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Pelican Technical Article:

Serpentine Belt Tensioner Replacement

Jared Fenton

Time:

1 hour1 hr

Tab:

$55

Talent:

****

Tools:

13mm socket, T40 Torx driver

Applicable Models:

Jetta MkIV 2.0L (1998-05)

Parts Required:

Serpentine belt tensioner

Hot Tip:

Check the belt pulley for wear or noise

Performance Gain:

Assurance you won't lose tension

Complementary Modification:

Replace serpentine belt

The VW Jetta 2.0 uses a serpentine belt to drive the various ancillary components on the engine. This includes the alternator, A/C compressor, and the power steering pump. The serpentine belt is kept in place by a spring mounted to a bracket with an idler pulley. This is called a belt tensioner. Over time, the serpentine belt can stretch. The tensioner setup is designed to allow a certain amount of flex to account for stretching as well as vibration.

Over time, the spring that holds tension on the belt can wear out, causing less tension to be applied to the serpentine belt. Additionally, the bearings in the idler pulley can also begin to fail causing noise. If you ignore a bad bearing long enough, the pulley can lock up and snap the belt.

To inspect and/or replace the tensioner, first remove the serpentine belt from the engine. Please see our article on Serpentine Belt Replacement for more information.

Once the serpentine belt is removed, you'll want to spin the pulley and check that it moves freely with no noise or side-to-side play. If the pulley is binding, makes noise, or the contact surface is damaged, you'll want to replace it. Grooves worn into the surface of the pulley from the belt is also a sign that it should be replaced.

You'll also want to check the tension on the tensioner spring. Typically, it should take a good amount of force to relieve tension on the belt. If it is easy to compress the tensioner and you hear a good amount of belt squeal when running, think about replacing the tensioner.

Shown here is a diagram of the serpentine belt routing on the VW 2.
Figure 1

Shown here is a diagram of the serpentine belt routing on the VW 2.0 engine. The belt tensioner presses down on the belt, keeping it tight. This tension allows the belt to drive the other components. When the tensioner starts to fail, it cannot hold as much tension on the belt, causing it to slip on the other pulleys and make noise.

Once the serpentine belt has been removed, loosen and remove the three 13mm bolts (green arrows) holding the tensioner to the engine.
Figure 2

Once the serpentine belt has been removed, loosen and remove the three 13mm bolts (green arrows) holding the tensioner to the engine. Slide the tensioner out from under the bracket. Note: the alternator has been removed to provide clarity in this picture.

Once the tensioner has been removed, inspect the pulley for wear.
Figure 3

Once the tensioner has been removed, inspect the pulley for wear. These grooves (green arrow) worn into the pulley are a sign that the pulley should be replaced. Spin the pulley as well. If it makes any noise or if resistance is felt, replace the pulley.

If you are just replacing the pulley, Loosen and remove the T40 Torx screw (green arrow) holding the pulley onto the tensioner.
Figure 4

If you are just replacing the pulley, Loosen and remove the T40 Torx screw (green arrow) holding the pulley onto the tensioner. Remove the old pulley and install the new one in its place.

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Comments and Suggestions:
DarkSim905 Comments: I really love these technical articles. The only suggestion I have is add a general guideline as to when these tasks should be performed, assuming a new vehicle or if it's never been done before. I the guideline I've always been given was ~100,000 miles. I had mine done recently at 115k miles :
August 15, 2015
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 

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