Click here to enlarge Originally Posted by Arkos Click here to enlarge
Hey man i think i have the same problem. My mechanic said that it is the oil pressure being taken up to the required level. He also said that all Astras sound like that. Here is a video link, hopefully someone more knowledgable can shine some light on this problem.

https://www.youtube.com/watch?v=YDM2fl7fnQA
yours is the chain tensioner making noise.