QUOTE(Hammy @ Apr 13 2006, 08:27 PM)
They're designed so that when the cable breaks they spring open.
The thump you hear when you let the bracket go is the passenger side flap closing down on the trailing edge of the oil cooler duct. This routes maximum airflow through the oil cooler when the engine has warmed up. Some air continues to pass over this flap to the passenger side cylinders and the same happens on the drivers side. This is the fail safe position. If you run the engine like this it will take a little longer to warm up the oil.
When the engine is cold the passenger side flap is lifted off the trailing edge of the oil cooler duct and most of the air flowing through the passenger side duct flows past the oil cooler to the cylinders. This lets the oil warm up faster.