The procedure I referred to is for when you drain all the coolant. Adding small amounts of coolant and letting it bubble up any small amounts of air is fine. The tool referred to in the procedure is just one of several that are available. Because of the pressurized reservoir, draining and refilling is different from what you may be used to in the past. The tool creates a vacuum in the cooling system and sucks in the replacement coolant with no air pockets. I always use the concentrate and distilled water to make my own 50-50 mixture. If I were replacing questionable coolant, I would drain the old stuff, fill it once with distilled water, then drain that. Then I would use a slightly more than 50% coolant mixture to make up for the inevitable pint of two of water that will not drain.
Here is the procedure from the FSM:
CAUTION:
Failure to purge air from the cooling system can result in an overheating condition and severe engine damage.
NOTE:
The preferred method to remove air from the cooling system is to use Tool, UView Airlift™ Cooling System Refill 399-550000 , or equivalent,.
Evacuating or purging air from the cooling system involves the use of a pressurized air operated vacuum generator. The vacuum created allows for a quick and complete coolant refilling while removing any airlocks present in the system components.
NOTE:
To avoid damage to the cooling system, ensure that no component would be susceptible to damage when a vacuum is drawn on the system.
WARNING:
ANTIFREEZE IS AN ETHYLENE GLYCOL BASE COOLANT AND IS HARMFUL IF SWALLOWED OR INHALED. IF SWALLOWED, DRINK TWO GLASSES OF WATER AND INDUCE VOMITING. IF INHALED, MOVE TO FRESH AIR AREA. SEEK MEDICAL ATTENTION IMMEDIATELY. DO NOT STORE IN OPEN OR UNMARKED CONTAINERS. WASH SKIN AND CLOTHING THOROUGHLY AFTER COMING IN CONTACT WITH ETHYLENE GLYCOL. KEEP OUT OF REACH OF CHILDREN. DISPOSE OF GLYCOL BASED COOLANT PROPERLY. CONTACT YOUR DEALER OR GOVERNMENT AGENCY FOR LOCATION OF COLLECTION CENTER IN YOUR AREA. DO NOT OPEN A COOLING SYSTEM WHEN THE ENGINE IS AT OPERATING TEMPERATURE OR HOT UNDER PRESSURE; PERSONAL INJURY CAN RESULT. AVOID RADIATOR COOLING FAN WHEN ENGINE COMPARTMENT RELATED SERVICE IS PERFORMED; PERSONAL INJURY CAN RESULT.
WARNING:
WEAR APPROPRIATE EYE AND HAND PROTECTION WHEN PERFORMING THIS PROCEDURE.
NOTE:
The service area where this procedure is performed should have a minimum shop air requirement of 80 PSI (5.5 bar) and should be equipped with an air dryer system.
NOTE:
For best results, the radiator should be empty. The vehicle's heater control should be set to the heat position (ignition may need to be turned to the on position but do not start the engine).
1.Refer to the service equipment tool's operating manual for specific assembly steps.
2.Choose an appropriate adapter cone that will fit the vehicle's cooling system filler neck.
3.Attach the adapter cone (2) to the vacuum gauge (1).
4.Make sure the vacuum generator/venturi ball valve (3) is closed and attach an airline hose (2) (minimum shop air requirement of 80 PSI/5.5 bar) to the vacuum generator/venturi (1).
5. Position the adapter cone/vacuum gauge assembly into the filler neck. Ensure that the adapter cone is sealed properly.
6.Connect the vacuum generator/venturi (2) to the positioned adapter cone/vacuum gauge assembly (1).
7.Open the vacuum generator/venturi ball valve.
NOTE:
Do not bump or move the assembly as it may result in loss of vacuum.
8.Let the system run until the vacuum gauge shows a good vacuum through the cooling system. Refer to the tool's operating manual for appropriate pressure readings.
NOTE:
If a strong vacuum is being created in the system, it is normal to see the radiator hoses collapse.
9.Close the vacuum generator/venturi ball valve.
10.Disconnect the vacuum generator/venturi and airline (1) from the adapter cone/vacuum gauge assembly (2).
11.Wait approximately 20 seconds, if the pressure readings do not move, the system has no leaks. If the pressure readings move, a leak could be present in the system. Check for leaks and repeat the procedure.
12.Place the tool's suction hose into the coolant's container.
NOTE:
Ensure there is a sufficient amount of coolant, mixed to the required strength/protection level available for use. For best results and to assist the refilling procedure, place the coolant container at the same height as the filler neck. Always draw more coolant than required. If the coolant level is too low, it will pull air into the cooling system which could result in airlocks within the system.
13.Connect the tool's suction hose (1) to the adapter cone/vacuum gauge assembly (2).
NOTE: View typical
14.Open the suction hose's ball valve to begin filling the cooling system.
15.When the vacuum gauge reads zero, the system is filled.
NOTE:
If filling through a pressurized coolant bottle, stop filling when the proper level is reached.
16.Close the suction hose's ball valve and remove the suction hose from the adapter cone/vacuum gauge assembly.
17.Remove the adaptor cone/vacuum gauge assembly from the filler neck.
18.Install the cap on the filler neck.
19.Start and run the engine
with the heater control unit in the HEAT position.
20.After the engine has reached normal operating temperature, shut the engine off and allow it to cool. When the engine is cooling down, coolant will be drawn into the radiator.
21.Add coolant to the pressurized coolant bottle or reservoir tank as necessary. Only add coolant to the container when the engine is cold. Coolant level in a warm engine will be higher due to thermal expansion. Add necessary coolant to raise container level to the COLD MINIMUM mark after each cool down period.
22.Once the appropriate coolant level is achieved, install the cap on the filler neck.