well, basically the chap he sold it to is trying to pull a fast one, it was sold through ebay as needing work for £500 and the buyer is now saying it needs around £7-800 spent to sort the steering and braking systems out! my friend was as honest as possible with the buyer and he went away happy but came back a few days ago saying its going to go through the courts etc etc as the car is unfit for purpose! My friend has offered to help out with costs slightly if he takes it to a local dealer to diagnose the issues but the buyer isnt keen on that and just want cash up front!....
Provided your mate was as honest as possible during the transaction of the car and listed the faults as he knew them, then the buyer doesn't have a leg to stand on. Also it seems weird that the guy isn't prepared to get the car checked out by a qualified dealer. If he wanted to take your mate to court he'd have to be able to show that your mate misled him in some way and in order to do that would have to evidence his findings i.e through a qualified dealer.
You should tell your mate that the next time the buyer contacts him demanding money that he will be breaking off communication with him and that if he would like to take you to court then to go through the proper channels. Also that if he calls again after that then you will be informing the police as this is harassment.
Point of interest: This is a well known scam. There are people that will buy cheap cars, then harass the seller claiming that the vehicle is faulty in some way and attempt to get back more than they paid for it in the first place.Then selling the car on making a tidy profit. These people can be really pushy and even threatening. So if you feel this is the case call the police and get there advise.
Hope this helps.
Andy