1998 Buick Skylark Owner's Manual - Page 205

How to Add Coolant to the Coolant Surge Tank If you haven't found a problem yet, but coolant level the isn't atthe FULL COLD mark, add a50/50 mixture of clean water (preferably distilled) and DEX-COOL@ coolant at the coolant surge tank, but be sure the cooling system, including the coolant surge tank pressure cap, in is cool before youdo it. (See "Engine Coolant" the Index for more information.) Steam and scalding liquids from cooling a hot system canblow out and burn you badly. They are underpressure, and if you turn thecoolant surge tank pressure cap even a little they can come out at high speed. Never turn the cap when the cooling system, including the coolant surge tank pressure cap, hot. Wait for is the cooling system and coolant surgetank pressure cap to cool if you ever have to turn the pressurecap. -- -- Adding only plain water to your cooling system can be dangerous. Plain water, or some other liquid likealcohol, can boil before the proper coolant mixturewill. Your vehicle's coolant warning system set for the proper coolant is mixture. With plain water thewrong mixture, or CAUTION: (Continued) 5-18