1993 BMW 525i

I dont recommend bypassing the heater core because it is a safety issue, no defrost. Repair may be a bit too involved for the layman, are you up to the task? Blocking all the lines going into the fire wall will stop the leak. Release the clamps and insert some sort of plug of the approximate size to fill the hose, I believe 19mm is the diameter of the inlet pipes.

When refilling, be sure to get all the air out of the system or it will over heat. Open the black plastic screw next to the radiator cap and fill the system until all the bubbles are gone, then close the screw, be careful, it is just plastic.