Lincoln/Mercury Repair: Mercury Villager strange sounds, mercury villager, pre purchase inspection


Question
I have a '94 Mercury Villager that's making a faint sporatic hissing sound from the front passenger side.  It's sort of like a very faint scraping sound.  It only happens when the vehicle is cold.  It seems to be related to the brakes.  When stopped, the sound isn't there.  The sound appears around 10-15 mph.  It disappears when the brake is pressed.  The sound goes away eventually as the vehicle warms up.

I just purchased this car, and my one test drive was with the vehicle warm, but I did pay for a pre-purchase inspection.  The mechanic who looked at the van did not say that there was anything wrong with the brakes, though he did say that the pads are at about 20-30%.

Any ideas?

Answer
it is common of some quality of rotors or pads to rust overnight. it takes some brake applications to clean them up again. this is fairly normal. since the brakes are 20% remaining i would replace them anyway before winter. any brake problem should be inspected in a shop. brakes are too important to forget about.