Brake Leak

My brakes are leaking on my 85' s-10, its coming somewhere from right under where you refill the brake fluid...what should I look to replace or do first?

It's an easy place to look really closely and find out where it's really coming from

It could be as simple as a loose fitting.

Since I know a little bit about my 85's I can make an educated guess, that it's the proporting valve. It's the little (gold if I remember correctly) device there with the lines all going to it.
You'll be lucky to find 1 in the dealer.

Look before you just start changing parts.

sounds more like a master cylinder. if the fluid is running down the booster and looks like its coming from the booster to where the master cylinder bolts up to it then thats what it is. it might be coming from the resivoir, around where it connects to teh master cylinder or it could be cracked. let us know a little more about where its coming from.

The reason why I say the proporting valve is because they are bolted right to the master cylinder, and they seem to be the weak link