Parts for your 2013 Toyota Bb-Radiator cap

2013 Toyota bB radiator cap – what it does and when to replace it

Technical sources confirm the 2013 Toyota bB is fitted with a conventional pressure-type radiator cap. The Toyota Electronic Parts Catalogue for the QNC2# series (2010–2016) lists a “Cap Sub-Assy, Radiator” on the radiator upper tank, and Toyota’s bB repair manual for the same series specifies a cap pressure test of roughly 108 kPa (about 1.1 bar). That means a radiator cap is relevant and used on the 2013 Toyota bB.

On the 2013 Toyota bB, the radiator cap does more than seal the top of the radiator. It holds a set pressure so the coolant’s boiling point is raised, keeps the system stable on hot days or long climbs, and manages coolant flow to and from the overflow bottle as things heat up and cool down. It’s effectively a tiny pressure regulator and a one-way valve in one, helping the bB avoid overheating and air pockets under the bonnet.

As part of regular servicing of the 2013 Toyota bB radiator cap, it pays to check the cap every service or two. Look for perished or flattened rubber seals, a sticky or gritty spring, and crusty deposits on the sealing surfaces. A workshop can pressure-test the cap to the factory spec (around 108 kPa/1.1 bar) to be sure it still holds and releases correctly. If there’s any doubt, replace it—caps are inexpensive insurance against overheating dramas.

When replacing, match the pressure rating to OE spec (typically 1.1 bar for the bB) and choose a quality cap that meets Toyota’s requirements. Only open the cap when the engine is stone cold, wrap it in a rag and crack it slowly to release any residual pressure. After refitting, top up the radiator (not just the overflow bottle) with Toyota Super Long Life Coolant (pink) and set the reservoir to the FULL mark. Don’t mix coolant types or colours, and bleed out air if required.

Common clues the cap’s had its day include:

• Unexplained coolant loss or stained overflow bottle
• Overheating in traffic but not on the open road
• Collapsed radiator hoses after cool-down or a hard top hose soon after cold start

Treat the cap like any other wear item: inspect routinely, replace every 5 years or 80,000–100,000 km, or sooner if test results or seal condition say so. It’s a small part that makes a big difference to the bB’s cooling reliability.

Popular questions

What pressure radiator cap does a 2013 Toyota bB use?
Most 2013 bB models use a 1.1 bar (about 108 kPa) pressure cap. Check the stamping on the existing cap or confirm via the Toyota parts catalogue for the specific QNC2# variant to be sure.

How often should the radiator cap be replaced on a 2013 bB?
Have it inspected at every service and pressure-tested periodically. As a rule of thumb, replace the cap about every 5 years or 80,000–100,000 km, or immediately if the seals are damaged, the spring sticks, or it fails a pressure test.

Can coolant be topped up through the radiator cap on the bB?
Yes—when the engine is completely cold. Fill the radiator to the neck, then set the overflow bottle to the FULL mark. Use Toyota Super Long Life Coolant (pink) and avoid mixing different coolant types.