Hey, just did this. Mine is a 2003 F150 Off Road model with the 5.4L Triton. There are also sorts of articles and posts about how to do this and achieve the correct 50/50 mix etc., so I will just include the high lights (and low lights)

1: First off the block drain plugs? On this 5.4 engine, they are 8mm Hex/Allen bolts (Hex and Allen are the same thing). Not Torx, not 5/16, its an 8mm hex and requires an 8mm Hex bit. I easily got the drivers side out, and it drained another 1/2 gallon. I did not even try the passenger side as it seemed impossible to get to.

2: How much can you drain out by gravity? I consistently got 3 gallons out via the radiator and the drivers side block drain. The cooling system on my truck holds 24 Quarts or 6 Gallons. PS the hose size to extend and redirect the radiator drain is 1/2" inner diameter.

3: Did I use the the 22oz bottle of the Ford/Motorcraft cooling system flush? Yes. I followed the directions on the bottle and they tell you to put it with the old coolant and leave it in for 10 minutes. It takes longer than that to warm my Truck up, so I did more like 30 minutes.

4: After the initial drain of the coolant and chemical? I did three cycles of fill/Warm up/and drain. Adding and draining 3 gallons of distilled water each time. Did the final flush yield relatively clean water on the last drain?
Hell no, it was still dirty.

5: I felt confident that after 3 cycles of flush with distilled water, that all that was now in there was distilled water. I added three gallons of Prestone antifreeze. The truck calls for the Brown Ford antifreeze, but I had Prestone in there and that's what I use. I think its compatible with all normal vehicles.

6: I also replaced the upper and lower rad hoses and the thermostat and gasket. Those OEM Ford compression type hose clamps? They can be pesky to remove in tight spaces. The only one that gave me trouble was the lower rad hose on the engine end. Its really to tight to get channel locks etc in there. The trick? Use a normal screw type hose clamp (about a half dollar in size). Put it over the compression points on the Ford clamp and tighten it with a 1/4" ratchet and proper size socket. Works like a charm!! Removing the thermostat? Those two 10mm bolts holding the thermostat cover on? They are close to 4" long, so use at least a 3/8" drive ratchet and also be sure to clean the threads and apply anti-seize before re-assembly. Be care not to snap these when removing.

7: Throw those Ford OEM clamps in the trash and replace them with normal stainless steel screw/socket type normal hose clamps.

8: I also removed and cleaned out my De-gas bottle/Overflow tank and replaced the cap with a new one (I used Ford OEM for everything).

What would I do different next time? In my quest not to use tap water, I relied on the chemical cleaner and gravity flushing to clean the system. Next time I will bare minimum put a garden hose in the De-Gas bottle, leave the drain **** open and maybe even remove the lower radiator hose, and flush that puppy until it runs clear. Then I would go thru the process detailed above with distilled water to get out all the mineral rich tap water.
I realize that this process will not flush the water jacket, but I am not willing to install one of the "Flushing T" kits from Prestone. I think its just introducing a point of failure as they are just cheap plastic and more clamps etc.

Please feel free to respond and add any tips to make this process better.

Keep on Truckin
DWILD.

 

I personally think the cautions about tap water are overblown. Let's do some math. From this study, the mineral content of North American Tap water ranges from 2-83 mg/L of Ca and 0-29 mg/L of Mg. Let's take the WORST case possible and use the upper limits of those ranges, so assume your tap water has a total of 112 mg/L mineral content, which is approx 0.004 ounces per liter. That means a six gallon flush contains at most one hundredth of an ounce of minerals. That doesn't seem like very much. Certainly not enough to clog half inch passageways. And that assumes that 100% of those minerals precipitate inside the engine and affix themselves to the block. But that's the opposite of what happens. Mineral solubility in water increases with temperature. Since you are adding cold tap water and heating it up by running the engine, you are actually dissolving minerals from the block and flushing them out, not adding them. Maybe if you left that water in for years, over hundreds of heating/cooling cycles those minerals might deposit in the block, but that still doesn't seem like much when spread over the surface area of all the interior water passageways.

So my personal view is that your suggested procedure to flush with tap water and fill with distilled is fine. It is far more important that you regularly exchange fluids than to do it perfectly. As your coolant breaks down, it is unable to inhibit corrosion and the block starts to rust. All that rust is far more likely to clog passageways than a miniscule amount of mineral content.

 

You should reuse the factory clamps. They're designed to place even pressure all the way around the plastic fittings. Worm style clamps put uneven pressure on plastic and fit fine initially but repetitive engine heat cycles will allow the worm clamp to deform the plastic tubes creating future leaks.