Mercedes-Benz Serpentine Belt Replacement Guide

Changing a Mercedes serpentine belt yourself costs under $50 in parts and needs one 17 mm socket on the tensioner pulley. A shop charges between $200 and $450 for the same work. The step worth not skipping is photographing the belt routing before you release the tension, even on cars that carry a routing diagram under the hood.

Over time, the belt can become worn and may need to be replaced to ensure the proper functioning of these systems. Replacing the serpentine belt on a Mercedes-Benz vehicle can be a relatively simple task for the experienced DIY mechanic. Still, it’s important to understand the process well and the necessary tools before attempting so. We will provide a step-by-step guide on how to replace the serpentine belt on a Mercedes-Benz, as well as tips and tricks to make the process as smooth as possible.

Do you hear a squealing noise on your Mercedes-Benz, power steering noise, poor air conditioner, or warning lights coming on? These symptoms may be caused by a worn or broken serpentine drive belt.

Symptoms

Some common symptoms that the serpentine belt may need to be replaced include:

• Squealing or chirping noise coming from the front of the vehicle
• Visible cracks or fraying on the belt
• The belt appears loose or misaligned
• Battery warning light, because the alternator stops charging
• Engine temperature rising, because the water pump on these engines is belt driven
• Loss of power steering or air conditioning

You must change your Mercedes-Benz serpentine belt if you notice symptoms such as squealing noise (most noticeable at startup). The serpentine belt may show signs of cracks and damaged ribs.  Other possible symptoms include power steering noise, poor air conditioner, and battery warning lights. Do not ignore your serpentine belt if it shows signs of damage. If the belt comes off when the engine is running, it can cause unnecessary damage to engine components.

These instructions on changing the Mercedes serpentine belt (also known as Drive Belt, Poly V Belt) apply to all Mercedes-Benz cars with six and eight-cylinder gasoline engines such as M112, M113, M272, M273, etc. Replacing a Mercedes-Benz serpentine is an easy task and requires about thirty minutes.

What you will need

• Mercedes-Benz Serpentine Belt
• 17mm socket
• Ratchet wrench

Procedure

1. Order the correct Mercedes-Benz serpentine belt for your car. The belt can be purchased online or at any auto parts store or dealer.

2. Park the car and allow the engine to cool down.

3. Open the hood by pulling the release under the dashboard on the driver’s side.

4. Locate the serpentine belt at the front of the engine.

5. Place a 17mm socket and ratchet on the tensioner and move the tensioner UP. Turn the wrench counterclockwise. Some models have a Hex bolt in the pulley center that can release the drive belt. Do NOT use the secure TORX bolt to release the tensioner. Use the 17mm nut below the pulley.

6. Insert a pin (such as a 6mm Allen wrench) into the locking hole. The tensioner needs to be up to insert the locking pin. Make sure that the pin is strong enough and is inserted properly. If the pin is not inserted in the proper hole or fully inserted, it can snap off and cause damage or body injuries.

7. Remove the old belt by sliding the belt away from all the pulleys.

8. Install the new belt. Route it over the power steering pump, A/C compressor, crankshaft, alternator, and idler pulley. It is important to take a picture of the old belt before removing it and using it as a reference. Otherwise, you will be wondering how to route the belt. The serpentine belt routing is printed on top of the upper radiator support or under the hood on some cars.

9. Next, slide the serpentine belt over the tensioner pulley.

10. Check that the belt is seated properly on all the pulleys. If the belt is not seated properly, it won’t be easy to slide over the tensioner, even on one pulley.

11. Use the 17mm to lift the tensioner and remove the pin.

12. Slowly lower the tensioner and allow it to load on the belt.

Notes

• No parts need to be removed to remove and replace the Mercedes serpentine belt.
• Removing the engine cover by pulling it up can make this job easier but unnecessary.
• The radiator cooling fan does not need to be removed.
• A pin can lock the tensioner in the UP (preloaded) position.
• It is possible to change the belt without using a locking pin.
• Take a picture of the belt routing before you remove the belt.
• Do not use the Secure Torx bolt to release the tensioner.
• If you have a turbo intake pipe, remove it to access the tensioner.
• The original belt can potentially last up to 100k miles. We recommend changing it every 60,000 miles.

Serpentine Belt Replacement Cost

It costs less than $50 to change the Mercedes-Benz serpentine belt yourself. The average cost to change the dealer or mechanic belt ranges between $200 and $450 for labor and parts.

Can I drive my Mercedes-Benz if the serpentine belt is broken?

It is not recommended to drive your car if the serpentine belt is broken, as it can cause several problems. The engine will usually keep running, but on these engines the water pump is driven by the belt, so the engine will overheat within minutes, and the alternator stops charging the battery. The power steering and air conditioning will also stop working. This can create unsafe driving conditions and cause additional damage to your vehicle. It is best to have the belt inspected and replaced immediately.

Applications

Instructions on how to change the Mercedes-Benz drive belt apply to the following models. These instructions may apply to other models not included in this list.

• 2001 to 2005 C240
• 1998 to 2000 C280
• 2001 to 2005 C320
• 1998 to 2000 C43 AMG
• 2005 to 2006 C55 AMG
• 2000 to 2006 CL500
• 2001 to 2002 CL55 AMG
• 2003 to 2006 CL55 AMG
• 1998 to 2005 CLK320
• 1999 to 2003 CLK430
• 2003 to 2006 CLK500
• 2001 to 2006 CLK55 AMG
• 2006 CLS500
• 2006 CLS55 AMG
• 1998 to 2004 E320
• 2005 E320 4Matic
• 2005 E320 Base
• 1998 to 2002 E430
• 2003 to 2006 E500
• 1999 to 2002 E55 AMG
• 2003 to 2006 E55 AMG
• 2002 to 2008 G500
• 2005 to 2011 G55 AMG
• 1998 to 2003 ML320
• 2003 to 2005 ML350
• 1999 to 2001 ML430
• 2002 to 2007 ML500
• 2000 to 2003 ML55 AMG
• 2006 to 2007 R500
• 2006 S350
• 2000 to 2006 S430
• 2000 to 2006 S500
• 2001 to 2002 S55 AMG
• 2003 to 2006 S55 AMG
• 1999 to 2006 SL500
• 2003 to 2008 SL55 AMG
• 2001 to 2004 SLK320
• 2005 to 2010 SLK55 AMG
• 2007-08 Dodge Sprinter Van V6 3.5L
• 2006-09 Mercedes Benz C230
• 2010 Mercedes Benz C250
• 2006-07 Mercedes Benz C280
• 2008-13 Mercedes Benz C300
• 2006-11 Mercedes Benz C350
• 2010 Mercedes Benz CL550
• 2006-09 Mercedes Benz CLK350
• 2007-09 Mercedes Benz CLK550
• 2007-11 Mercedes Benz CLS550
• 2007 Mercedes Benz E280
• 2006-11 Mercedes Benz E350
• 2010 Mercedes Benz E500
• 2007-11 Mercedes Benz E550
• 2011-13 Mercedes Benz G550
• 2007-13 Mercedes Benz GL450
• 2010-13 Mercedes Benz GLK350
• 2006-11 Mercedes Benz ML350
• 2010-11 Mercedes Benz ML550
• 2006-11 Mercedes Benz R350
• 2007-11 Mercedes Benz S550
• 2007-13 Mercedes Benz SL550
• 2006-08 Mercedes Benz SLK280
• 2010-11 Mercedes Benz SLK300

Replace the tensioner and idler pulleys at the same time

The belt itself is rarely the whole job. The automatic tensioner and the idler pulleys wear at a similar rate, and a tired tensioner will chew through a new belt or let it slip under load. Spin each pulley by hand with the belt off: any roughness, play or noise means the bearing is on its way out. Doing them together costs a little more in parts and saves repeating the whole job in a year.

Photograph the routing before removing the old belt

Take a clear picture of how the belt is routed before you release the tension, even though there is usually a diagram under the hood. On Mercedes engines with air conditioning and a supercharger or extra idlers, the diagram is often for a different configuration than the one in front of you, and a belt fitted one pulley out will squeal or shred quickly.

Check the condition of the old belt as you remove it. Even cracking across the ribs is normal age, but a glazed shiny surface suggests slipping, and chunks missing from one edge usually means a pulley is out of alignment. Fitting a new belt without fixing that alignment just repeats the failure.

If a warning light appeared alongside the belt noise, scan the car before and after the repair. A slipping belt can under drive the alternator and set voltage related codes across several modules, and a full system scan confirms those have cleared once the new belt is on.

After Installing the New Belt

• Remove the locking pin, release the tensioner slowly, and check that every rib sits in its pulley groove.
• Start the engine and watch the belt for a minute; it should run straight without wobbling or walking off a pulley.
• Turn the A/C on and turn the steering wheel lock to lock to load the belt; a squeal under load points to a weak tensioner or a glazed pulley.
• If the battery light or a temperature warning appears after the job, shut the engine off and recheck the routing.

How to Get the Right Belt

Belt length varies by engine and by year, and some cars use a different belt depending on equipment. Order by your VIN or match the part number printed on the old belt. If the old belt is gone, count the pulleys and use the routing diagram on the fan shroud sticker, if your car has one.

Frequently Asked Questions

How often should I replace the serpentine belt on a Mercedes?

Mercedes does not list a fixed mileage on most of these engines; the belt is inspected at service. Many owners replace it somewhere between 60,000 and 100,000 miles, or sooner if it shows cracks, missing chunks or glazing.

Can I drive with a squealing belt?

For a short distance, but get it checked soon. A squeal often means the belt is slipping or the tensioner is weak, and if the belt breaks you lose charging and engine cooling.

How long does the job take?

Most DIYers finish in under an hour once the routing is known. Take a photo of the old belt first; routing mistakes are the most common reason the job takes longer.

Related Guides

• Mercedes-Benz Serpentine Belt Replacement 3.0 Diesel Engine
• Mercedes-Benz ML, R, GL Class Replace Serpentine Belt

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