The underfloor CNG tanks are exposed to external influences that can lead to reduced durability. The gas bottles must therefore be regularly checked in accordance with the Volkswagen servicing schedules. Any corroded gas tanks can then be replaced without delay. If the inspection of the gas system is not done or is not done precisely, any corrosion of the bottles may remain undetected.
This creates the risk that in some of these vehicles a damaged outer casing no longer provides the necessary protection from corrosion. Ongoing corrosion leads to a continual reduction in the thickness of the wall. If the residual wall is too thin, that can lead to a gas tank bursting.
In Germany a standardised check of the complete gas system performed in accordance with the ECE standard has been carried out since December 2014 during the main vehicle inspection. Differing rules govern the specifications for regular checks in the import countries.
The owners of the vehicles are being written to directly by Volkswagen and asked to make an appointment with their authorised workshop for the gas tank to be replaced. All affected Touran customers of model years 2006 to 2009 are also being advised in this letter that as a precaution their vehicles should only be used in petrol mode until the work has been done.