The simplest sign is to check the translucent expansion reservoir against the MIN and MAX marks, plus any dash warnings or overheating symptoms. If the level is low or you notice leaks, top up with the correct coolant and inspect the system for issues.
This guide explains how to confirm coolant levels, interpret common signs of low coolant, safely top up, and what to do if you detect a leak or persistent low readings on your Subaru.
Common signs that coolant is low
Look for the most frequent indicators that the cooling system may be running low on coolant. These cues help you decide whether to inspect the reservoir and possibly top up.
- Dashboard coolant warning light appears on some Subaru models.
- Engine temperature gauge climbs toward the overheating zone or stays hot for longer than normal.
- Steam, fogging, or a hot, sweet smell coming from the engine bay.
- Visible leaks or a puddle under the front of the vehicle.
- Oil appears milky or coolant odor is detected in the crankcase, which can indicate a leak into the engine.
If you notice any of these signs, proceed to safely verify the coolant level and inspect for leaks. Early detection helps prevent engine damage.
How to check the coolant level safely
Before checking, ensure the engine is cold and the vehicle is on level ground. This prevents scalding and gives an accurate reading.
- Park on level ground and allow the engine to cool completely before opening any caps.
- Open the hood and locate the translucent expansion (overflow) reservoir; read the coolant level against the MIN and MAX markings.
- Inspect the reservoir and nearby hoses for cracks, bulges, or signs of leakage.
- Check the coolant’s appearance; it should be bright and properly colored (not dark, rusty, or muddy).
- If the level is between MIN and MAX, you may not need to add coolant right away; if it’s at or below MIN, plan a top-up with the correct product.
After performing these checks, you’ll have a clear sense of whether coolant is low and whether there might be a leak or other issue requiring attention.
What to do if coolant is low or you detect a leak
Take these steps when you confirm a low level or see a leak. Safety first: do not open the radiator cap while the engine is hot.
- Use only Subaru-approved Long Life Coolant (ethylene glycol–based) or a compatible Subaru coolant in a 50/50 premixed solution with distilled water.
- With the engine cold, remove the reservoir cap, and slowly add coolant up to the MAX line.
- Reinstall the cap, start the engine, and run it to operating temperature to help bleed air from the system; then recheck the level after it cools.
- Inspect for leaks around the radiator, hoses, thermostat housing, water pump, and reservoir; address any visible leaks promptly.
- If the level remains low after topping up or coolant keeps leaking, schedule service promptly to diagnose potential hose, radiator, or gasket issues.
Maintaining proper coolant levels helps prevent overheating and protects the engine. If you’re unsure or uncomfortable performing checks, seek a qualified technician for a diagnostic.
Maintenance tips and safety
Regular maintenance and careful handling of coolant reduce the risk of overheating and engine damage. Follow these best practices to keep your Subaru’s cooling system in good shape.
Choosing the right coolant for your Subaru
Use Subaru’s Long Life Coolant (ethylene glycol–based) in a 50/50 premixed solution with distilled water, unless your owner’s manual specifies an alternative. Do not mix different coolant types, and avoid using plain water as a long-term substitute.
Bleeding and air pockets
Air pockets can cause inaccurate readings or overheating. If you suspect air in the system, consult the owner’s manual for the correct bleeding procedure for your model, or have a technician perform it. Never attempt to force coolant into a hot engine.
Summary
To tell if a Subaru’s coolant is low, check the expansion tank against the MIN/MAX marks when the engine is cold, watch for dash warnings or overheating, and look for leaks or steam. If low, top up with the correct 50/50 Subaru coolant and inspect for leaks or signs of a failing component. Regular maintenance and safe handling, including following the bleeding procedure if needed, help prevent overheating and engine damage.