Just wondered if anyone has any suggestions here. I plugged the hole today with a screw and the radiator blew when the car was hot. I'm not sure they're related (this is only the 3rd or 4th time I've driven it since I put in the new radiator, and the first time I really "pushed" it). But I do want to know what that hole is, if it's supposed to be there, and whether or not I should plug it.
Can someone else w/ a 540 just have a look at their expansion tank? Like I said, it's centered, in the dip between the filler cap and the coolant level sensor.
Thanks guys!