Firstly, I'd try to identify if the problem is the master cylinder.
Use vice grips to clamp off the flexible hose to the rear and both of the front flex hoses.
If you get no pedal it MUST be the master cylinder.
If you get a pedal, release the flex hose to the rear. If you still get a pedal, it must be the fronts.
Now you can selectively release the front hoses to narrow it down.
Use vice grips to clamp off the flexible hose to the rear and both of the front flex hoses.
If you get no pedal it MUST be the master cylinder.
If you get a pedal, release the flex hose to the rear. If you still get a pedal, it must be the fronts.
Now you can selectively release the front hoses to narrow it down.