Parts for your 2017 Subaru Outback-Radiator cap

2017 Subaru Outback radiator cap — what it does and how to look after it

Based on technical references such as the 2017 Outback Owner’s Manual and Subaru’s factory workshop manual for the 2015–2019 Outback range, this model does use a pressure-type radiator cap. It’s typically mounted on the coolant filler/header tank at the highest point under the bonnet rather than directly on the radiator neck. The overflow bottle nearby uses a non-pressurised cap. So yes, a radiator-cap is relevant to the 2017 Subaru Outback’s cooling system.

The radiator cap is a small bit of kit that does a big job. It seals the cooling system and holds a set pressure so coolant can run hotter without boiling, which keeps the Outback happy in Aussie and Kiwi conditions. Inside, a spring-loaded valve lifts if pressure gets too high, sending excess coolant to the overflow bottle. As things cool down, a second valve lets coolant draw back in, preventing hoses from collapsing and keeping the system full. It’s also the proper fill point for bleeding and topping up after a service.

Cap condition matters. A tired spring, nicked seal, or crusty seat can cause slow overheating, random coolant loss, hard cold starts from air pockets, or a heater that goes lukewarm. During routine servicing, the cap should be checked when the engine is stone cold: look for perished rubber, corrosion, weak spring tension, or staining around the neck. If anything’s suspect, replace it—caps are inexpensive insurance for the FB25 and EZ36 cooling systems fitted to 2017 Outbacks.

• Never open the cap hot. Wait until cold, then crack it slowly to release any residual pressure.
• Use the correct pressure rating and genuine-equivalent spec for the exact VIN/engine, mixing ratings can upset system behaviour.
• After cap replacement or a coolant change, fill at the filler tank and bleed per the workshop procedure to avoid trapped air.

As a practical rule, Outback owners often replace the cap preventatively at a scheduled coolant change or when any cooling quirk appears. Keeping the cap fresh helps protect the water pump, head gaskets, and heater core, and saves headaches on long kilometres.

Popular questions

Where is the radiator cap on a 2017 Subaru Outback?
The pressure cap sits on the coolant filler/header tank under the bonnet, usually at the top and slightly to one side. The radiator itself may not have a neck. The nearby overflow bottle uses a simple non-pressurised lid.

What pressure rating cap does it use?
The correct rating depends on engine and market spec. Many Subaru caps in this era are around 1.1 bar, but owners should match the cap to the exact part number or handbook listing for their vehicle to ensure proper pressure control.

How often should the cap be replaced?
There’s no strict interval. Inspect the cap at every service and replace it if the seal is cracked, the spring feels weak, there’s corrosion on the seat, or any cooling issues appear. Many owners choose to renew the cap at coolant change time for peace of mind.