Important: If the engine is damaged internally and a new engine assembly is installed in the vehicle, make sure all foreign material is completely flushed out of the cooling system. The oil cooler system should also be flushed out, if equipped. Failure to rid the oil or cooling system of debris can result in damage to the replacement engine.

Important: Remove the thermostat before flushing the cooling system. Refer to Engine Coolant Thermostat Replacement .

You can use various methods and equipment to flush the cooling system. If special equipment is used, such as a back flusher, follow the manufacturer's instructions. However, always remove the thermostat before flushing the system.

In order to remove hardened scale from the radiator, a direct chemical action is necessary.

1. Add a flushing compound, at the specified rate of 30 grams-per-liter (4 ounces-per-gallon) of radiator capacity, to the coolant water as a dissolved solution while the engine is running.
2. Operate the engine for 15 minutes.
3. Drain the cooling system. Then, flush the system with clean drinkable water.

There are various types of flushing compounds commercially available. Obtain these from a reliable source.

Most compounds attack metals and these should not remain in the engine for more than a few minutes. Use a neutralizer in the cooling system immediately after using a de-scaling solvent. For extremely hard, stubborn coatings, such as lime scale, use a stronger solution. The corrosive action of a stronger solution affects the thin metals of the radiator, reducing the operating life of the radiator. Because of this, flushing and rinsing the radiator is required.

After you use the solvent and the neutralizer, and after you flush the system, do the following:

1. Drain the entire cooling system. Refer to Cooling System Draining and Filling .
2. Fill the system with clean drinkable water and a rust inhibitor or high boiling type antifreeze.
3. After filling the cooling system, check the radiator and hoses for coolant leaks.