I have a 06 5.4 and I was going to do a coolant flush....I was gonna flush with a flush additive and just use the garden hose but I was wondering after I'm done flushing the system how many gallons of concentrate should I add before I start to add the mixed concentrate?

 

these are my notes for my 4.6, but believe it’s same for yours: 20qt system, ~ 10 drainable and ~ 10 block.

find fordtechmakeuloco on youtube and follow his diy flush video.

if your system hasn’t been maintained well in the past, you should plan on needing to do several rounds of flushing before being done.

 

After flushing with garden hose, I would fill and drain with distilled (warm up to get thermostat to open then let cool and repeat)
Your system is now 100% water and full drain will only remove about 10 quarts so 10 quarts fresh remains + 10 quarts of 100% concentrated antifreeze added = 20 quarts of 50/50 antifreeze in your system. Make sure you buy concentrate, 100% antifreeze.
Antifreeze testers are cheap.

 

thank you I appreciate it