OK, I need some help with my '67 G.T.500.

Well you obviously have a leak. First run your hand under the brake master cylinder and feel for wetness. If its wet then the master cylinder is leaking. Sometimes they leak around the brake lines at the master. If it is dry they sometime leak at the back of the master cylinder and leak down the back onto the booster. If you dont see anything there,crawl under the car and look for drips. Brake lines can rust out and leak. If nothing in view then pull off the rear wheels and brake drums. Check the wheel cylinders for leaks. Strong possibility. I'm leaning towrds a Master Cylinder leak. Very common.
Hope this helps.
Jim

 

Hi to a 67 owner. First I would not drive,nor take any chances driving a car without good brakes.You should look for any type of fluid leaks with a flashlight.If you dont see anything the fluid loss could be from the master cylinder-into the booster.If the car pulls as you apply the brakes it could be a wheel cylinder or brake caliper leaking.Please be careful!! Many of the parts are available from various sources,so let us know what you need.And consider a safe way (car trailer-u haul or tiltbed) to transport you to the shop.It may also be repairable in your home garage.Give this some careful thought.Keep us posted
Regards P.D.

 

Also check the large vacuum hose that connects the booster and engine. Have seen a number of cars where the leaking master cylinder is leaking to the booster and the vacuum pulls the fluid into the engine through the vacuum hose. Check and see if it's "wet" inside and if so if its brake fluid

 

By the way, brake fluid will absolutely destroy any paint that it comes in contact with for any amount of time so be very careful.
Cheers,
Carl