My wife's '01 330Ci has a slight coolant leak from somewhere under the intake manifold. I cannot find it, so I want to pressurize the cooling system to see if I can hear or see where it is coming from. I need a new radiator cap anyway, so I thought I would drill a hole in the existing one and mount a metal schrader valve to pressurize the system with my air compressor. If the Thermostat is closed, will this block me from pressurizing the system from the expansion tank?
