I have a leak in one of my steel front brake lines. How can I stop the flow of brake fluid?
You can’t. The warning light only indicates a pressure difference in the system. It does not disable the brakes. Don’t mess with brakes. A car with leaking brakes is unsafe and should not be driven. Get it towed to the garage or talk the people in the garage and see if they can help you push it with someone inside to activate the parking brake.
There are two reservoirs in the master cylinder. You wont totally run out of fluid. You should still have brakes on the back. No you can’t manually engage the pistons. Just go slow and use the transmission to slow down (down shift) you can use the parking brake to stop then release the brake to go.