Hi folks i am selling my car ( 1998 VAUXHALL ASTRA LS 8V BURGUNDY NEW SHAPE )?

and today i had a bloke come and view her, i had her running and he went to his car and got a bottle of coke and put it to the engine and had the coke to his ear, and then went to the back of the car and done the same, i dare say them maybe method in his madness but can any help and tell me why he done this ,i am no car buff but my car is in mint condition and i just wonder why this man done this cheers for your help xx