Slight Grinding or Rubbing from Brake System

[Desert Rider]

I have a 1976 bronco with, I assume, stock brakes. When I apply the brakes by pressing on the brake pedal, there is a noticeable grinding or rubbing felt (and heard) while the pedal returns to its original position. This grinding/rubbing seems to originate from outside the cab, between the master cylinder and firewall. The are several moving parts, but I am thinking that this problem is located closer to the MC. I applied tephlon lubricant to all the moving parts, with no success.

 

[spap]

A grinding on front disk brakes kinda seem like the pads are gone and metal to metal on the rotor. Look at your rotors front side and back side to see any evidence of the pad being done.

 

[Desert Rider]

It is not coming from the actual brakes, it is originating from the brake pedal/linkage...between MC and firewall.

 

[Slowleak]

Power brakes?

 

[Rustytruck]

Check that everything is bolted tight. Bronco firewalls are known to crack. I would get someone under the hood while stopped and check for noise while braking hard with engine running and not while running. I have an aftermarket booster bracket that the brake push rod gets very close to rubbing the hole through the firewall. I would also check the bracket that is welded to the inner fender well and the firewall. make sure it isn't broken there. I would also check that you don't have rusted out inner fender liner where it attaches to the firewall assembly. On a good Bronco you can see the firewall move when you push the brake hard enough.
The whole brake/clutch pedal assembly is bolt in any thing loose there can cause a creaking groan noise.