FORD 2003 F-150 v.1 - Manual (Page 230)

For vehicles with overflow coolant systems with a non-pressurized cap
on the coolant recovery system, add coolant to the coolant recovery
reservoir when the engine is cool. Add the proper mixture of coolant and
water to the “cold full” level. For all other vehicles, which have a coolant
degas system with a pressurized cap, or if it is necessary to remove the
coolant pressure relief cap on the radiator of a vehicle with an overflow
system, follow these steps to add engine coolant.
To reduce the risk of personal injury, make sure the engine is
cool before unscrewing the coolant pressure relief cap. The
cooling system is under pressure; steam and hot liquid can come out
forcefully when the cap is loosened slightly.
1. Before you begin, turn the engine off and let it cool.
2. When the engine is cool, wrap a thick cloth around the coolant
pressure relief cap on the coolant reservoir (an opaque plastic bottle).
Slowly turn cap counterclockwise (left) until pressure begins to release.
3. Step back while the pressure releases.
4. When you are sure that all the pressure has been released, use the
cloth to turn it counterclockwise and remove the cap.
5. Fill the coolant reservoir slowly with the proper coolant mixture (see
above), to within the “cold fill range” or the “cold full” level on the
reservoir. If you removed the radiator cap in an overflow system, fill the
radiator until the coolant is visible and radiator is almost full.
6. Replace the cap. Turn until tightly installed. (Cap must be tightly
installed to prevent coolant loss.)
After any coolant has been added, check the coolant concentration, refer
to Checking Engine Coolant section. If the concentration is not 50/50
(protection to –34° F/–36° C), drain some coolant and adjust the
concentration. It may take several drains and additions to obtain a 50/50
coolant concentration.
Whenever coolant has been added, the coolant level in the coolant
reservoir should be checked the next few times you drive the vehicle. If
necessary, add enough 50/50 concentration of engine coolant and
distilled water to bring the liquid level to the proper level.
If you have to add more than 1.0 liter (1.0 quart) of engine coolant per
month, have your dealer check the engine cooling system. Your cooling
system may have a leak. Operating an engine with a low level of coolant
can result in engine overheating and possible engine damage.
Maintenance and Specifications
230