The 525i 1990 I just bought has a leaking bleeder screw on the radiator. I bought a new one with washer at the stealer, however it leaks also. I am loosing coolant after driving several miles. Anybody have any ideas? Should I go find a regular bolt and use it? Also I was told the radiator has a bolt for draining, however all I can find is a plastic blue bolt located at the bottom of the reserve tank attached to the radiator.