Properly change your own antifreeze/coolant to save on labor and avoid the purchase of a new radiator or engine. Buick's 3800 Series II engine is one of the best out there for power and dependability. However, any car can overheat due to poor cooling system maintenance. Inspect the hoses closely for cracks/leaks, the radiator for rust and the fluid for oil or grime. Drain and refill the cooling system every year or two to prevent corrosion of components like the head gasket, and to remove restrictive sediment buildup.
Drive the Buick up onto ramps in a garage or driveway, park and turn off engine. Apply emergency/parking brake and pop the hood. Place chalks behind both rear tires and wait for engine to cool.
Place bucket directly beneath lower radiator hose under car. Use channel locks to squeeze metal clamp release. Slide it further down hose, away from radiator. Pluck hose from radiator by pulling and twisting, taking care to aim hose into bucket. Open hood.
Apply downward pressure to radiator cap, twist a quarter turn and remove. Remove cap from overflow tank. Insert garden hose into radiator and blow out excess sediment with tap water (optional). Reconnect lower radiator hose and metal clamp after all liquid is finished draining.
Mix into jug a 50/50 solution of Dex-Cool to distilled water (70/30 if you live in a cold climate). Insert funnel into radiator and fill with mix until no more will fit. Mix more if needed. Clear engine area of equipment.
Start engine. Fill radiator with more coolant as level drops, taking care not to touch any other engine components. KEEPING CLEAR OF FAN, squeeze top radiator hose multiple times, removing any excess air bubbles from cooling system. Shut off engine after all air removed.
Replace radiator cap. Fill overflow reservoir to "MIN" line and replace cap. Start engine and allow to heat up to operating temperature. Rev engine gently to 3000rpm in 10 second bursts, PAYING CLOSE ATTENTION TO THE TEMPERATURE GAUGE. Allow engine to completely cool (may take a few hours).
Remove radiator cap, fill with more coolant mix, then replace cap. Fill overflow tank to "MIN." Close hood, remove chalks, release parking break, and back car off ramps. Store or dispose of used coolant per local law, and clean any spills. Load funnel and remaining coolant into Buick.
Drive until engine has been at operating temperature for 10 full minutes. Pull over, pop hood and carefully fill reserve tank to "MAX." Do not touch radiator cap. Once everything is at proper levels, it is safe to drive normally. Monitor temperature and coolant levels for the next few days in case any more trapped air escapes.
