I have a 2007 King Ranch F150. It currently has 86K miles. 5.4L V8. I just flushed the original OEM coolant out and it was really, really brown/copper colored. (It was actually about the same color as my truck to give you an idea if you're familiar with the King Ranch Copper color)

Also, the tank has a sludge residue in it - the sludge was the same color as the coolant. I don't seem to burn any oil or transmission fluid, and I didn't see any rust particles/chunks to lead me to believe it was rust. Is this normal? I replaced it with the factory recommended Motorcraft Premium Gold stuff..and distilled water mixed per the manual.

Any thoughts or experiences of seeing the same is appreciated.

 

Are you the original owner?

 

flush the coolant out every 3 months until it stays clean again

 

Original owner = yes.

 

Doesn't sound right. The Long life (or extra long life ?) coolant is supposed to last longer than that. Even the standard coolant they used to use should have done better than that is the 3 years the truck has run since birth.

 

It is possible that the engine block had excessive core sand left in the cooling passages after the casting process. I'm just guessing here. The cast iron blocks use a casting core or mold composed of casting sand in a resin medium. The resin holds the sand together in its shape. When the casting cools the block goes through a shaker and a washer to breakup and remove the remaining core sand. Sometimes this process for whatever reason dosen't work like it should. You could take some of the sludge you found in the degas bottle and have an analysis performed to determine its origin. If you have not had any overheat issues then I doubt any problems will arise at this point. Again I'm just guessing on what this might be, it could be other things like rust as well. Like others have said you may want to flush it out a few times to insure its all gone. Take care.