Parts for your 2015 Ford Fiesta-Radiator cap

2015 Ford Fiesta radiator cap — what’s actually fitted

On the 2015 Ford Fiesta there isn’t a traditional cap on the radiator itself. Instead, the car uses a sealed radiator and a remote pressurised coolant expansion (degas) bottle with a pressure cap on that reservoir. In other words, “radiator cap” isn’t a separate part on the radiator for this model — the pressure control and filling point live on the plastic coolant tank.

Referencing technical sources: Ford’s 2015 Fiesta Owner’s Manual (Cooling system section) instructs checking and opening the coolant expansion tank cap, not a radiator cap. The Ford Workshop Manual (WSM) for 2015 Fiesta, Section 303-03 (Engine Cooling), diagrams a sealed radiator with a degas bottle and pressure cap. Major parts catalogues used in workshops (e.g., Motorcraft, Gates/Dayco application data) list a “coolant expansion tank cap” for this vehicle and no separate “radiator cap”.

Why this setup? Modern Fiestas use a remote degas bottle so the fill point is the highest spot in the system, which helps purge air, stabilises pressure, improves warm-up and packaging under the bonnet, and reduces the risk of scalding from older-style radiator necks. The radiator stays sealed, the cap on the reservoir is the pressure cap that keeps the coolant at the right boiling point and releases excess pressure to the overflow path when needed.

What owners should do instead of looking for a radiator cap: treat the expansion tank cap as the vital pressure cap and keep it in good nick. Only remove it when the engine is completely cold. Check the cap and the bottle at regular services or every 10,000–15,000 kilometres:

• Inspect the cap’s rubber seal and inner valve for cracks, flattening, or gritty deposits.
• Look for dried crusty coolant around the cap or bottle — that hints at a weak cap or poor sealing.
• If there’s recurring coolant loss, hoses that collapse as the engine cools, or overheating after a hard run, the cap could be dropping pressure.
• Use an OEM-quality replacement with the correct pressure rating (commonly around 140 kPa/20 psi for Fiesta). Avoid cheap caps that can vent too early.

Cap replacement is straightforward: when cold, unscrew the old cap, wipe the bottle’s neck clean, and install the new one hand-tight until it seats firmly. Don’t overtighten. If the vehicle has overheated, or the cap is older than five to seven years, proactive replacement is smart. Always top up with the correct Ford-approved coolant mix and never open the cap when hot.

Bottom line: there’s no separate radiator cap on a 2015 Ford Fiesta — the expansion tank cap is the hero here, and keeping it healthy helps keep the whole cooling system happy across Aussie and Kiwi conditions.

Popular questions about 2015 Ford Fiesta radiator caps

Where is the radiator cap on a 2015 Ford Fiesta?
There isn’t one on the radiator. The pressure cap is on the translucent coolant expansion (degas) tank under the bonnet. That’s the only cap you open to check or top up coolant — and only when the engine is cold.

What pressure cap does the 2015 Fiesta use?
It uses a pressurised expansion tank cap, typically around 140 kPa (20 psi). Always match the factory specification listed in the owner’s manual or parts catalogue and choose an OEM-quality cap to maintain the correct system pressure.

When should the cap be replaced?
Replace it if you notice coolant stains around the cap, recurring coolant loss, hoses collapsing after shutdown, or any overheating. Many techs also recommend replacing the cap after any overheating event or as preventative maintenance every 5–7 years.