1999 5.4 4x4
Replaced my heater core and drained out around 2.5 gallons. Reservoir level on the max mark beforehand. Checked the owner's manual and it specs 27.9 quarts as capacity. Surely this must be a typo......right? Otherwise, I have to add back almost 7 gallons of coolant. I left the radiator petcock open all night and there was nothing, not even a drop, draining out the next morning. 2.5 gallons out was all there was. The engine never runs hot and I do tow with this rig. So what gives, where is the other 4.5 gallons hiding if it really does take 27.9 qts.?

 

No it's not a typo. That figure includes not just the radiator, but also the coolant chambers within the engine, all of the hoses, the overfill bottle, and the rear heating system as well. When you refill, remember that you don't use all coolant, you use a 50/50 mix of coolant and water.