2018 Mercedes-Benz Metris Serpentine Belt: Routing, Parts, and Replacement

Quick Answer

• Belt Length: Approximately 2110 mm
• Rib Count: 6-rib
• OEM Belt PN: Mercedes-Benz A0039930096
• Aftermarket Cross-references:
  • Gates K060830
  • Dayco 5060830
  • Continental Elite 4060830
• Auto-Tensioner PN: Mercedes-Benz A2742000270 (Verify with VIN)
• Idler Pulley PN: Mercedes-Benz A2742020019 (Verify with VIN)

Belt Routing

The serpentine belt on your 2018 Mercedes-Benz Metris follows a specific path to drive various accessories. Before you begin any work, it is highly recommended to take a clear photograph of the existing belt routing. This will serve as an invaluable reference during reinstallation.

For the 2.0L M274 engine, the belt routing typically follows this path:

1. Starting from the Crankshaft Pulley (the largest pulley at the bottom, directly driven by the engine).
2. The belt then goes up to the A/C Compressor Pulley (usually located on the lower passenger side).
3. From the A/C compressor, it wraps around an Idler Pulley (a smooth pulley, often used to guide the belt and maintain tension in a specific area).
4. Next, the belt travels to the Alternator Pulley (typically high on the driver's side, responsible for charging the battery).
5. From the alternator, it makes its way to the Power Steering Pump Pulley (if equipped, often located below the alternator or on the driver's side).
6. It then goes to the Water Pump Pulley (usually central or slightly to one side, responsible for coolant circulation).
7. Finally, the belt routes around the Automatic Tensioner Pulley (this pulley applies constant tension to the belt and has a square drive hole for a serpentine belt tool or breaker bar).

How to Replace the Serpentine Belt

Replacing the serpentine belt on your 2018 Mercedes-Benz Metris requires a few basic tools and a careful approach.

1. Safety First: Ensure the engine is turned off and cool. Disconnect the negative battery terminal for added safety.
2. Locate the Tensioner: Identify the automatic tensioner pulley. It will have a square hole (usually 3/8-inch or 1/2-inch) or a hex bolt head at its pivot point.
3. Relieve Tension: Insert a serpentine belt tool or a 3/8-inch breaker bar into the square hole of the tensioner. Slowly rotate the tensioner to relieve tension on the belt. This will allow you to slip the belt off one of the pulleys.
4. Remove the Old Belt: Once tension is relieved, carefully slide the old belt off the pulleys, starting from one of the easier-to-reach pulleys (e.g., alternator or idler).
5. Inspect Pulleys: Before installing the new belt, inspect all pulleys for any signs of wear, damage, or excessive play. Worn pulleys can quickly damage a new belt.
6. Install the New Belt: Following the routing diagram you photographed earlier (or the text-based description above), carefully route the new belt around all pulleys. Ensure the ribbed side of the belt sits correctly in the ribbed grooves of the pulleys and the smooth side rides on smooth pulleys.
7. Final Tensioning: Once the belt is routed correctly on all pulleys except for one (often the tensioner itself or another easily accessible pulley), again use your serpentine belt tool or breaker bar to relieve tension on the tensioner. Slip the belt completely onto the final pulley. Slowly release the tensioner to apply proper tension to the new belt.
8. Double-Check: After installation, visually inspect the entire belt path to ensure it is seated correctly on all pulleys and has no twists or kinks.
9. Reconnect Battery: Reconnect the negative battery terminal.
10. Test: Start the engine and listen for any abnormal noises. Observe the belt's operation for a few minutes.

Replacement Interval

Mercedes-Benz generally recommends inspecting the serpentine belt at every service interval. While there isn't a rigid mileage-based replacement interval for the serpentine belt, a good rule of thumb is to consider replacement every 60,000 to 100,000 miles, or every 5-7 years, whichever comes first. However, this can vary significantly based on driving conditions and climate. Always refer to your vehicle's owner's manual for specific recommendations.

Signs of a Failing Belt or Tensioner

Promptly addressing issues with your serpentine belt or tensioner can prevent more significant problems and costly repairs.

Signs of a Failing Serpentine Belt:

• Squealing or Chirping Noises: This is one of the most common signs, especially when starting the engine or turning the steering wheel.
• Visible Cracks or Fraying: Inspect the belt's ribbed side for cracks, splits, or frayed edges. Also, look for glazing or a shiny appearance on the belt.
• Missing Ribs or Chunks: Any missing material from the belt indicates severe wear and an imminent failure.
• Loss of Power to Accessories: If the belt is slipping or failing, you might notice the power steering becoming heavy, the A/C not blowing cold, or the battery light illuminating (due to the alternator not charging effectively).

Signs of a Failing Automatic Serpentine Belt Tensioner:

• Excessive Belt Noise: While a failing belt can squeal, a failing tensioner can also contribute to belt noise due to improper tension.
• Vibration or Wobble: Observe the tensioner pulley while the engine is running (from a safe distance). If it's vibrating excessively or wobbling, the internal spring or bearing may be failing.
• Belt Looseness: If the tensioner is no longer applying adequate pressure, the belt may appear visibly loose.
• Sticking or Seizing: If the tensioner doesn't move freely when attempting to relieve tension, it may be seized or corroded.

Always ensure to verify part numbers with a reputable parts supplier or Mercedes-Benz dealership using your vehicle's VIN to ensure proper fitment, as variations can occur.

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