Oh dear. Persevere though. Our son had a leak in his car, only knew as he was always topping up the oil, but no tell tale puddles. He had knocking noise too. Garage could never find anything wrong. So he went online & discovered it was common problem with this make. It was still under warranty, so he got in touch with manufacturer, Seat, they said it should be fixed under warranty. Garage kept putting him off, warranty was about to run out & obviously couldn't be bothered putting in the time. However, he persevered & it's now fixed, no charge!