x2 my car had this issue. check the brake booster or the master cylinder if its leaking.It's not the master cylinder leaking from the firewall?
The tray,so to speak? like the area where your excess water is supposed to drain to the road in front of your windshield,if so,would that cause it to the location of the heater core and to the top of the pedal area?i had that problem . it turned out to be the "cowl" the part where the windshield wipers are.
water gets in because of the weather stripping corrodes away. i was getting water in the passanger side to because water would get in through the heater core.