Flushing the Cooling System

FLUSHING THE COOLING SYSTEM
When the engine's cooling system becomes contaminated, it should be flushed thoroughly to remove the contaminants before the engine is seriously damaged. One source of contamination that is damaging to the engine if not corrected immediately is a cracked oil gallery. With a cracked oil gallery, oil will be forced into the cooling system while the engine is operating, and when it is stopped, coolant will leak into the lubricating system. If mixed with oil in the crankcase, this antifreeze forms a varnish, which quickly immobilizes moving engine parts.
To remove such contaminants from the engine, both the cooling system and the lubrication system must be thoroughly flushed after the engine is repaired.

CAUTION: DO NOT REMOVE CAP OR OPEN COOLING SYSTEM DRAINS FROM A HOT SYSTEM. ALLOW SYSTEM TO COOL FIRST.

If the engine has had a failure resulting in the contamination of the cooling system with lubricating oil, or a substance other than a recommended antifreeze has been added, the following procedure is recommended:

1. Drain coolant.
2. If L61, remove heater core inlet and outlet hoses from engine outlets.
3. If L81, remove heater core outlet hose from auxiliary coolant pump and rear inlet hose from front inlet hose.
4. Place end of heater core inlet hose (lower heater core pipe is inlet) in a container and apply low-pressure shop air 35 kPa (5 psi) to heater core outlet hose to blow coolant out of heater core.
5. Install heater inlet and outlet hoses.
6. Prepare a mixture of Calgon or equivalent (automatic dishwasher detergent), and water at the ratio of two ounces (dry measure) to 3.8 liters (1 gal.) of water.
7. Remove the engine thermostat to permit the Calgon (or equivalent) and water mixture to circulate through the engine and the radiator.
8. Fill the cooling system with the Calgon (or equivalent) solution.
9. Prepare a mixture of automatic dishwasher detergent and water at the ratio of two ounces (dry measure) to 3.8 Liters (1 gal.) of water.
10. Run the engine for 5 minutes.
11. Drain the cooling system.
12. Repeat Steps 8 through 11.
13. Let the engine run 5 minutes.
14. Drain the cooling system completely.
15. Install new engine thermostat.
16. Install new main water pump.
17. Use clean water to rinse away any coolant that was spilled during service.
18. Fill cooling system.