· OEM ///PLUS
2003 M3 6MT Slicktop
sounds like the bleeder screw which is plastic either broke or was leaking. causing the system to not be pressurized and poor steam from it.we drove the next day about 100 miles and the car overheated - steam billowing out of the hood. The bleeder screw was a bit mangled and steam was pouring out.
you can just replace the plastic bleeder screw. you can even buy some made if brass. less prone to heat brittling. but you don’t know yet if the top hose was cross treaded. so perhaps a new top hose is warranted.
good chance you’re fine