Last weekend I changed the coolant on my 2006 M3 at a club DIY event. BMW of Sterling was our gracious host for the event, giving us access to its large and state-of-the-art facility.
I had done the same maintenance in 2018 at Sterling. I went in hoping I could again borrow a fluid exchange machine that makes the process a lot simpler and cleaner. I was ready if the machine was not available, having found an excellent video from enthusiast owner Blue Purple Red on the old-school method. The machine saves a lot of time and eliminates the need to remove a drain plug on the side of the engine block.
Sterling technician Chris set me up with the machine and explained the settings. He was extremely helpful to me and the other club members. DIY techs are not there to do the job for you, but it’s reassuring knowing you can ask a pro when unexpected issues arise. And often they are old-school enthusiasts like us.
I also replaced the coolant temperature sensor that sits on top of the radiator hose. I bought it for prophylactic reasons a while back, but when I did the coolant change I noticed some dried coolant around the sensor suggesting a small leak had developed. The sensor put up a battle before coming loose, being almost certainly original and over 18 years old.
The stock bleeder screw used during an E46 M3 coolant change is plastic. I replaced it with a bronze screw because that just says conscientious owner. However, I didn’t need the screw since the fluid exchange machine maintains the pressure in the system as the fluids are exchanged. So this simultaneously acts as a leak test for the coolant system.
The coolant is good for at least two years. Another important maintenance item checked off thanks to the National Capital Chapter DIY program. Happy Motoring!