I think the cap to my brake fluid is leaking. Does anyone know if I need to get an entire new cap or do I just need to replace the rubber ring underneath the cap?

Thanks,
-A

 

I don't think that your brake fluid should even get near the cap if it is filled properly. I think that the cap is there to prevent dirt and moisture from entering the system.

Try to clean up the brake fluid and try to locate the source of the leak by having someone push the brake pedal.

 

What leads you to think it's the cap leaking?
If there is fluid on the face of the booster Under the master cylinder, the master needs replaced .