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Belt Tensioner Replacement
 
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Pelican Technical Article:

Belt Tensioner Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$80 to $200

Talent:

**

Tools:

E12 Torx driver, 4mm Allen or drill bit

Applicable Models:

Mercedes-Benz C350 (2008-15)
Mercedes-Benz GLK350 (2010-15)

Parts Required:

Belt tensioner

Hot Tip:

Don't work on a hot engine

Performance Gain:

Will not leave you stranded at the side of the road

The V-belt or drive belt tensioner provides a constant tension on the belt that is needed to run all of the engine accessories. Over time the tensioner can fail to maintain the proper tension, and the belt will start to slip. If this happens it will usually make a squealing noise. The tensioner can also fail from the bearing wearing out; this will cause the belt to wear unevenly and fray along the edges. You should check your tensioner and V-belt every six months for wear, cracking, fraying, delaminating and drying out. If the tensioner is loose or you can wiggle it or if your belt shows any of these signs you should replace them. I recommend you always replacing the belt when replacing the tensioner and recommend you buy two belts and always keep an extra one in the car. You don't want to be stranded on the side of the road for the lack of a spare drive belt.

Replacing the belt tensioner on your Mercedes-Benz W204 is a relatively easy job. You should be able to do it in an hour. It is a great starter project if you are just beginning to DIY or "Do It Yourself" on your car.

Let the car cool so you don't have to work around a hot engine.

This photo illustrates the path of the belt; you can see where it passes the alternator (red arrow), power steering pump (green arrow) and A/C compressor.
Figure 1

This photo illustrates the path of the belt; you can see where it passes the alternator (red arrow), power steering pump (green arrow) and A/C compressor. Use this illustration when installing the new belt.

You will need to remove the Poly-V or drive belt (red arrow) before replacing the tensioner.
Figure 2

You will need to remove the Poly-V or drive belt (red arrow) before replacing the tensioner. Please see our article on drive belt replacement for additional assistance.

Lock the tensioner into the un-tensioned position by turning the 17mm spud all the way counter clockwise and inserting a small 4mm Allen or drill bit into the locking hole (red arrow).
Figure 3

Lock the tensioner into the un-tensioned position by turning the 17mm spud all the way counter clockwise and inserting a small 4mm Allen or drill bit into the locking hole (red arrow).

You are going to be working with E-Torx bolts.
Figure 4

You are going to be working with E-Torx bolts. Make sure you have the right sockets and E-Torx sockets, and do not try and remove the hardware with something else.

With the tensioner locked in the open position you can get access to the two E12 bolts (red arrows) that hold the tensioner in place.
Figure 5

With the tensioner locked in the open position you can get access to the two E12 bolts (red arrows) that hold the tensioner in place. Use an E12 socket to remove the bolts and tensioner.

Before installing the new tensioner give the area behind it a good cleaning (red arrow).
Figure 6

Before installing the new tensioner give the area behind it a good cleaning (red arrow).

Here is a photo of the tensioner out of the vehicle.
Figure 7

Here is a photo of the tensioner out of the vehicle. You can see the 17mm spud for rotating the tensioner (red arrow) along with the locking pin (yellow arrow). You need to install the tensioner in the locked position. Remove the pin after you have installed the new belt. Installation is the reverse of removal. Take care to make sure the belt is properly seated on all the pulleys and follows the right path as shown in picture 1.


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Page last updated: Tue 2/21/2017 02:55:49 AM