What would cause brake master cylinder to almost be almost empty? on 1998 Chevrolet Lumina

98 Chevy Lumina V-6. I found the brake master Cylinder almost empty. Filled it up but have seen drops around the back firewall/middle of car some type of fluid recently. Just multiple drops. Some of it trans fluid I think. I don't see any wetness between the master and the booster. I haven't checked the wheel cylinders yet. Is there a brake line that goes from one front brake to the other somewhere between the firewall and engine? Is there any brake fluid blocks, ABS, etc. located around there? Please advise. Thank you.

Asked by for the 1998 Chevrolet Lumina
There are several places where fluid can leak. Fluid can actually leak out the back of the master cylinder and into the brake booster and you will never see anything externally. We would be more than happy to inspect the system for you if you would like.
1 more answer
Definitely a brake system leak. The complete system needs to be inspected: Master cylinder to the wheel cylinders. If you have ABS brakes the modulator could be the cause.