Things You Will Need
Replacement coolant, Adjustable pliers, Hose clamp pliers, Large container for catching the coolant, Garden hose, A new thermostat gasket for the six-cylinder, 5.2L and 5.9L engines, Gasket scraper, Lacquer thinner or acetone, RTV sealant, On 4.7L V8 engines a new O-ring,
Make sure the engine is cool before draining. Place a large container under the radiator drain to catch the coolant. If possible, attach a 3/8 inch diameter hosed to the drain fitting to direct the coolant into the container. Open the drain fitting and then remove the radiator cap. It may be necessary to use pliers to turn the drain fitting.
Drain the cooling system. While the system is draining, check the radiator and heater hoses as well as the clamps for wear or corrosion and replace if necessary. Remove the coolant reservoir and empty into the catch container.
After the system has drained, remove the thermostat and replace the thermostat housing without the thermostat. (See reference below for an article on removing and replacing the thermostat) The upper hose on the six-cylinder, 5.2L and 5.9L engines leads from the radiator to the thermostat housing. On the 4.8L V8 the lower hose leads to the housing.
Tighten the radiator drain plug and remove the upper radiator hose from the radiator. This is done by squeezing the tabs on the hose clamp and moving it back several inches on the hose away from the radiator. (If the clamps are the screw strap type, loosen the screw/bolt and slide back on the hose in the same manner.) Twist and remove the hose from the radiator. If the hose is stuck, use a pair of adjustable pliers near the end and twist the hose to break the seal. If the hose has deteriorated, cut it off and replace it.
Turn the heater controls on high to allow the heater core to be flushed at the same time. Place a garden hose in the upper radiator inlet where you removed the hose in step four above. Flush the system until the water runs clear at the upper radiator hose. Open the radiator drain and allow the system to drain again.
Install the thermostat and reconnect the radiator hose. Fill the radiator with the recommended fluid mixture of antifreeze and water until it reaches the bottom of the filler neck. Fill the reservoir to the full mark. Wait approximately five minutes and add more fluid if necessary. Coolant can be purchased in a premixed or concentrated liquid.
Replace the radiator cap but leave the reservoir cap open. Run the engine until the thermostat opens up. The coolant will begin to flow through the radiator and the upper radiator hose will become hot. Turn the engine off and allow it to cool. Add additional coolant to the reservoir if necessary to bring it back to the full mark. Replace the reservoir cap and then start the engine and allow it to reach normal operating temperature. Inspect the system for leaks. If any are detected, allow the engine to cool and tighten the hose clamps, thermostat housing bolts or replace the gasket and sealant or the rubber O-ring as necessary.
As an alternative to the above procedure, there is a flush kit available that provides a fitting that is placed in one of the heater hoses to facilitate flushing. This requires splicing the fitting into the hose. If you prefer to use this method, follow the installation instructions that come with the kit. The draining and refilling instructions as well as the thermostat removal requirements remain the same as above.
Timely flushing of your radiator can save money and help prevent the frustration of being stranded on the side of the road with a car that has overheated due to a clogged radiator or cooling system.
Tips & Warnings
Special hose clamp pliers are available at most auto parts stores.
Always allow the engine to cool before removing the radiator cap, draining the coolant or replacing the thermostat. Steam and hot engine coolant may be under pressure and their sudden release could result is serious burns.
Antifreeze is toxic. Do not leave in open containers or in puddles on the ground as children and pets may drink it.