1994 Cadillac Fleetwood Owner's Manual - Page 240

_ How to Add Coolant to the Coolant Surge Tank If you haven'tfound a problem yet, but the coolant level isn't visible inside the surge tank add a 50/50 mixture of clean water (preferably distilled) and a properantifreeze at the coolant surge tank, but be sure the cooling system, including coolant surge tank pressure cap, is cool the before you do it. (See "Engine Coolant" in the Index for more information about the proper coolant mix.) 227