You can pursue a claim for negligence for up to 6 years after the relevant act (or for up to 6 years from the date when the negligence became apparent).
So if your friend, say, failed to properly secure some nuts (by, for example, fitting locking nuts) and something dropped off the car two years later (having gradually worked itself loose over that period of time) then he could be pursued for the cost of any damage or injury resulting from his negligence.
However, other than such a claim for negligence (which would seem not to be what is being alleged) the car owner hasn't got a moggy-in-Hades chance of winning a court action against your friend.