[buwalda]

Joe,
I have seen cases where an engine has sat for years & developed sediment in the cooling system. One engine I had was full of small, hard pieces of rusted block material, a little smaller than a grain of rice. No matter how many flushes I did, I could never completely get rid of this stuff. After only a few hours of driving, it would block many of the tube openings in the radiator & the engine would run hot. I then had to get the radiator rodded out. I ended up fitting a gauze filter in the top radiator hose to catch this stuff. I had to clean it out every couple of months & eventually I got rid of the stuff. I mention this because you said the radiator is 5-6 years old; it could be partially blocked.