Parts for your 2016 Subaru Impreza-Radiator cap

2016 Subaru Impreza radiator cap — purpose, care, and replacement

Technical sources confirm the 2016 Subaru Impreza does use a radiator cap. The Subaru Owner’s Manual for MY2016 (Cooling system section), the Subaru Service Manual for GJ/GP (Cooling > Radiator Cap Inspection), and the Subaru Genuine Parts catalogue list a 1.1 bar radiator cap for the FB20-powered Impreza, commonly referenced as P/N 45137AE001. These documents describe pressure testing of the cap (approx. 108 kPa), inspection of the seals, and correct fitment on the filler neck.

On this Impreza, the radiator cap does more than just close the filler neck. It regulates system pressure so coolant can run hotter without boiling, helping keep the engine stable on hot days, steep climbs, or when towing a light load. The spring-loaded pressure valve vents to the overflow bottle when pressure gets high, and the vacuum valve draws coolant back in as the system cools, preventing air pockets and collapsed hoses.

For routine servicing, it’s smart to have the cap inspected at each service interval. A workshop can pressure-test the cap to its rated 1.1 bar to confirm it holds and releases at the right points. If the rubber seals are cracked, the spring feels weak, or it fails a test, replace it straight away. Sticking with the OEM pressure rating is important, going higher can stress hoses and the radiator, while lower ratings can promote overheating and boil-over.

As a rule of thumb, many owners opt to replace the cap every 5 years or around 100,000 km, or sooner if there are symptoms. Only remove the cap when the engine is completely cold. Use a cloth, press down, and turn slowly. If coolant needs topping up, use the correct Subaru-approved coolant mix and keep the overflow bottle between the marks. Wipe the filler neck clean before refitting so the seal beds properly.

Signs the cap may be due for replacement include:

• Coolant loss with no obvious leaks, or frequent top-ups
• Collapsed upper radiator hose after cool-down
• Overheating in traffic, gurgling, or rusty/dirty-looking coolant
• Coolant smell around the front of the car after a drive

Using a genuine or high-quality equivalent cap keeps the 2016 Impreza’s cooling system happy, extends component life, and helps avoid costly overheating dramas.

Popular questions about the 2016 Subaru Impreza radiator cap

What pressure rating does the 2016 Impreza radiator cap use?
Most 2016 Imprezas use a 1.1 bar (approx. 108 kPa) cap. This is the common Subaru spec noted in the Service Manual’s radiator cap test procedure and on the OEM cap itself. For certainty, check the label on the existing cap or confirm by VIN with a Subaru parts counter (often P/N 45137AE001).

How often should the radiator cap be replaced?
Have it inspected at every service and replaced if it fails a pressure test, the seal looks tired, or there are cooling-system symptoms. As preventative maintenance, many workshops recommend replacement about every 5 years or 100,000 km.

Is it safe to open the radiator cap to check coolant?
Yes, but only when the engine is completely cold. Never open a hot system—pressurised coolant can cause burns. For quick checks between services, looking at the overflow bottle level is usually enough.