Brakes mushy

[cmoore]

'70 F250 with a 360/C6 and brakes had been working fine.  It gets occasional use for home projects, nothing hard-core.  Jumped in the other day just to move it to the other side of the driveway and found the pedal went almost to the floor.  

Popped the master open and found the rear reservoir bone-dry, the front full.  Visually checked the rear and could not see any weeping.  Pads all around are fine but what am I missing as far as diagnosing hydraulically?  I'm a FNG at brake stuff and don't want to F it up.

Thanks for any help,

Chris

[ultraranger]

Not sure if your brakes are power or manual(?).

If manual, look at the back of the master cylinder to see if brake fluid has been leaking down the inside of the firewall.

If the brakes are power, You may be able to see brake fluid on the face of the booster or, the MC could be leaking into the booster which will destroy the diaphragm inside.