2021 Mercedes-Benz Metris Coolant Capacity & Type Guide

The 2021 Mercedes-Benz Metris holds approximately 9.5 quarts (9.0 liters) of engine coolant to keep its 2.0L turbocharged inline-4 engine operating at optimal temperatures. As an ASE-certified master technician, I regularly service these versatile commercial and passenger vans. Proper cooling system maintenance is critical to ensuring the longevity of the M274 engine equipped in the Metris. Using the correct coolant specification and bleeding the system properly will prevent catastrophic overheating and costly downtime.

Quick answer

• Total cooling system capacity: Approximately 9.5 quarts (9.0 liters).
• OEM coolant spec: Mercedes-Benz uses a Si-OAT (Silicated Organic Acid Technology) chemistry for this generation. You must use coolant meeting MB-Approval 325.6 (concentrate) or MB-Approval 326.6 (pre-mixed), which is typically pink or violet in color. Note: Always verify the color of your factory fill, as some earlier formulations used MB 325.0 (blue).
• Mix ratio: A 50/50 mixture of concentrated coolant and distilled water (or use a 50/50 pre-mixed formula). Do not use tap water, as the minerals will damage the internal cooling passages.

Capacity by engine option

For the 2021 model year in the North American market, the Metris is exclusively offered with a single powertrain.

Note: Capacities are approximate and include the engine block, radiator, heater core, and reservoir. Always fill to the "MAX" line on the expansion tank when cold.

Flush interval

Mercedes-Benz utilizes long-life coolant in the Metris, but it is not a "lifetime" fluid. Over time, the protective additives break down, leading to corrosion and sludge build-up.

• Normal Duty: Replace the coolant every 150,000 miles or 15 years, whichever comes first.
• Severe Duty: For Metris vans used for towing, heavy delivery routes, or excessive idling (such as fleet or shuttle use), I strongly recommend flushing the coolant every 100,000 miles or 10 years to maintain maximum protection.

How to refill & bleed

The M274 engine in the Metris can be notoriously stubborn to bleed using traditional methods due to its complex cooling circuit and turbocharger coolant lines. Trapped air pockets will cause localized boiling and erratic heater performance.

1. Drain the system: With the engine cold, remove the expansion tank cap. Locate the radiator drain petcock at the bottom of the radiator, open it, and catch the old coolant in a drain pan.
2. Vacuum fill (Highly Recommended): As a master technician, I strongly advise using a vacuum coolant refill tool (Airlift) for this vehicle. Connect the vacuum tool to the expansion tank, pull a vacuum on the system (which also tests for leaks), and allow the tool to suck the new 50/50 coolant mixture directly into all the voids.
3. Manual bleed (If vacuum is unavailable): Fill the expansion tank slowly to the MAX mark. Leave the cap off.
4. Run the engine: Start the engine and turn the climate control heater to the maximum temperature with a low fan speed.
5. Bleed the air: Rev the engine slightly to around 2,000 RPMs to circulate the coolant. Top off the expansion tank as the level drops. Keep a close eye on the temperature gauge.
6. Final check: Once the thermostat opens (indicated by the upper radiator hose getting hot) and warm air blows from the cabin vents, top off the reservoir, install the cap, and test drive. Recheck the level the next morning when the engine is completely cold.

Common cooling system issues

The 2021 Metris is generally robust, but the M274 engine platform does have a few cooling system quirks that technicians look out for:

• Water Pump Leaks: The mechanical water pump can develop weep hole leaks or bearing play as mileage increases. A slow drop in coolant level is often the first sign.
• Plastic Thermostat Housing: Like many modern European vehicles, the Metris uses a plastic thermostat housing that can become brittle and crack due to thousands of thermal cycles.
• Turbocharger Coolant Lines: The O-rings on the turbocharger coolant feed and return lines can degrade and seep coolant onto the hot exhaust, causing a distinct sweet syrup smell even if you don't see a puddle on the ground.

Taking care of your cooling system is the easiest way to keep your Metris on the road and out of the shop. If you suspect a leak or need a professional flush, find a trusted shop on Repairius.