Brake Fluid Reservoir Cap for Nissan – OEM-Grade Seal ️

This replacement cap keeps your hydraulic system clean, dry, and safe. It seals the master cylinder reservoir, controls venting, and protects brake fluid from dust and moisture. That matters because brake fluid is hygroscopic; when it absorbs water, its boiling point drops, pedal feel gets soft, and components corrode.

Why this part is needed

The cap maintains an airtight barrier with a molded rubber diaphragm and gasket. It stabilizes pressure during temperature changes and level swings, preventing aeration and fluid splash. Many versions include a level switch to warn you early if fluid is low.

How it works

A precision vent lets air in as pads wear while blocking contaminants out. The diaphragm collapses as fluid level falls, keeping ambient humidity away from the fluid surface. A clean seal equals consistent pedal and longer ABS/modulator life.

What happens if it’s broken ⚠️

Moisture intrusion, rusty internals, spongy pedal, longer stopping distance, warning light flicker, leaks around the neck, and possible ABS pump damage. In short: degraded braking and higher repair costs.

Tech tips

Inspect the gasket for hardening or cracks, clean the neck, use only DOT 3/4 as specified, and hand-tighten—no tools needed.

Compatibility

• M30