Parts for your 2015 Ford Mondeo-Radiator cap

2015 Ford Mondeo radiator cap – is it actually a thing?

Short answer: a traditional radiator cap isn’t used on the 2015 Ford Mondeo (MD/Mondeo Mk5). Ford’s own technical literature points to a sealed, pressurised cooling system that vents and fills via a remote coolant expansion (degas) tank with its own pressure cap. The 2015 Mondeo Owner’s Manual shows topping up at the expansion tank, not the radiator neck, and the Ford Workshop Manual (Section 303-03, Engine Cooling) specifies a “degas bottle” and “coolant expansion tank cap”, not a radiator cap on the core itself.

Why no radiator cap on the radiator? Modern Mondeo engines use a pressurised expansion tank placed high in the engine bay. That tank is the single fill point and the spot where pressure is regulated. The radiator is part of a closed loop and doesn’t need a cap neck anymore.

• Better air separation and self-bleeding: the degas tank helps purge air and keeps coolant volume stable.
• Consistent pressure control: the cap on the tank manages system pressure without hot spots at the radiator.
• Packaging and safety: no need to lean over a hot radiator, access is at the reservoir under the bonnet.

What this means for owners is simple: treat the “radiator cap” as the expansion tank pressure cap. It does the same essential job—holding pressure so the boiling point rises, then venting safely if pressure gets too high.

Servicing tips for the Mondeo’s pressure cap:

• Only open when stone cold. Even warm coolant can flash to steam.
• Check the cap at each service (or about every 12 months/15,000 km). Look for hardened or cracked rubber seals, damaged threads, or crusty deposits.
• If you’ve had an overheating event, replace the cap—its spring and seals can be cooked.
• Match the pressure rating printed on the existing cap. The wrong rating can cause overflow, hose collapse, or slow warm-up.
• Top up with the coolant type specified in the owner’s manual and mix ratio appropriate for local climate.

Tell-tales of a dodgy cap include frequent coolant loss with no visible leaks, hoses that collapse after cool-down, fluctuating temp readings, or the reservoir overflowing. Swapping a tired cap is cheap insurance against bigger dramas like warped heads or a split heater core.

Technical references: 2015 Ford Mondeo Owner’s Manual (Cooling System/Expansion Tank instructions) and Ford Workshop Manual Section 303-03 (Engine Cooling) describing the degas/expansion tank and cap.

Popular questions

Where is the radiator cap on a 2015 Ford Mondeo?
There isn’t a cap on the radiator itself. The pressure cap is on the coolant expansion (degas) tank under the bonnet. It’s the black plastic cap with a warning symbol and a pressure rating. Only open it when the engine is completely cool.

What pressure cap should the 2015 Mondeo use?
Use a cap with the same kPa/psi rating printed on your current cap. Many Mondeo engines run a cap in the ~140–150 kPa range, but always match what’s specified for your exact engine. The wrong pressure can cause leaks or poor heater performance.

How should coolant be topped up on this model?
When the engine is cold, slowly loosen the expansion tank cap to release any residual pressure. Top up to the MAX mark with the coolant type recommended in the owner’s manual. Refit the cap firmly, start the engine, bring it to operating temperature with the heater on hot, then let it cool and re-check the level.