master cylender

Of course brake fluid will spray out if that bladder seal is torn. How did that happen? If that seal is blown up and mushy, the fluid is contaminated with a petroleum product. That is a very serious and expensive problem. If the seal is not deformed, just grab a cap with a good seal from a salvage yard.

The brake fluid should be replaced too because it absorbs moisture from the humidity in the air. That promotes corrosion and it lowers the boiling point from well over 400 degrees to 212 degrees. That leads to one form of brake fade when they get hot from normal driving. All you have to do is open the four bleeder screws and let them gravity-bleed for a few minutes with the reservoir cap loose so no vacuum will build up that will impede fluid flow. Keep an eye on the reservoir so it never runs empty. If it does it will take that much more work to bleed the system some more.