smadayrrep

I have a 1998 F150 and while hauling about a half ton of bricks I smelt burning brake fluid after going down some relatively steep hills. I saw a little fluid running down the front driver's side rim. No fluid was around the engine block. I refilled the brake fluid and took it to the shop a few days later but they can't find anything wrong. Any ideas of how to identify the source of the leak?