hi all got another problem my car runs and drives fine but after half hour or so of driving if I turn engine off ie go shop start it back up it starts to rattle it sounds like a bike chain being shook by hand from cylinder head but if I turn it back off leave it ten min its fine again is it signs of cam chain tensioner on its way out any help would be greatfull just had service 5w40 fully syn its 2001 a4 1.8t 90k miles