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Pelican Technical Article:

Idler Pulley Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$30 to $60

Talent:

**

Tools:

T40 Torx, 15mm socket

Applicable Models:

Mercedes-Benz 300CE (1990-93)
Mercedes-Benz 300E (1990-93)
Mercedes-Benz 300TE (1989-92)
Mercedes-Benz E320 (1994-95)

Parts Required:

New idler pulley

Hot Tip:

Don't get your fingers pinched between the belt and pulleys

Performance Gain:

Quiet engine

The idle pulley is the smaller pulley on the top right side of the motor and is a high tension stress point in the belt system on your car. It can fail over time and usually will let you know it is going bad by starting to make a whining sound. If the pulley starts whining you should replace it right away as it will only get worse and then fail completely. While you are performing this work you should also check your drive belt for wear, cracking, fraying, delaminating and drying out. If your belt shows any of these signs you should replace it. I 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.

You will need to remove the fan shroud and release the tension on the belt to replace the idler pulley. You do not need to remove the fan, just move it so you have enough space to work between the blades.

To remove the idler pulley (red arrow) you will need to remove the fan shroud.
Figure 1

To remove the idler pulley (red arrow) you will need to remove the fan shroud. The shroud is made up of two parts -- the fan guard (yellow arrow) and the shroud (green arrow).

Squeeze in the tab that holds the radiator overflow hose and slide it back out of the clip on the shroud and fan guard (red arrow).
Figure 2

Squeeze in the tab that holds the radiator overflow hose and slide it back out of the clip on the shroud and fan guard (red arrow). Set the hose and clip aside.

Slide the fan guard to the right (yellow arrow, when facing the guard).
Figure 3

Slide the fan guard to the right (yellow arrow, when facing the guard). Rotating the guard will free it from its retainers. When reinstalling make sure you install the guard with the "top" marking facing up (red arrow).

With the guard free from the shroud place the guard over the fan (red arrow).
Figure 4

With the guard free from the shroud place the guard over the fan (red arrow).

Remove the clip (red arrow) that holds the shroud to the radiator on the top right hand side.
Figure 5

Remove the clip (red arrow) that holds the shroud to the radiator on the top right hand side.

Remove the clip that holds the shroud to the radiator on the left side.
Figure 6

Remove the clip that holds the shroud to the radiator on the left side. The clip is located between the two hoses (red arrow).

Using care, slide the shroud out between the fan and the radiator (red arrow).
Figure 7

Using care, slide the shroud out between the fan and the radiator (red arrow).

Slide the guard off the fan and remove it between the fan and radiator (red arrow).
Figure 8

Slide the guard off the fan and remove it between the fan and radiator (red arrow).

This photo illustrates how the plastic pegs on the guard (yellow arrows) sit in the corresponding receptacles (red arrows).
Figure 9

This photo illustrates how the plastic pegs on the guard (yellow arrows) sit in the corresponding receptacles (red arrows).

At this point you can release the tension on the belt and slip it off of the alternator pulley.
Figure 10

At this point you can release the tension on the belt and slip it off of the alternator pulley. Place a 15mm socket over the bolt on the tensioner (red arrow) and loosen the bolt to remove the tension from the belt. Slip the belt off the pulleys while you have the tension off.

Some of the idler pulleys will have covers on them.
Figure 11

Some of the idler pulleys will have covers on them. If yours has a plastic cover just pry it off and then use a T40 Torx to unscrew the pulley.

Things to check on the pulley are the bearing (yellow arrow) and the bolt.
Figure 12

Things to check on the pulley are the bearing (yellow arrow) and the bolt. There should be no lateral movement or free play in the bearing. If the bearing is really bad there may also be damage to the bolt (red arrow).

Check that the bearing mounting surface is clean and level.
Figure 13

Check that the bearing mounting surface is clean and level. If the idler pulley was really bad there may be some damage to the mounting surface and there is no point installing a new pulley on an uneven surface as the pulley will begin to wobble and destroy itself in short order. Installation is the reverse of removal.


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Comments and Suggestions:
Ray Comments: Hi everyone, i have a 1995 mercedes E320 the 124 body type with the M104 engine i'm trying to remove the fan clutch since the fan-clutch puley-bearing is bad. I've tried but it seems that i need some sort of tool to hold the puley before i'll be able to remove the center bolt. can anyone help. i've already bought the bearing-bracket, puley and fan clutch, but i just cannot get it off.
October 2, 2015
  Followup from the Pelican Staff: MB too # 104 589 00 01 00 Is used to hold it. - Nick at Pelican Parts  
arnold Comments: the illustration is clear and simple ,love it
February 20, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 

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