I have a 2000 expy with the 5.4 just turned over 200k. I bought the upper and lower radiator hoses awhile back and finally gotta chance to change them out. I noticed i got the wrong bottom hose so I only swapped out the top hose. I filled it back up with 1.5 gal of distilled water. After I drove it about 60 miles I checked the overflow tank and noticed copper colored flakes in it. Im assuming the previous owner put some stop leak in it but not sure Ive never had any problems as far as overheating or losing coolant. What else could it be? Im going to get the right bottom hose and do a flush. Can I use the bottom hose I have, its got the two extra hoses for the oil cooler? I was just going to connect the two hoses together but not sure if that will cause a problem.

 

I had a 2001 F150 5.4 that overheated and cracked the head gasket or head... I don't know. I used BARS LEAK COPPER in it and it lasted about 1 year... then I would flush and do it again..... I did that for 30 years and 50K miles and never had an overheating problem.. If you flush and refill, monitor the overflow tank to see if it starts slowly using coolant.