In the ongoing crusade to save our engines from their known cooling system failure points, I have the following story.
Driving along recently when I spotted an E46 getting the "helpful shove" of a police cruiser. It was a warm day and I immediately thought "M54 cooling failure." Turned around and found the guy and his dead 325 coupe in a parking lot. Not out of gas, he says. But he did have a leak at the plastic bleeder screw in the upper radiator hose that morning. He zip tied the screw to keep it in place, added some coolant and went to work. Fast forward to that afternoon. Says he drove for about 5 minutes with the temp needle in the danger zone, then the motor just quit. Popped hood, bleeder screw gone, engine devoid of coolant. 120k miles.
Luckily for him he has an extended warranty, which had already been called upon to clean up the mess of his cracked expansion tank some time ago.
Anyhow, when you replace your upper radiator hose, go nuts and spring for the $4 brass bleeder screw. [PelicanParts 17-11-1-712-788-M230]