loud squeal then pedal dropped

[popsthebuilder]

I've heard a loud squeal when I apply the brake for a few days. Also notices brake fluid run-off under master cyl/ booster area. Leaking from the reservoir closest to the fire wall.  Is this most likely a failure of the master cylinder, booster, or could it be something to do with the drum. Never worked on drum brakes before.   

[popsthebuilder]

73 c20

[79gmc15]

The master cylinder seals do eventually fail and leak at that point and needs replacement. Sounds like a good time to do a full brake inspection, your front pads can make a squealing noise.

[popsthebuilder]

Front pads still have plenty over a 1/4"

[bake74]

  Also notices brake fluid run-off under master cyl/ booster area. Leaking from the reservoir closest to the fire wall. 

     The seals in the master cylinder can fail.  If you are sure that is where it is leaking, then I would say the master cylinder either needs rebuilt or replaced.

[Jason S]

I've heard a loud squeal when I apply the brake for a few days.

  A few days is a long time keep the brakes applied... 
Seriously, it could be a scraper on the pads that is there to make the squeal to let you the pads are getting thin.

Also notices brake fluid run-off under master cyl/ booster area. Leaking from the reservoir closest to the fire wall.  Is this most likely a failure of the master cylinder, booster, or could it be something to do with the drum.

I agree with 79gmc15 and bake74, you need to rebuild or replace the master cylinder.  If one of the rear wheel cylinders had started leaking, you might see some evidence of brake fluid on the drums or backing plates.  Overall, if you are unsure about any of the brake system you might take the time and completely inspect and/or refurbish the system to be sure all is working like it should.

[popsthebuilder]

thanks