Vehicular Hypochondria
A mechanical condition where your car leaks fluids, blows smoke, and makes horrible noises...until you take it to the shop and the mechanic can't find anything wrong with your vehicle. After spending $45 an hour for a diagnostic check which revealed nothing, the vehicle runs perfect.
Customer: "The Check-Engine Light and Service Engine Soon Light both came on. I smelled a burning smell, like something electrical. Then there was this grinding noise on the right side."

Mechanic: "I drove it around for 30 minutes and I didn't hear or smell anything. If you notice anything, bring it back and we'll deduct the price of today's service from the repair."

Customer: "I think my car's suffering from Vehicular Hypochondria! I swear it sounded like it was going to die! Now it's perfect. Go figure!"