- Draining the cooling system is always done with the engine COLD .
- Remove the reservoir tank cap.
- Remove the engine under covers.
- Position the drain pan under the draincock on the bottom of the radiator. Loosen the radiator and engine drain cocks. These should be opened to aid in draining the cooling system completely. If for some reason the radiator draincock can't be used, you can loosen and remove the lower radiator hose at its joint to the radiator.
- When the system stops draining, close both drain cocks as necessary.
- Using a funnel if necessary, fill the reservoir tank with a 50/50 solution of antifreeze and water. Allow time for the fluid to run through the hoses and into the engine.
- Start the engine and let it idle about 10 minuets; add the coolant/water mixture up to the FULL level.
- Install and secure the engine under covers.
- Securely tighten the cap.
- Race the engine 2000-3000 rpms for about 5 minutes, then stop the engine.
- After the coolant drops, remove the cap and add coolant to the FULL level again.
Proceed with draining the system as outlined above. When the system has drained, reconnect any hoses close to the radiator draincock. Move the temperature control for the heater to its hottest position; this allows the heater core to be flushed as well. Using a garden hose or bucket, fill the reservoir and allow the water to run out the engine drain cock. Continue until the water runs clear. Be sure to clean the expansion tank as well.
If the system is badly contaminated with rust or scale, you can use a commercial flushing solution to clean it out. Follow the manufacturer's instructions. Some causes of rust are air in the system, failure to change the coolant regularly, use of excessively hard or soft water, and/or failure to use the correct mix of antifreeze and water.
After the system has been flushed, continue with the refill procedures outlined above. Check the condition of the radiator cap and its gasket, replacing the radiator cap as necessary.