My 95 F150 (5.8L EFI) started overheating. Even adding coolant it still overheated quickly. Naturally I thought it was the thermostat. I took of the hoses to get to the thermostat. The inside of every hose is colored with a rust-colored residue. Also, out of the coolant fill (where some of the coolant was bubbling out) is a dried up reddish residue.

The red colored stuff is either from some radiator stop leak that I put in about 5 years ago or iron that precipitated out of our tap water during and emergency water fill when it got hot. Not sure which one, but either way, it's there.

So... Any recommendations on how to get that junk out? I'm going to completely flush the coolant system and replace the thermostat. The hoses, externally, are in good shape.

Any suggestions?