Parts for your 1998 Nissan Navara-Radiator cap

1998 Nissan Navara radiator cap — purpose, care and replacement

Yes, a radiator cap is fitted to the 1998 Nissan Navara (D22) and it’s a serviceable item. Technical sources back this up: the Nissan D22 Workshop Manual (Cooling System, CO section) specifies a radiator cap inspection and an opening pressure of roughly 78–98 kPa (0.8–1.0 kg/cm², about 11–14 psi). The 1998 Nissan Frontier (D22) Service Manual’s cooling section also outlines radiator cap testing. Australian parts catalogues from well-known manufacturers list a 0.9 bar (13 psi) cap for D22 Navara models. So the radiator cap is relevant to routine servicing on a 1998 Navara.

On a ’98 Navara, the radiator cap does more than just seal the filler neck. It manages system pressure so coolant boils at a higher temperature, keeps the cooling circuit topped via the overflow bottle as things heat up and cool down, and prevents air sneaking back in. A healthy cap helps the ute hold steady temps on hot days, towing, or low-range work.

Good maintenance is simple and pays off big time. Only check or remove the cap when the engine is completely cold. Look for perished rubber seals, a sticky or crooked spring, or crusty deposits on the seat. If you’ve got access to a pressure tester, confirm the rating—most D22s use around 0.9 bar (13 psi)—and make sure it holds pressure without bleeding down. Any doubt? Replace it. Caps are inexpensive compared with heads and head gaskets.

Best practice on a 1998 Navara is to replace the radiator cap whenever you do a major coolant service or every 3–5 years/60,000–100,000 km, especially if the vehicle works hard in Aussie or Kiwi heat. Match the pressure rating stamped on the old cap or as per the workshop manual, choose OEM or quality aftermarket, and make sure the neck and seal faces are clean before fitting. After replacement, run the engine to operating temp with the heater on, let it cool fully, and recheck the overflow level to ensure proper draw-back from the reservoir.

• Common signs the cap’s tired: overflow bottle constantly full or empty, slow warm-up and sudden spikes, coolant stains around the neck, collapsed top hose after cool-down, or a sweet smell under the bonnet.
• Never top up with the engine hot. Burns aren’t worth it—wait until it’s stone cold.

Popular questions

What pressure radiator cap suits a 1998 Navara?
Most D22 Navaras from this era use a 0.9 bar (13 psi) cap. Check the stamping on your existing cap or the workshop manual specs to confirm. Using the correct pressure rating maintains the intended boiling point and protects hoses, radiator cores and seals.

How can they tell if the radiator cap is failing on a D22?
Look for coolant pushing into the overflow and not returning, staining or dampness around the filler neck, a top hose that collapses after cool-down, or creeping temperatures on climbs and tows. If a pressure test shows it won’t hold the rated pressure or the vacuum valve sticks, it’s due for replacement.

Is it safe to keep driving with a dodgy radiator cap?
Not recommended. A weak cap reduces the boiling point and can introduce air, triggering overheating under load. That risks warped heads and blown gaskets. Swapping in a correct, quality cap is cheap insurance compared with engine repairs.