When your coolant temperature sensor fails, it can sometimes forget to tell your radiator fan to turn on.
When your radiator fan doesn't turn on, the coolant generally overheats.
When your coolant overheats too much, it can crack your radiator and ruin the pump.
Believe me. I ought to know.
So, while they were fixing Otto up with a new radiator, etc., they pointed out that the timing belt was due for a change. Well, was going to have to happen sooner or later. Sure, why not now, while he's already in various stages of disassembly?
With the engine out for the timing belt change, they noticed a cracked engine mount. Ooooh, so THAT's what that rattling sound was when I was stopped at stop lights.
With the damage repaired, or the damage done, depending on the damage you speak of, Otto came home with a NEW strange rattle. So the next day he went back to the doctor, to find that an exhaust clamp had slipped loose, but was repaired easily enough, and for free. Unlike the other repairs!
So now my Otto is no longer an overheating rattletrap of a little white car. He runs smoothly and quietly, and is perfectly content!
Except for the intermittent hiss of the air conditioner compressor valves slowly going out.
But that's another story, for another time.