BMWs are great cars for the most part. Their performance per pound make them a serious competitor in the market for people that want a thrilling driving experience. But they do have an achilles heel: The cooling system. As the system is sealed, meaning that there's nowhere to bleed off air when in normal running condition, bleeding the system properly is one of the most important things you can do to keep your car running for years to come. Here's how to do it, the right way.