Mercedes-Benz Parts Catalog Mercedes-Benz Accessories Catalog Mercedes-Benz Technical Articles Mercedes-Benz Tech Forums
 
Follow Pelican Parts on Facebook Follow Pelican Parts on Twitter Follow Pelican Parts on Instagram Follow Pelican Parts on YouTube Follow Pelican Parts on Pinterest Follow Pelican Parts on Tumblr
  Search our site:    
View Recent Cars  |   Cart  | Project List | Order Status | Help    
 >  >
Mercedes Idler Pulley Replacement
 
Bookmark and Share

Pelican Technical Article:

Mercedes Idler Pulley Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$15

Talent:

*

Tools:

E10, E50 Torx driver, flathead screwdriver

Applicable Models:

Mercedes-Benz ML320 (1998-03)
Mercedes-Benz W203 (2001-07)

Parts Required:

New drive belt

Hot Tip:

Lock the tensioner

Performance Gain:

Quiet Engine

Complementary Modification:

New tensioner

The idle pulley sits directly above the coolant pump pulley 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 V-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.

Replacing the idle pulley on your Mercedes-Benz W203 is one of the easiest jobs you will do. You should be able to do it in less than 30 minutes and is a great starter project if you are just beginning to DIY or "Do It Yourself" on your car.

You will need to remove the belt to replace the idle pulley. Let the car cool so you don't have to work around a hot engine. Locate the tensioner and using an E10 Torx driver turn it counter-clockwise 45 degrees. You can now slip the belt off the tensioner.

You can also lock the tensioner into the open position if you need both hands to install the new belt. Turn the tensioner all the way counter-clockwise and insert a retaining pin between the rotating part and the tensioner base. If you do not have a retaining pin you can use a 5mm Allen key.

With the belt off insert a flathead screwdriver between the cover plate and the idle pulley and gently pry the plate off. With the plate off use a T-50 Torx and remove the pulley bolt. The bolt is extra long so make sure to label it as it is not easy to replace if you loose it. Make sure you clean any debris from the mounting surface of the pulley before installing the new one.

Installation is the reverse of removal. Make sure the belt is properly seated on all the pulleys and that it follows the right path.

You are going to remove the Poly-V belt to remove the idle pulley (yellow arrow).
Figure 1

You are going to remove the Poly-V belt to remove the idle pulley (yellow arrow). This picture illustrates the routing of the belt for reference when it is time to reinstall it. The red arrow shows the belt tensioner. Note: most of the front of the car has been removed to better illustrate the procedures, you do not have to remove anything other than what is listed in the article.

Locate the tensioner and using the Torx driver turn it counter-clockwise 45 degrees.
Figure 2

Locate the tensioner and using the Torx driver turn it counter-clockwise 45 degrees. You can now slip the belt off the tensioner and install the new one.

You can also lock the tensioner into the open position if you need both hands to install the new belt.
Figure 3

You can also lock the tensioner into the open position if you need both hands to install the new belt. Turn the tensioner all the way counter-clockwise and insert a retaining pin between the rotating part and the tensioner base. If you do not have a retaining pin you can use a 5mm Allen bolt.

Located the idle pulley right above the coolant pump pulley.
Figure 4

Located the idle pulley right above the coolant pump pulley. Insert a flathead screwdriver (red arrow) between the cover plate and the pulley and gently pry the plate off.

With the plate off use a T-50 Torx (red arrow) and remove the pulley bolt.
Figure 5

With the plate off use a T-50 Torx (red arrow) and remove the pulley bolt.

The bolt (red arrow) is extra long so make sure to label it as it is not easy to replace if you loose it.
Figure 6

The bolt (red arrow) is extra long so make sure to label it as it is not easy to replace if you loose it. Make sure you clean any debris from the mounting surface of the pulley before installing the new one.

Bookmark and Share
Comments and Suggestions:
21C Comments: Thank you guys for the information...It was a water pump failure...thanks again!
August 9, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
21C Comments: My serpentine belt came off, antifreeze/coolant started leaking and it look like the belt tension pulley is damaged what am i to do? 98 E320 w210 4matic wagon
July 18, 2016
  Followup from the Pelican Staff: Sounds like the water pump failed.

Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Celander Comments: Hi Thanks for your very good DIY "Mercedes Idler Pulley Replacement" , I did it, No Problems :o

Have a nice day!

Cheers

Robert Celander
Sweden
April 9, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help. - Nick at Pelican Parts  
Bob Comments: should you remove the fan before attempting to replace idler
pulley
March 7, 2015
  Followup from the Pelican Staff: Yes, if your vehicle is equipped with one. - Nick at Pelican Parts  
Pepper Comments: How tightly do you torque the bolt on the re-install?
January 7, 2015
  Followup from the Pelican Staff: I don't currently have that spec.
I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 

  Search our site:    

View Cart & CheckOut | Project List | Order Status |  Help    

 

[Home] [Customer Service] [Shopping Cart] [Project/Wish List]
  [Privacy Statement]  [Contact Us] [About Us] [Shipping] [Careers]

Copyright © Pelican Parts Inc. -    DMCA Registered Agent Contact Page

Page last updated: Fri 12/9/2016 02:29:27 AM