Parts for your 2002 Mitsubishi Pajero-Radiator cap

2002 Mitsubishi Pajero radiator cap — what it does and how to look after it

For the 2002 Mitsubishi Pajero (NM/NP series), a radiator cap is absolutely used and relevant. Mitsubishi’s workshop manual for the NM/NP cooling system (Group 14) specifies a pressurised cap with an opening pressure around 0.9 bar (13 psi). The Mitsubishi ASA parts catalogue and Australian fitment guides from well-known suppliers like Tridon and Gates also list dedicated radiator pressure caps for 2000–2006 Pajero models. So, whether it’s the 3.2 Di‑D diesel or the petrol V6, the Pajero relies on a proper radiator cap as part of its pressurised cooling system.

The cap’s job is simple but critical. It raises the coolant’s boiling point by holding pressure, helping the Pajero keep its cool while towing, off-roading, or slogging through summer heat. Inside the cap are two valves: a pressure valve that vents excess pressure safely to the overflow bottle, and a vacuum valve that draws coolant back into the radiator as the engine cools. That constant push-pull keeps air out, reduces hotspots, and protects hoses, the radiator, and the water pump from stress.

On a 2002 Pajero, the cap sits on the radiator’s filler neck. It should only be opened when the engine is stone cold. As part of regular servicing, it’s smart to:

• Inspect the cap every service for a cracked or flattened rubber seal, sticky or weak spring, and corrosion on the seating surfaces.
• Pressure-test the cap annually with a cooling-system tester to confirm it holds the specified rating.
• Replace the cap every 3–5 years, or immediately if it fails a pressure test.
• Match the factory pressure rating and neck type, don’t “upgrade” to a higher pressure cap unless a Mitsubishi bulletin specifically says so.

Classic clues that the cap’s had it include coolant pushing into the overflow bottle and not returning, a collapsed upper hose after cool-down, random overheating at highway speeds, and crusty deposits around the filler neck. When replacing, wipe the neck clean, seat the new cap squarely, and refill/bleed the cooling system with the correct ethylene-glycol coolant mix for Pajero. Run the heater on hot and let the engine reach operating temp to purge air. Taking a couple of minutes at service time to check this little part can save a big headache later.

Popular questions about 2002 Mitsubishi Pajero radiator caps

What pressure cap does a 2002 Pajero use?
Most 2002 Pajeros use a 0.9 bar (13 psi) radiator cap, as outlined in Mitsubishi’s NM/NP cooling-system specs. Always confirm against the under-bonnet label, existing cap markings, or a trusted parts catalogue by VIN.

Where is the radiator cap on a 2002 Pajero?
It’s on the radiator’s top filler neck. Some owners mistake the overflow bottle cap for the pressure cap, but the pressure cap is on the radiator itself. Only open it when the engine is fully cold.

How often should the cap be replaced?
Have it inspected every service and pressure-tested yearly. Many techs replace caps proactively every 3–5 years, or immediately if testing shows it won’t hold the correct pressure or the seals are tired.