My 240 Wagon has an exhaust leak somewhere near the front of the car. It got really loud over the winter (which went unnoticed until someone pointed it out to me) and I could see white exhaust coming out from under the driver's door as well as when I opened the hood (only in the winter, now that it's warm I can't see it). I also get some exhaust smell inside, but nothing too bad (windows up or down).

Any ideas what it could be? A simple leak from a rusted exhaust system? Or is it a faulty Catalytic Converter? Are there ways that I can check without bringing it in?