1998 Buick Century Owner's Manual - Page 244

XI 6. Then fill the coolant recovery tank to the COLD mark on the overflow hose in the coolant bottle. 7. Put the cap back on the coolant recovery tank, but leave the pressure cap off. 8. Start the engine and let it run until you can feel the upper radiator hose getting hot. Watch out for the engine cooling fans. 9. By this time, the coolant level inside the radiator filler neck may be lower. If the level is lower, add more of the proper DEX-COOL" coolant mixture through the filler neck until the level reaches the base of the filler neck. 5-24