm), and then apply an adhesive agent suitable for use in this area (e.g. heat-resistant body adhesive) in a layer approx. 5 mm thick onto the cleaned surface.

Then install the heat shield again, press against the area that you have just prepared with the adhesive, and fix it in place until the adhesive agent has cured.