Coolant Flush How-to: 1991 GMC C2500 Sierra SLX 4.3L V6 Standard Cab Pickup

Learn how to flush the coolant (antifreeze) in your 1991 GMC C2500. Coolant / antifreeze circulates through C2500 radiator and engine to maintain the proper temperature. Coolant / antifreeze also passes through the heater core under your cowl to provide heat to the cabin of your C2500. In addition to preventing your car from overheating, coolant / antifreeze also helps lubricate the seals in the water pump and hoses. Start your coolant flush by draining the coolant / antifreeze that is in your reservoir, then drain the coolant that is in your radiator by opening the petcock or removing the lower radiator hose. This video shows where the radiator drain plug (petcock) is located on a 1991 GMC C2500. Fill up the radiator with distilled water and run the engine. Turn off the engine and drain the water, fill up the radiator with antifreeze until you have a 50/50 coolant / distilled water mixture and burp the system.