2007 Cadillac XLR-V Owner's Manual - Page 395

1. You can remove the coolant surge tank pressure cap when the cooling system, including the coolant surge tank pressure cap and upper radiator hose, is no longer hot. Turn the pressure cap slowly counterclockwise. If you hear a hiss, wait for that to stop. A hiss means there is still some pressure left. 2. Then keep turning the cap and remove it. 3. Fill the coolant surge tank with the proper mixture until the level inside the surge tank stabilizes at the FULL COLD mark on the front of the surge tank. 395