So I accidentally loosened the brake caliper banjo bolt when replacing my brake pads and brake fluid leaked from it. How likely is it that I have introduced air into the brake line system?

 

Somewhat likely to have gotten air in the line.

 

Yeah, I would bleed it just to be sure. If you haven't done it before, it's no big deal...just search for some directions.

 

I'm no expert on brakes so excuse me if this is an obvious question. But would I only need to bleed the brake that I accidentally leaked fluid or would I have to bleed all 4 corners?

 

all you need to do is bleen the one caliper.......just find the right wrench size for the bleeder, and have someone pump the brake pedal a couple of times and hold it down, then you open the bleeder. but keep your finger slightly over the bleeder hole to feel the air come out. just do this a few time and i think that you will be alright. MAKE SURE THAT THE BLEEDER IS CLOSED BEFORE THE PERSON HOLDING THE BRAKE PEDAL DOWN RELEASES IT. if its released before it will suck in more air.

 

Or rather than feeling the air, I would find a clear piece of tubing that you can put over the bleed nipple. that way you can actually SEE the air bubbles. Once they stop for a few pumps you're probably good.