Parts for your 2021 Mitsubishi Eclipse cross-Radiator cap

Radiator cap for the 2021 Mitsubishi Eclipse Cross

For the 2021 Mitsubishi Eclipse Cross, a radiator cap is indeed fitted and relevant. This is supported by Mitsubishi technical literature: the Eclipse Cross (GK) Workshop Manual includes a radiator cap inspection and pressure test procedure (around 108 kPa/1.1 bar), and the Owner’s Manual cooling system cautions specifically reference the radiator cap. Genuine Mitsubishi parts catalogues also list a dedicated radiator cap for GK-series Eclipse Cross models. So yes—this model uses a conventional pressurised radiator cap working with an overflow bottle.

The radiator cap on a 2021 Eclipse Cross does more than just seal the top of the radiator. It regulates cooling system pressure to lift the coolant’s boiling point, helping the 1.5T MIVEC engine keep its cool in Aussie and Kiwi conditions. Inside the cap are pressure and vacuum valves. Under heat, the pressure valve lets expanding coolant move to the overflow bottle, as it cools, the vacuum valve draws coolant back, keeping the system topped and free of excess air.

During regular servicing, it’s smart to give the cap a once-over. Look for brittle rubber seals, a sticky or weak spring, corrosion on the seat, or crusty deposits around the filler neck. If there’s access to a tester, have the cap pressure-checked to its rated value (often stamped on the cap, commonly 108 kPa/1.1 bar for Mitsubishi applications). A cap that can’t hold spec can cause boil-over, random temperature swings, and coolant loss.

• Only remove the cap when the engine is stone cold—never when hot.
• Top up at the radiator neck first (cold engine), then set the overflow bottle to the “FULL” mark.
• Use the correct Mitsubishi-approved long-life coolant and the right mix ratio.
• After coolant service, follow the workshop air-bleeding procedure to prevent hot spots.

There’s no hard-and-fast replacement interval for the cap, but many techs treat it like a low-cost insurance item every 5 years or at the first sign of trouble. Stick with an OEM-spec cap matching the factory pressure rating. If hoses collapse as the engine cools, there’s dried coolant around the neck, or the heater goes cold at idle, the cap is high on the suspect list. A healthy radiator cap is small money for big peace of mind on the Eclipse Cross.

Popular questions about the 2021 Mitsubishi Eclipse Cross radiator cap

Does the 2021 Eclipse Cross have a radiator cap or just a coolant bottle?
Yes, it has a proper radiator cap on the radiator neck, plus a separate translucent overflow bottle with a non-pressurised cap. The factory literature for the GK-series confirms a pressurised cap and outlines testing procedures. Always check the handbook for exact under-bonnet locations for your build.

What pressure rating should the radiator cap be?
Most Eclipse Cross caps are rated around 108 kPa (1.1 bar). The exact rating is stamped on the cap. Running the wrong pressure can trigger early boil-over (too low) or stress hoses and seals (too high), so match the factory spec.

When should the radiator cap be replaced?
There’s no set mileage, but it should be tested at coolant-change intervals and replaced if it fails a pressure test, shows perished seals, sticks, or there’s persistent coolant loss. Many owners opt to replace it preventatively at about five years.