I had to replace my radiator at 100,000 miles due to leaking.. It's my understanding the radiator is expected to fail every 5 years or so.. I also replaced the expansion tank, hoses, and the thermostat and housing.. All were failing as well, as they are plastic parts.
Coolant was dissapearing from tank and dash light kept turning on. After adding the 50/50 coolant/distilled water to the tank, the radiator blew in the front. Do not know the cause, but had the radiator replaced. (so in 20k miles, we've had to have the coolant reservoir, water pump, thermostat, and radiator replaced- that's like the whole coolant system, right?)
My antifreeze light kept coming on and going off . But my coolant was full to the naked eye. After a week or so I noticed that the coolant I was putting into my car was leaking out of the bottom. One day I noticed that the car was smoking from the front, but my engine was never indicating that it was overheating. when I looked to see what was smoking I saw that the coolant was spraying out onto the engine causing some smoke. My mechanic told me that they had to replace my radiator. My baby is currently in the shop.
Apparently there was a hairline crack that was causing the car to overheat. Had to be replaced twice and now after a year we'll be replacing it again. Last time I'll own a BMW.
Leaking coolant after ten minute drive to store on back roads (25 mph)