Ford Super Duty
5.4L Coolant Flush & Thermostat Replacement
2004 F250 4x4 XLT Sport Crew Cab
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At close to 100k miles, I figured it was time for a coolant flush and thermostat replacement.
Here's everything I used for the flush. Two jugs of Prestone Super Flush, four gallons of antifreeze, and 11 gallons of distilled water.
The first thing I did was remove the thermostat. I intended to replace it anyway, and removing the thermostat makes the flush job go quicker.
Use a large pair of pliers to release and pull back the hose clamp, and disconnect the hose.
Remove the two bolts holding the thermostat housing in place
Remove the o-ring
Remove the thermostat and re-install the thermostat housing, without the o-ring
Now, with the engine off and cool, remove the radiator cap and drain the coolant using the draincock
Then tighten the draincock and refill the reservoir with distilled water. It took about three gallons on mine. Run the engine for about 15 minutes with the cab heater turned on high.
Turn off the engine and allow it to cool, then drain the coolant again.
Then refill the reservoir with distilled water again, run the engine for another 15 minutes.
Repeat the drain-refill-run-drain step one more time.
Before refilling the system with antifreeze, I installed the new thermostat and o-ring.
After re-installing the thermostat housing, the hose, and the hose clamp, I refilled the reservoir with a little over three gallons of antifreeze.
I kept an eye on the coolant level after the first few trips and topped it off as needed to keep it in the normal range when cold.
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