I was driving down the road today and noticed at the stop light my pedal started going down to the floor slowly. (1991 DX hatch)

Now my question is how would i be able to tell if it's the booster or Brake Master Cylinder??

O yea and when i poped my hood to inspect the problem i noticed there was like brake fluid on the big round black thing where the b.m.c. bolts to ,looked like there was a seal leak where b.m.c bolts to the black thing??

I dont have any brake mods or brake swaps.

 

First bleed your brakes real good and see if that helps.
Check for leaks also.

I used to have the same problem. Got a new BMC and everything was fine.

 

I had the same problem on my Dx, and it was the MC that was bad. After I replaced that it was good to go.

 

Bleed your breaks first if the problem still occcurs then its most likely your m/c

 

just get a master cylinder and bleed the brakes at the same time, no need in bleeding them twice
a lot of times when you bleed the brake system with the old master cylinder still on there it ends up getting clogged anyway
have fun