Need Help Troubleshooting Brake Troubles

Signs of a bad booster are hard pedal. The primary indicator that the brake booster is going bad or failing is a brake pedal that is extremely difficult to push. ... if it’s not returning then I don’t think it’s booster.

Check here:

Is the spring in the MC? Where the push rod is?

Proportioning valve: take one line off at a time and apply the brake. If no fluid comes out that’s where the issue is.

Also: bad check valve for booster.

Lastly, spray some lithium grease or wd-40 on the pedal where it rotates as well. Maybe just needs some lube?