Hot June day in Texas on I-45 between Houston and Dallas. Cruising with the traffic flow when a tremendous crunching and metal rending noise emaninated from the dog house. We pulled over on the side of the road and after cooling off crawled under to assess the damage. DW said it sounded like the fan blade came off. (What do they know) Yep it was the fan blade. 1/2 of one blade had broken clean off and had traveled down to the balancer where it was stuck and making the horrible noise. I pulled it out and found no other damage so we slowly made it to the next town and a repair station. The break was a cvlean one with no cracks etc. We did not hit anything or have anything bounce up off the raod. We had checked this item when we checked the belt tension before we left. We had made no adjustments so it was a big mystery why the blade would fail as it did.