Parts for your 2017 Mitsubishi Outlander-Radiator cap

2017 Mitsubishi Outlander radiator cap — what it does and how to look after it

Based on Mitsubishi Motors factory information (2016–2018 Outlander Service Manual, Group 14: Cooling System) and dealer parts catalogues for the 2017 model year, the petrol and diesel Outlander variants use a pressurised cooling system with a radiator pressure cap mounted on the radiator neck. The Outlander PHEV uses a pressure cap on the coolant reservoir (degas bottle) rather than on the radiator itself. Either way, a pressure-type cap is fitted on 2017 Outlander models, so a “radiator cap” is relevant for servicing.

The radiator cap on a 2017 Mitsubishi Outlander is a small part with a big job. It seals the cooling system and holds a set pressure (typically around 108 kPa/1.1 bar) so the coolant’s boiling point is raised, helping the engine stay happy in Aussie and Kiwi conditions. Inside the cap are two valves: a pressure valve that lets excess pressure vent to the overflow bottle, and a vacuum valve that draws coolant back in as the engine cools. That back-and-forth keeps air out and coolant circulating properly.

During regular servicing, it’s smart to give the cap a proper look. Under a cold bonnet, check the rubber seal for cracking or flattening, make sure the spring feels firm, and inspect the radiator filler neck for corrosion or crusty deposits. A dodgy cap can cause coolant loss, hard-to-trace overheating at highway speeds, collapsed upper hoses after cool-down, or constant top-ups.

• Replace the cap if the seal is perished, the spring action is weak, or there’s staining around the filler neck.
• Stick with the correct pressure rating specified for the Outlander, too low and it can boil early, too high and it stresses hoses and the radiator.
• Check the overflow hose for splits and ensure the bottle level sits between the marks when cold.

As a rule of thumb, have the radiator cap inspected at every service and consider replacement every 5–7 years or around 100,000 km, sooner if there are any symptoms. When refilling coolant, use the Mitsubishi-approved long-life coolant specified for the vehicle and bleed air as outlined in the service manual.

Safety tip: never open the cap when hot. Let the engine cool fully, use a rag, and crack it slowly to release any residual pressure.

Popular questions about 2017 Mitsubishi Outlander radiator caps

Does a 2017 Outlander have a radiator cap?
Yes. Petrol and diesel models have a pressure cap on the radiator itself. The PHEV uses a pressure cap on the coolant reservoir instead. Both serve the same purpose—sealing and pressurising the system to lift the coolant’s boiling point and manage expansion and contraction.

What pressure rating should the cap be?
Most 2017 Outlander variants specify roughly 108 kPa (1.1 bar). Always confirm against the owner’s manual or the under-bonnet label to match the exact spec for the engine variant.

Can a bad radiator cap cause overheating?
It can. A weak cap can let pressure drop, which lowers the coolant’s boiling point and can lead to boil-over or gradual loss. It might also pull air into the system on cool-down. If there’s unexplained coolant loss, collapsed hoses after shutdown, or overheating at speed, the cap is a cheap part to test or replace first.