My Astra H 2005 Z18XE engine 30000 Km sometimes makes a thumping noise just after the engine starts.
This lasts just for a couple of seconds and can also be felt by the pedals.
I would say that it does it once every 10 starts and it seems to do it more once the engine is hot. I have never noticed it first thing in the morning.
I've thought that it could be the starter motor not releasing ????
Or maybe that the multi purpose fan belt is too loose too tight ????
Any one had this problem ?
Any Ideas would be welcome ?