I wish I could listen to other 603's to see what's "normal". The truth is I've been battling what I've thought to be a knock on my 603 for almost a year and I haven't won. Shortly before I rebuilt my injectors there were occasions when there would be no knock. Afterward it's been constantly there just like when I first bought the car. The only time the engine sounds totally smooth is when it's running on Diesel Purge. My question is, does your 603 knock? Or does mine really have some sickness?

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL