How can I repair a small leak the radiator and is my fan belt drive or electric on 1993 BMW 740i

My car out of the blue starting running hot

Asked by for the 1993 BMW 740i
Given the fact that your radiator plays such an important roll in keeping the engine/transmission oil properly cooled. I would NOT repair radiator. I would replace it. Worst case scenario (engine failure) is too expensive to attempt to save on a radiator cost replacement. Your vehicle has both mechanical hydraulic fan clutch (main engine cooling fan) & an electrical auxiliary fan that works w/ air conditioning and as a secondary back up cooling fan if primary were to fail. Good luck.