2018 Subaru Forester Coolant Capacity & Type

The 2018 Subaru Forester cooling system holds approximately 7.9 to 8.2 quarts (7.5 to 7.8 liters) of coolant, though this can vary slightly with engine size.

Quick Answer

• Total Cooling System Capacity: 7.9 - 8.2 quarts (7.5 - 7.8 liters)
• OEM Coolant Spec: Subaru Super Coolant (Blue, HOAT, Subaru K0794YA001 Super Coolant or equivalent)
• Mix Ratio: 50/50 Pre-mixed

Capacity by Engine Option

Flush Interval

Subaru recommends a significantly longer flush interval for its Super Coolant. Always consult your owner's manual for the most precise figures, but general guidelines are:

• Normal Duty: Initial replacement at 137,500 miles (220,000 km) or 11 years, then every 75,000 miles (120,000 km) or 6 years thereafter.
• Severe Duty: While the Super Coolant has an extended life, frequent towing, driving in extreme temperatures, or dusty conditions may warrant more frequent inspection and potentially earlier replacement. Consider inspecting at 75,000 miles (120,000 km) or 6 years.

How to Refill & Bleed

Refilling and bleeding the cooling system on a 2018 Subaru Forester is crucial to prevent air pockets, which can lead to overheating.

1. Preparation: Ensure the engine is cool. Place a drain pan under the radiator draincock.
2. Drain: Open the radiator draincock and remove the radiator cap to allow the system to drain completely. For a full flush, you may want to open the engine block drain plugs if accessible (consult a service manual for exact locations).
3. Close & Fill: Close the draincock and block plugs. Fill the radiator reservoir with the specified Subaru Super Coolant (50/50 mix). Fill slowly to allow air to escape.
4. Bleed Air: Start the engine with the heater on full blast and the fan on low. Leave the radiator cap off. As the engine warms up, the thermostat will open, and coolant will begin to circulate. Squeeze the upper and lower radiator hoses several times to help dislodge air bubbles.
5. Maintain Level: Keep an eye on the coolant level in the radiator during this process, topping it off as necessary.
6. "Burp" System: The Forester, like many modern vehicles, can be prone to airlock. Some technicians find that raising the front end of the vehicle slightly helps air to escape. Run the engine until the cooling fans cycle on and off at least twice, adding coolant to maintain the proper level.
7. Check Reservoir: Once the engine is off and cooled down, recheck the coolant level in the reservoir and top off to the "FULL" mark if needed.
8. Final Checks: Keep an eye on the coolant level in the días following the refill, as small air pockets can still work their way out.

Common Cooling System Issues (2014-2018 Forester SJ Generation)

The SJ generation Subaru Forester, which includes the 2018 model year, is generally reliable, but some cooling system issues can arise:

• Thermostat Failure: A failing thermostat can cause the engine to overheat (stuck closed) or run too cool (stuck open). Symptoms include fluctuating temperature gauges or the engine taking a long time to warm up.
• Radiator Leaks: Over time, radiators can develop leaks, particularly at the plastic end tanks. This is often noticed as a sweet smell, visible coolant puddles, or a steadily dropping coolant reservoir level.
• Head Gasket Issues (Less Common for FB Engine): While older Subaru engines were notorious for head gasket failures, the FB-series engine (2.5L) used in the 2018 Forester is significantly more robust in this regard. However, failures can still occur, especially if the engine has been subjected to prolonged overheating. Symptoms can include external oil or coolant leaks near the cylinder heads, white smoke from the exhaust, or coolant contamination in the oil.
• Water Pump Leaks: The water pump, driven by the serpentine belt, can eventually develop leaks or bearing noise. A leaking water pump will be evident by coolant seepage from the pump's weep hole, or a grinding noise from the front of the engine.
• Coolant Temperature Sensor Failure: A faulty coolant temperature sensor can send incorrect readings to the engine control unit (ECU), leading to issues like poor fuel economy, rough idling, or the cooling fans operating incorrectly.

Regular maintenance and using the correct Subaru Super Coolant are key to preventing these issues and ensuring the longevity of your Forester's cooling system.

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