There have been complaints of an engine noise at start-up on some 1999-2005 Volkswagen 1.8, 2.8 and 4.2L engines. Volkswagen AG has issued the following information regarding this condition.
A condition may exist between the valve train components, camshaft chain tensioner(s), or camshaft adjuster(s) during start-up, creating a rattle or knocking noise.
The camshaft adjustment is hydraulically actuated and controlled by the engine oil pressure. If the vehicle has been sitting, with the engine turned off for a period of time, the oil accumulation inside the camshaft adjusters partially bleeds off and the oil flows back into the oil sump.
To ensure an efficient camshaft adjustment after an engine cold start, the oil pressure inside the camshaft adjusters must be built up as quickly as possible. During this time a slight rattle or knocking noise may be audible. This noise is normal at engine start-up and will last until the oil pressure is fully reinstated.
DO NOT replace the Camshaft Tensioner(s) or Camshaft Adjuster(s) for the noise concern as described above.
Replacing the Camshaft Tensioner(s) or Camshaft Adjuster(s) will not eliminate this noise on these engines.
This information was brought to you by the Engine Rebuilders Association (AERA).