2018 Mercedes-Benz Sprinter Serpentine Belt Guide

Quick Answer

• Engine Option: 3.0L V6 OM642 Diesel Engine
• Serpentine Belt Length: 2413mm (95 inches)
• Rib Count: 7-rib
• OEM Belt Part Number: Mercedes-Benz 002-993-30-96
• Aftermarket Belt Cross-References: Gates K070950, Dayco 5070950, Continental 4070950
• Automatic Tensioner Part Number: Mercedes-Benz 642-200-13-70
• Idler Pulley Part Number: Mercedes-Benz 642-202-01-19

Belt Routing

Properly routing the serpentine belt on your 2018 Sprinter's 3.0L V6 diesel engine is critical for the function of all engine-driven accessories. An incorrectly routed belt can cause damage to the belt and the components. Before you remove the old belt, we strongly recommend taking a clear photograph of the existing belt routing from a couple of angles. This will provide an invaluable visual guide during installation.

The belt path is as follows:

1. The belt wraps around the main crankshaft pulley at the bottom of the engine.
2. From the crank pulley, the belt travels up to the A/C compressor.
3. Next, it goes around the smooth idler pulley.
4. From the idler, the belt routes to the alternator.
5. After the alternator, it wraps around the power steering pump pulley.
6. It then moves to the water pump.
7. Finally, the belt comes to the automatic tensioner, which maintains the correct belt tension, before returning to the crankshaft pulley.

How to Replace the Serpentine Belt

Replacing the serpentine belt on the OM642 engine is manageable for a DIYer with the right tools. The primary tool you'll need is a serpentine belt tool, which is a long, thin wrench with various socket and crow's foot attachments. A long-handled 3/8" drive breaker bar can also work to release the belt tension.

First, locate the automatic belt tensioner. You will see a square hole (typically 3/8") or a hex-shaped lug on the body of the tensioner. Insert your serpentine belt tool or breaker bar and rotate the tensioner to release the pressure on the belt. Once the tension is released, you can slip the belt off one of the pulleys (the topmost, smoothest pulley is often the easiest). Carefully finish removing the old belt, making sure not to let the tensioner snap back into place.

With the old belt removed, it is wise to inspect all the pulleys. Spin each one by hand. They should spin smoothly and silently. Any roughness, grinding noises, or wobble indicates a failing bearing, and the pulley (or the entire accessory, in some cases) should be replaced.

To install the new belt, carefully follow your photo and the routing description above. It's often easiest to leave the final placement for a smooth, non-lipped pulley like the water pump or idler. Once the belt is routed correctly on all the grooved pulleys, release the tensioner slowly to apply pressure, making sure the belt is seated properly in all the pulley grooves.

Replacement Interval

Mercedes-Benz recommends inspecting the serpentine belt at regular service intervals. While there isn't a strict replacement mileage that fits all conditions, a general guideline for the 2018 Sprinter is to replace the belt every 60,000 to 80,000 miles, or every 6-8 years, whichever comes first. If the van is used in severe conditions (heavy loads, extreme temperatures, dusty environments), more frequent inspections and earlier replacement may be necessary.

Signs of a Failing Belt or Tensioner

Your Sprinter will give you several warning signs that the serpentine belt or its tensioner requires attention. Ignoring these can lead to a breakdown and potentially expensive engine damage.

• Squealing or Chirping Noises: This is the most common sign of a worn or contaminated belt. The noise may be more noticeable on cold starts or during acceleration.
• Visible Wear on the Belt: Inspect the belt for cracks, fraying, glazing (shiny spots), or missing ribs. Any visible damage means the belt should be replaced immediately.
• "Belt Slap" Noise: A flapping or slapping sound from the engine bay often points to a failing automatic tensioner that is no longer able to maintain consistent pressure.
• Component Malfunction: Since the serpentine belt drives multiple accessories, you may notice issues like a flickering battery light (alternator), stiff steering (power steering), or the engine temperature rising (water pump).

If you're experiencing any of these symptoms, a thorough inspection of the entire serpentine belt system is crucial.

Find a trusted shop on Repairius.