I just replaced the hose in 1 degree weather. I'm not sure if it made a difference. I did have to replace the stock clamp with a new hose clamp. I feel paranoid that i didnt fully seat the hose on the peg but im really anal and i psych myself out about a lot of stuff.
Also, i didn't read all 8 pages of this thread but the part number that was given on the page 2 isnt listed as a valid part number for the zetec engine past the year 2000 according to the ford parts guy. It lists the new hose covered in insulation as the correct part. I'll post the part number in a lil bit.