I was under the car a few weeks ago replacing the Constant Pressure Valve and while wiping up all the oil and grime noticed a notch worn into the rubber part of my expansion hose.
(Thanks to the forumites for belaying my fears that I had a head gasket leak and the fine tips on things like "drag link sockets" to replace the CPV).
Whatever Bubba tightened the 14 mm end didn't hold the line, so it rotated until the rubber hose hit the bottom of the block. It wore/melted almost all the way through.
Bought a new line, and before installing it I remembered that I had some 5/8" "Fire Sleeve" left over from doing the oil lines on my MR2. It was a perfect fit.
I know, it's overkill, but anything worth doing is worth overdoing.
Next time you're under there, I would recommend to everyone to check and make sure the line is clear of the bottom of the engine.