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Mercedes Benz Belt Tensioner Replacement
 
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Pelican Technical Article:

Mercedes Benz Belt Tensioner Replacement

Steve Vernon

Time:

3 hour3 hr

Tab:

$84

Talent:

**

Tools:

Mercedes-Benz tool #103-0040, 6mm, 8mm Hex, 13mm, 19mm socket, vice grips, 13mm wrench

Applicable Models:

Mercedes-Benz 190E (1987-93)
Mercedes-Benz 260E (1987-89)
Mercedes-Benz 300CE (1988-92)
Mercedes-Benz 300D (1987)
Mercedes-Benz 300E (1986-93)
Mercedes-Benz 300TD (1987)
Mercedes-Benz 300TE (1988-93)
Mercedes-Benz E300 (1995)

Parts Required:

New drive belt, belt tensioner

Hot Tip:

Be careful working around your radiator

Performance Gain:

All of your belt driven accessories work

Complementary Modification:

New Tensioner Shock

There are several things that will need to come off the car to replace your belt tensioner including the fan. A word of caution here before you begin: Depending on the engine and accessories on your car there can be very, very little room to work between the fan and the radiator. You will need an 8mm Hex to remove the viscous clutch on the fan, and we had to grind down a socket to make it fit. The radiator is very expensive and delicate, and can be easily damaged while working around it. If you are going to be doing other work on the car and/or are worried about damaging your radiator, I recommend you remove it first. It is not a difficult job and can potentially save you a lot of money if you end up damaging it. That being said, you certainly can replace your belt tensioner with the radiator in, but I recommend you put a piece of cardboard over it to protect it while working.

Begin by removing the thermostat overflow hose from its clip on the top of the engine, and remove the distributor cover plate. It is just held in by clips and pulls off.

Next remove the fan shroud. Unclip the circular part of the shroud from the base by removing the circular clip on the right side. Turn the shroud to the right, separating the circular part from the base and place it over the fan. Pry the two clips connecting the base of the shroud to the radiator off, and lift it from the engine compartment.

Insert Mercedes-Benz tool # 103-0040 behind the fan pulley, and seat it between the two groves on the housing. Gently spin the fan until the tool slips into the corresponding hole on the pulley. Remove the 8mm Hex bolt and fan from the engine compartment.

With the fan out of the way, locate and loosen the 19mm fixing bolt on the belt tensioner. Locate the 13mm adjusting nut between the water and power steering pumps and loosen.

With the nut loosened you can pull up on the belt and remove it.

Next you will need to remove the pulley for the power steering unit, water pump and the fan. All three are held on with 13mm bolts. The power steering and water pump will spin freely while you are trying to remove them, so you will want to wrap a shop rag or the old belt around them and use vice grips to hold the pulley in place while you unscrew the bolts. Be careful not to damage each pulley, as when the engine is running they spin at a high rate of speed and need to be in balance. You will need to use the Mercedes-Benz tool to hold the fan pulley from turning while you unbolt it.

With the pulleys off, remove the 6mm Hex bolt behind the fan pulley and next to the crank positioning sensor. Completely unscrew and remove the 19mm fix bolt from the tensioner and then the two 13mm bolts holding it to the support bracket and remove the support bracket.

Remove the 13mm bolt that holds the shock to its bracket by the front of the engine.

Now you can remove the tensioner pulley and tensioner rod from the engine. Depending on the condition and age of your engine, some tensioners will easily slide out and others may need a bit of a pry to get them loose.

Installation is the reverse of removal. Take care to make sure the belt is properly seated on all the pulley units, follows the right path and everything is torqued to specs.

Begin by removing the thermostat overflow hose from its clip on the top of the engine and pull off the distributor cover plate.
Figure 1

Begin by removing the thermostat overflow hose from its clip on the top of the engine and pull off the distributor cover plate.

This is what you will see on the right side of the engine.
Figure 2

This is what you will see on the right side of the engine. You will need to remove the clip that holds the circular shroud to the shroud base (yellow arrow). Turn the shroud right and separate it from the base, then place it back over the fan. From this angle you can see the fixing bolt (green arrow, below the radiator hose), and the adjusting nut (red arrow).

Remove the clip holding the shroud base to the radiator (red arrow) on the passenger side.
Figure 3

Remove the clip holding the shroud base to the radiator (red arrow) on the passenger side.

Remove the clip holding the shroud on the driver side (yellow arrow), pull the shroud up and out of the engine compartment.
Figure 4

Remove the clip holding the shroud on the driver side (yellow arrow), pull the shroud up and out of the engine compartment.

Place the Mercedes-Benz tool # 103-0040 (yellow arrow) in between the grooves on the housing and slowly rotate the fan until the tool engages the hole in the back of the pulley.
Figure 5

Place the Mercedes-Benz tool # 103-0040 (yellow arrow) in between the grooves on the housing and slowly rotate the fan until the tool engages the hole in the back of the pulley. Insert lower right shows what it looks like with the pulley off.

With the tool in place preventing the fan pulley from spinning you can remove the 8mm Hex bolt from the fan and remove the fan from the engine.
Figure 6

With the tool in place preventing the fan pulley from spinning you can remove the 8mm Hex bolt from the fan and remove the fan from the engine. Note: we have removed the radiator in our project car to give you a better photo of what you will be working on.

Loosen the fixing nut on the belt tensioner (yellow arrow).
Figure 7

Loosen the fixing nut on the belt tensioner (yellow arrow).

Loosen the adjusting nut (green arrow).
Figure 8

Loosen the adjusting nut (green arrow).

Pull up on the belt and remove it from the pulleys.
Figure 9

Pull up on the belt and remove it from the pulleys. Note: the radiator and hoses have been removed to give you a better photo of what you will be doing.

Remove the 13mm bolts (yellow arrow), on the coolant pump pulley and remove the pulley.
Figure 10

Remove the 13mm bolts (yellow arrow), on the coolant pump pulley and remove the pulley.

Remove the 13mm bolts on the power steering pump and remove the pulley.
Figure 11

Remove the 13mm bolts on the power steering pump and remove the pulley.

Using the Mercedes-Benz tool #103-0040 (green arrow) and a 13mm socket, remove the bolts from the fan pulley and then remove the pulley.
Figure 12

Using the Mercedes-Benz tool #103-0040 (green arrow) and a 13mm socket, remove the bolts from the fan pulley and then remove the pulley.

Next, using a 6mm Hex, remove the bolt (yellow arrow) on the end of the tensioner bracket by the crank positioning sensor.
Figure 13

Next, using a 6mm Hex, remove the bolt (yellow arrow) on the end of the tensioner bracket by the crank positioning sensor.

Remove the 19mm fix bolt from the tensioner.
Figure 14

Remove the 19mm fix bolt from the tensioner.

Remove the two 13mm bolts from the tensioner bracket (red arrows).
Figure 15

Remove the two 13mm bolts from the tensioner bracket (red arrows). TIP: One of the bolts holding the Y shaped tensioner bracket bolts onto the power steering pump actually has a nut at the back! If you don't know this, you cannot unscrew it and it will cause you major frustration/panick. Just use another ratchet to hold the nut at the back to remove the bolt.

Move to the tension shock and remove the top 13mm bolt from its bracket.
Figure 16

Move to the tension shock and remove the top 13mm bolt from its bracket. You do not need to remove the bracket or the lower bolt to remove the tensioner.

Remove the tensioner bracket from the engine.
Figure 17

Remove the tensioner bracket from the engine.

Depending on the condition and age of your car, the tensioner, shock and adjuster arm can be slipped down and out of the engine.
Figure 18

Depending on the condition and age of your car, the tensioner, shock and adjuster arm can be slipped down and out of the engine. On some cars you might need to give them a little pry, or the tensioner and adjusting rod may come out separately. You can see how the unit needs to be lowered as it comes out so the adjusting rod can clear the upper bracket (green arrow). Note: The radiator and hoses have been removed to provide a better picture of what you will be doing.

Here is a photo for the tensioner and shock (red arrow), the adjusting rod (yellow arrow) and tensioner bracket (green arrow).
Figure 19

Here is a photo for the tensioner and shock (red arrow), the adjusting rod (yellow arrow) and tensioner bracket (green arrow). Installation is the reverse of removal. Take care to make sure the belt is properly seated on all the pulleys, follows the right path and everything is torqued to specs.

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Comments and Suggestions:
Mike Comments: Question ? ....... Can the tensioner shock itself be replaced

without taking the belt and all those pulleys off. I just need

to replace the shock absorber itself. It only has the two 13mm bolts. How can i do this ?
July 22, 2016
  Followup from the Pelican Staff: You're better of removing it. Otherwise you are trying to install it with tension on the pulley, even with the belt off. - Nick at Pelican Parts  
PC Comments: I have a chain wrench that I wrap around the pulleys for removing/installing the bolts. Much easier..
May 20, 2016
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
Fixedbyme Comments: W124 280TE 1992 eng 104.942 I replaced water pump and after re-fitting pulleys. The loose belt doesn't tension up with Belt Tensioner Rod adjustment nut with locking bolt back off10mm hex. Which way does the lockplate as attached to rod - face onto the back of belt tightener? The marked triangle on belt tightener should the plastic pointer be pointing to with a loose belt or tight belt?
March 17, 2016
  Followup from the Pelican Staff: The plate should be angled toward the left side of the engine. when seated in the driver seat. See the final image for the angle. Indicator should point when tensioned. - Nick at Pelican Parts  
Ted Comments: I still can't seem to get the power steering pulley off. I've taken the 3 13mm bolts out but there seems to be something else holding it in and I cannot see what it is. What is this other bolt and how do I get it out I tried with a deep 6mm socket and that didn't work.
March 6, 2016
  Followup from the Pelican Staff: The center shaft is likely rusted or corroded to the pulley. You may have to replace the pulley once you have it off. Try levering it back and forth to remove it. - Nick at Pelican Parts  
Aperture7 Comments: One thing I have to point out is one of the bolts holding the Y shaped tensioner bracket bolts onto the power steering pump. This bolt actually has a nut at the back!!! If you don't know this, you cannot unscrew it and it will cause you major frustration/panick. Just use another ratchet to hold the nut at the back to remove the bolt.
July 25, 2015
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it. I will have the article updated.
- Nick at Pelican Parts
 
aperture7 Comments: Hi when I tried to remove the two 13mm bolts holding the Y shaped tensioner bracket, the lower bolt would rotate with the ratchet, but will not come out. What is happening here?
July 23, 2015
  Followup from the Pelican Staff: It may corroded, is it loose? try pulling it out as you loosen it. - Nick at Pelican Parts  
Macca Comments: Hi Guys... Great Info... A couple of things... Why would you not first loosen all pulley bolt before taking off the belt? And comments from Tom re tensioner replacement November 25 2014...Fig. 7: "Loosen the fixing nut reversed thread on the belt tensioner yellow arrow" Doesn't he mean Fig 8? Loosen the adjusting nut green arrow.That nut is reverse thread isn't it? Just need to get this right before I start doing this job? Thanks in advance for your reply on this... Garth 88 300sel Australia
June 5, 2015
  Followup from the Pelican Staff: The pulleys will not rotate when loosening, I believe that is why the author removes the fasteners after the belt.

I can't speak for Tom, follow the steps in the article. Maybe Tom will chime in.- Nick at Pelican Parts
 
JayB Comments: excellent guide and valuable information
May 19, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Chris Comments: Can I re use the adjusting rod? I've seen a lot of them for sale and I'm not sure if I need it. Thanks.
May 14, 2015
  Followup from the Pelican Staff: You should be fine reusing it. As long as it isn't worn out. - Nick at Pelican Parts  
hamada128 Comments: Thanks Nick. I forgot to mention it is a 1993 190E with the 2.3 engine so I have more room than the 2.6.
Another question, could the pulley only fail and cause the belt to have some slack after tightening the belt.
I followed the correct method of using the tensioner, so the tension rod is not broken.
March 5, 2015
  Followup from the Pelican Staff: You can check if the pulley is faulty by removing the belt and checking it for binding or excessive play in the bearing. - Nick at Pelican Parts  
hamada128 Comments: Can I only replace the tensioner pulley without needing to take the whole assembly out? Thanks.
March 4, 2015
  Followup from the Pelican Staff: You should be able to, as long as the fastener clears the raditor components when removing. The fastener for the pulley is removed from the front. - Nick at Pelican Parts  
tom Comments: '92 300e w75k mi.: Tensioner w pulley and belt replaced. Followed Pelican instructions; took my time; cleaned some dirt = 2 days. Radiator in. Just a couple of points: Lots of WD 40!
Mercedes-Benz tool # 103-0040. Get one. I used a long 6mm hex/allen w end clipped 1/4" and rounded. It worked but a real pain.
Removing Fan; then viscous coupling; then fan pulley: my fan to coupling w hex/allen bolts.
Removing coupling: Not a reversed thread A tough nut. I used 3/8" breaker bar w pipe extension & 8mm hex/allen socket. Important step. Pelican staff helpful here. Do not strip the allen bolt!
Fig. 7: "Loosen the fixing nut reversed thread on the belt tensioner yellow arrow" Good info and warning pic at http://www.peachparts.com/shopforum/tech-help/266215-tightening-serpentine-belt.html
Fig. 13: My '300e has a bolt, not 6mm Hex. Fig. 15: Bottom 13mm bolt has a hex nut behind tensioner that fell off in unreachable spot. I used extending wand magnet to retrieve & hold back in place for reassembly.
Reassembly has to be the reverse. Thanks again to Pelican.



November 25, 2014
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
Tom Comments: '92 300e: just noticing and hearing very loose belt. Tensioner? I removed shroud to have a look, but fan coupling is held in place with allen bolt. In fig. 6 are you saying your socket wrench is on a hex bolt/nut? Either way, it seems I'll need tool # 103-0040 to remove fan. Best info on the net here, photos are great.
October 15, 2014
  Followup from the Pelican Staff: The ratchet is being used to loosen an 8mm bolt. - Nick at Pelican Parts  
marc-fritz Comments: dear sir,i ws in a accident with my 190 e 2.3 benz,the all front been destroyed.the belt tensioner and damper are gone,and I am unable to put them back togheter.what do I need as far as assembly is concerned .a damper..a braket''roller..tensioner
October 7, 2014
  Followup from the Pelican Staff: It depends on what is broken.

Give our parts specialists a call at 1-888-280-7799, describe what is broken and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
 
magician Comments: Best site on net for this subject, period.
September 3, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
matt Comments: How do you keep the pulleys from spinning? I can't get anywhere because everything keeps spinning.
August 3, 2014
  Followup from the Pelican Staff: See steps 5 -6 . - Nick at Pelican Parts  
optimusprime Comments: Yes, and i must thank you also. Not only for this water pump fix, but other jobs i have had to do. My first call is Pelican parts .Full of good information .
June 21, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
optimusprime Comments: Very good. But if it moves retracts and returns and is smooth, the part that adjuster fits to could be in the wrong possition, when its worn dont you think. And if it was in the wrong place would it still work.
June 11, 2014
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
Mario Comments: How do you know if the tensioner needs to be replaced? Or how to check if the tensioner still good?
May 18, 2014
  Followup from the Pelican Staff: Check if the pulley is smooth and bearing lacks play. Also check that the tensioner retracts and returns smooth. - Nick at Pelican Parts  
jesse Comments: your illusrations for the removeal of the fan belt tensioner and associated parts was pretty good and helpful. i was wondering how many hours it would take to complete such a task for a certified mechanic? thank you. i was told approximately 3 hrs.
November 11, 2013
  Followup from the Pelican Staff: It could take around 3 hours. Depending on the condition of the vehicle and how easy everything comes off and goes back together. - Nick at Pelican Parts  
George Comments: Just wanted to thank you for this great tutorial. Really helped on this job.
August 4, 2013
  Followup from the Pelican Staff: Thanks, and remember we're here to help - Kerry at Pelican Parts  

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