Parts for your 2020 Nissan Serena-Radiator cap

2020 Nissan Serena radiator cap — what it does and how to look after it

Based on Nissan’s technical documentation, the 2020 Nissan Serena (C27 series, MR20DD S-HYBRID) is fitted with a conventional radiator pressure cap. The Nissan Serena C27 Service Manual (Cooling System – CO section) specifies inspection and pressure-testing of the radiator cap, and the Nissan electronic parts catalogue (FAST) lists a radiator cap (0.9 bar class) for C27 models. Major aftermarket catalogues for AU/NZ applications also show a 0.9 bar cap option for the 2016–2022 Serena range. That makes the radiator cap relevant for routine servicing on a 2020 Serena.

The radiator cap’s job is simple but crucial. It seals the cooling system and holds a set pressure so the coolant’s boiling point is raised, keeping the Serena running cool under load or in summer heat. Inside the cap is a spring-loaded pressure valve and a smaller vacuum valve. When the coolant heats up and expands, the cap lets excess coolant flow to the reservoir. As the engine cools, the cap draws coolant back in so there’s no air left in the system. A healthy cap helps prevent overheating, hose collapse, and coolant loss.

When servicing a 2020 Serena, it’s worth giving the cap a once-over. Never open it hot—wait until the engine is cold, use a cloth, and open to the first detent to release any residual pressure. Check for:

• Hardened, cracked, or swollen rubber seals
• Corrosion on the seat or cap body
• Weak spring tension or stuck valves

A cooling system pressure tester with a cap adaptor can confirm the opening pressure (the Serena commonly uses around 0.9 bar/88 kPa—always match the vehicle label or service data). If the cap won’t hold the specified pressure, replace it.

Practical tips for owners and workshops:

1. Use the correct pressure rating cap, too low can cause boil-over, too high can stress hoses and the radiator.
2. If you’ve had overheating, hose collapse, random coolant loss, a sweet smell, or the reservoir overfilling/emptying erratically, suspect the cap early.
3. When topping up, use the correct Nissan long-life coolant (blue) premix or a compatible silicate-free coolant, and bleed air as per the service manual.
4. As preventative care, consider replacing the cap at major coolant service intervals (for many owners, about 5 years or 100,000 km), or sooner if any doubt.

A quality, correctly rated cap is inexpensive insurance for the Serena’s cooling system and hybrid drivetrain reliability.

Popular questions

What pressure radiator cap does the 2020 Nissan Serena use?
The C27 Serena typically uses a 0.9 bar (approx. 88 kPa) cap. Variations can exist by market and radiator supplier, so always check the under-bonnet label, the existing cap’s markings, or the Nissan service data before purchasing.

How often should the radiator cap be replaced on a 2020 Serena?
There’s no hard expiry, but replacing the cap at major coolant service intervals—around 5 years or 100,000 km—is sensible. Replace immediately if it fails a pressure test, the seals are perished, or there are cooling system symptoms linked to cap performance.

Is it safe to open the radiator cap when the engine’s hot?
No. Opening a hot cap can release scalding coolant and steam. Wait until the engine is completely cool, use a rag, and open to the first detent to bleed any residual pressure before removal.