Coolant Reserve Tank Cap

This small cap is a big safety part in your cooling system. It seals the coolant reserve (overflow) tank, keeping the system clean and helping maintain the correct pressure balance as coolant expands and returns during heat cycles. A good cap prevents leaks, reduces evaporation, and keeps air from entering the system ?.

Why this cap is needed

When the engine warms up, coolant expands and flows into the reserve tank. As the engine cools, coolant is drawn back into the radiator. The cap supports this process by sealing the tank and allowing the cooling system to work as designed.

How it works

The cap locks onto the tank neck and uses an internal gasket to make an airtight seal. This helps maintain proper coolant level behavior and keeps dust, moisture, and debris out of the coolant path ?.

What happens if it’s broken

• Coolant smell, stains, or wetness around the tank
• Coolant level drops faster than normal
• Air can enter the system, causing poor circulation
• Overheating risk increases, especially under load
• Dirty coolant and faster corrosion inside the system

Compatible Models

• Nissan Titan
• Nissan Armada