Off late I could see that whenever I am using AC, the engine seems to be strugling and the mileage drastically decreases. There is no problem with the cooling efficiency of the AC. I could also see that water is leaking below the radiator whenever AC is on. But once I switch off the AC, the leakage also stops. There is no drop in the coolant level as well. There is an increased noise and vibration when AC is ON. But thats usual right? What could be wrong here?