Ford 2003 Mustang Workshop Manual page 1855

To maintain the integrity of the coolant and the cooling system:
Add Motorcraft Premium Gold Engine Coolant VC-7-A (in Oregon VC-7-B) or equivalent
meeting Ford specification WSS-M97B51-A1 (yellow color). Use the same coolant that
was drained from the cooling system. Do not mix coolant types.
Do not add/mix orange-colored Motorcraft Speciality Orange Engine Coolant VC-2 or
equivalent meeting Ford specification WSS-M97B44-D. Mixing coolants may degrade the
coolant's corrosion protection.
Do not add alcohol, methanol, or brine, or any engine coolants mixed with alcohol or
methanol antifreeze. These can cause engine damage from overheating or freezing.
Do not mix with recycled coolant unless it meets the requirements of Ford specification
WSS-M97B51-A1. Not all coolant recycling processes meet these Ford specifications.
Use of such coolants can harm the engine and cooling system components.
NOTE: The addition of Motorcraft Cooling System Stop Leak Pellets, VC-6, darkens Motorcraft
Premium Gold Engine Coolant from yellow to golden tan.
1. Place the heater temperature selector in the maximum cool position.
2. CAUTION: On 3.8L engines, the vent plug must be removed before radiator fill or
the engine may not fill completely.
NOTE: It is important to maintain engine coolant concentrate between 40 percent or -24°C (-11°
F) and 60 percent or -52°C (-62°F).
Fill the engine cooling system with 50/50 mixture of water and engine coolant.
3. After filling the engine cooling system, add coolant to the vent until full. Install the vent plug.
4. Leave the pressure relief cap off and run the engine until it reaches normal operating
temperature.
5. Stop the engine and add the correct engine coolant mixture to the degas bottle/coolant
expansion tank until the coolant level is between the COOLANT FILL LEVEL marks.
6. Turn the engine off and allow the cooling system to cool. Check the level in the degas
bottle/coolant expansion tank, and add a 50/50 mix as needed.
Filling — 4.6L (2V)