Nissan Qashqai 2009

The car is a Nissan Qashqai N-Tec1.5 diesel. I paid €3,000 for it and drove it for a year without any problems. Then it stopped accelerating beyond 100 km/h. I took it to a mechanic, and he told me the turbo was the problem. I asked him to fix it. He replaced the turbo with a new one, and I also asked him to prepare the car for the NCT and do everything that was needed. He changed the oil, filters, new tires.In total, I spent €2,000 to make sure everything was in good condition. However, on the very day I picked the car up from the garage, after about 100 km, a metallic noise started coming from the car and white smoke ,the NCT is no longer valid. I.m moving to anhother town so I wont to sell it( battery is dead because I did't turn on the engine in last 3 months)