1996 Ford Mustang Owner's Manual - Page 251

Engine Coolant Drain and Flush Proper procedures for a complete coolant drain and flush of the cooling system can be found in the Car Service Manual. Following these recommended procedures will ensure that the specified coolant level and a 50/50 or appropriate mixture of coolant and water is maintained. Engine Coolant Refill Procedure When the entire cooling system is drained and refilled, the following procedure should be used to ensure a complete fill: NOTE: It is imperative the following procedure be adhered to. Failure to do so could result in damage to your engine. 3.8L engine only u Open the vent plug. u Remove coolant recovery reservoir cap. u Remove radiator pressure cap. u With the engine off and cool, add a 50/50 mixture of recommended cooling system fluid and water to the radiator until full, then add to the reservoir until the reservoir is at the FULL-HOT level. u Close the vent plug. u Reinstall the coolant recovery reservoir cap by installing the cap to the fully installed position. u Reinstall the pressure cap to the pressure relief position by installing the cap to the fully installed position, and then backing off to the first stop. 257