1995 GMC Yukon Owner's Manual - Page 250

The coolant level should be at or above the COLD mark.If it isn't, you may have a leak in the radiator hoses, heater hoses, radiator, water pump or somewhere elsein the cooling system. NOTICE: Engine damage from running your engine without coolant isn't covered by your warranty. If there seems to be no leak, start the engine again. See if the fan speed increases when idle speed is doubledby pushing the accelerator pedal down. If it doesn't,your vehicle needs service. Turn off the engine. How to Add Coolant to theCoolant Recovery Tank If you haven't found a problem but the coolant level isn'tat or above yet, the COLD mark, a 50/50 mixture of clean water (preferably distilled) add and a proper antifreeze at coolant recovery tank. (See "Engine Coolant" the in the Index formore information about the proper coolant mix.) 5-12