1996 Buick Skylark Owner's Manual - Page 210

How to Add Coolant to the Coolant Surge Tank If you haven't found a problem yet, the coolant level but isn't atthe FULL COLD mark, add 50/50 mixture of a clean water (preferably distilled) and DEX-COOL antifreeze at the coolant surge tank, but be sure the cooling system, including the coolant surge tank pressure cap, is cool before you do it. (See "Engine Coolant" inthe Index for more information.) I A CAUTION: -- Steam and scalding liquids froma hot cooling system can blow out and burn badly. They are you under pressure, and if you turn thecoolant surge tank pressure cap even a little they can ,come out at high speed. Neverturn the cap when the cooling system,,including the coolant surge tank pressure cap, is hot. Wait for the cooling system and coolant surge tank pressure cap cool if you to ever have to turn the pressure cap. - 5-17