Parts for your 2001 Nissan Primera-Radiator cap

Radiator cap for the 2001 Nissan Primera

Based on technical references including the Nissan Primera P11/P12 Factory Service Manual (Cooling System section) and Nissan FAST electronic parts catalogue for P11.144 and early P12 chassis, the 2001 Nissan Primera is fitted with a pressure-type radiator cap. Depending on engine and market, the cap sits either on the radiator neck (common on late P11 with SR20) or on a pressurised reservoir/degas tank (seen on early P12 with QR20). In both cases, the vehicle requires a correctly rated pressure cap as part of normal cooling system operation.

A healthy radiator cap does more than keep coolant from sloshing out. It seals the system, holds pressure (typically around 0.9–1.1 bar/90–110 kPa for this model family) to lift the boiling point, and uses a two-way valve to purge excess pressure when hot and draw coolant back from the bottle as it cools. That steady pressure helps prevent hot spots, cavitation and hose collapse, and keeps the 2001 Primera running sweet under the bonnet on long, hot Kiwi or Aussie drives.

For servicing, it’s smart to inspect the cap at every coolant change or major service. Look for a tired spring, perished or flattened rubber seals, corrosion on the neck, and any white/green crust that hints at dried coolant. Symptoms of a crook cap include random temperature swings, coolant loss to the overflow, gurgling after shut-down, or hoses that collapse as the engine cools.

Replacement is inexpensive and worth doing every 5 years/100,000 km, or immediately if a pressure test shows it won’t hold its rated value. Use the rating specified on the existing cap or in the owner’s/service manual: many P11 SR20 cars use 0.9 bar, while some early P12 QR20 setups specify around 1.1 bar. Don’t “upgrade” pressure on a whim—hoses, radiator cores and heater circuits are designed for a particular load.

When fitting a new cap, only remove the old one with the engine stone cold. Crack it slowly with a rag to release any residual pressure. Top up with the correct premixed Nissan Long Life Coolant (or equivalent silicate-free formula), set the heater to hot, run the engine to operating temp, squeeze the upper hose to burp air, and recheck the level in the bottle to the MAX mark. After a few drives, have a peek for any seepage around the neck and ensure the cap’s gasket is seating cleanly. Keeping a spare cap in the boot isn’t a bad shout either—small part, big peace of mind.

• Typical cap pressure range for this model family: 0.9–1.1 bar (90–110 kPa)
• Inspect at each service, replace at 5 years/100,000 km or if test fails
• Location varies: radiator neck (P11) or pressurised reservoir (early P12)

Popular questions

What pressure radiator cap does a 2001 Nissan Primera use?
Most late P11 SR20 models use a 0.9 bar (90 kPa) cap, while early P12 QR20 setups often specify around 1.1 bar (110 kPa). The correct rating is printed on the cap and listed in the service manual—match that value to avoid over- or under-pressurising the system.

Where is the radiator cap on a 2001 Primera?
On P11 cars it’s usually on the radiator neck under the bonnet. On early P12 models, the cap often sits on a pressurised plastic reservoir (degas tank) instead. If there’s no cap on the radiator itself, follow the upper hose to find the reservoir-mounted cap.

How often should the radiator cap be replaced?
As a rule of thumb, every 5 years or 100,000 km, or sooner if a pressure test shows it won’t hold spec. Replace immediately if you see cracked rubber, a weak spring, or evidence of leaks or overheating.