Parts for your 2004 Toyota Caldina-Radiator cap

2004 Toyota Caldina radiator cap — what it does and when to replace it

Technical sources confirm the 2004 Toyota Caldina does use a radiator cap. The Toyota Electronic Parts Catalogue (Caldina T24# series, 2002–2007) and the Toyota Repair Manual cooling system section specify a pressurised cap across the range (ZZT241/246, AZT241/246, ST246W). Typical cap rating is 1.1 bar (about 108–110 kPa), with genuine cap part numbers commonly listed as 16401‑20353 or 16401‑31650 depending on radiator supplier. That means the radiator cap is relevant and serviceable on any 2004 Caldina.

On a 2004 Caldina, the radiator cap isn’t just a lid — it’s a pressure valve that keeps the cooling system sealed to raise the coolant’s boiling point, helping the engine run at the right temp even on hot Kiwi or Aussie summer days. It also manages expansion and contraction: as coolant heats and expands, the cap’s pressure valve lets excess flow to the overflow bottle, as things cool, the vacuum valve draws coolant back in, preventing hoses from collapsing and keeping the system topped up.

Because it’s working every heat cycle, the cap’s spring and rubber seals wear. A tired cap can cause slow coolant loss, gurgling, hard cold starts, or the overflow bottle filling and not returning. As part of routine servicing of a 2004 Caldina, a quick cap check under the bonnet is smart. Look for perished rubber, crusty deposits on the neck, a weak or sticky spring, or a cap that doesn’t “bite” firmly as it’s turned. If available, a pressure test to 1.1 bar will confirm if it holds and releases correctly.

Replacement guidance for owners and workshops:

• Use a cap rated 1.1 bar (Toyota spec for Caldina T24#), stick with genuine or a quality equivalent.
• Inspect every 12 months or 20,000 km, replace at the first sign of wear, or pre-emptively every 4–5 years.
• Never open a hot system — wait until fully cool. Wrap the cap with a rag and release slowly.
• Wipe the filler neck clean before fitting the new cap so the seal beds properly.
• If chasing overheating or random coolant loss, test or swap the cap before bigger tear-downs.

When refreshing coolant (Toyota Super Long Life Coolant, pink), bleeding air is easier with a good cap that holds spec pressure, helping the Caldina’s water pump and thermostat behave as designed.

Popular questions about 2004 Toyota Caldina radiator caps

What pressure rating should the Caldina’s radiator cap be?
For 2004 Caldina T24# models, Toyota specifies roughly 1.1 bar (about 108–110 kPa). Sticking to this rating keeps the coolant boiling point where the factory intended and protects hoses and the heater core. Higher-pressure caps aren’t recommended unless the entire cooling system has been set up for it.

Where is the radiator cap on the 2004 Caldina?
On most 2004 Caldina variants, the cap sits on the radiator filler neck near the top tank. The overflow bottle nearby is not pressurised, it’s there to catch expansion and return coolant as things cool.

How often should the cap be replaced?
With regular checks, many caps last years, but replacement every 4–5 years or around 100,000 km is a safe preventative step. If there are any signs of hardened rubber, corrosion, weak spring tension, or erratic coolant behaviour, replace sooner.