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Timing Chain Tensioner Replacement
 
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Pelican Technical Article:

Timing Chain Tensioner Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$65

Talent:

**

Tools:

10mm Allen, 27mm, 13mm socket

Applicable Models:

Mercedes-Benz W124 (1986-95)

Parts Required:

Timing Chain Tensioner

Hot Tip:

Watch your knuckles it is in a tight spot

Performance Gain:

Correct tension on the timing chain

Complementary Modification:

Change drive belt

The timing chain tensioner is located on the front right side of the engine block. It is a tight space to work in but if you feel comfortable it is possible to replace without removing a lot of other parts.

You will need to remove the drive belt. Please see our article on drive belt replacement for additional assistance. You may also find that you would like more room to work by removing the fan, shroud and air filter box; if that is the case please see our article on all of these procedures for additional instruction.

The tensioner is oil pressure fed and once removed from the motor must be reinstalled in a very particular order. Never just remove it and stick it back in, you may end up with the improper tension on the chain which can lead to catastrophic damage to the motor.

The timing chain tensioner is located on the front right side of the engine block (red arrow).
Figure 1

The timing chain tensioner is located on the front right side of the engine block (red arrow).

This photo illustrates where the tensioners thrust pin makes contact with the chain rail and holds it in position (yellow arrow).
Figure 2

This photo illustrates where the tensioners thrust pin makes contact with the chain rail and holds it in position (yellow arrow). Note the chain housing cover is off only for illustration purposes; you do NOT need to remove it. You will need to swing the air pump out of the way to get access to the tensioner (green arrow). Loosen the lower 13mm bolt and remove the top one (red arrow) on the air pump and then swing it out of the way with the hoses and lines attached. Place a cloth or rag over the pump and alternator to prevent oil from the tensioner getting in the units.

Use a 10mm Allen and loosen the inner screw plug (red arrow) one complete turn.
Figure 3

Use a 10mm Allen and loosen the inner screw plug (red arrow) one complete turn.

Next remove the 27mm tensioner housing with a socket (red arrow).
Figure 4

Next remove the 27mm tensioner housing with a socket (red arrow).

Completely unscrew the housing and remove the tensioner and housing as one unit (red arrow).
Figure 5

Completely unscrew the housing and remove the tensioner and housing as one unit (red arrow).

Take the tensioner to your bench and place it on a clean soft surface.
Figure 6

Take the tensioner to your bench and place it on a clean soft surface. Fully remove the inner screw plug (red arrow) and then push the thrust pin back out through the housing (yellow arrow). 

After cleaning and checking the condition of the tensioner you must reinstall everything in a particular order.
Figure 7

After cleaning and checking the condition of the tensioner you must reinstall everything in a particular order. Begin by installing a new washer (yellow arrow) and the tensioner housing (red arrow) back into the engine and torqueing to spec.

Next install the thrust pin (yellow arrow) and detent spring or clip (red arrow) into the tensioner housing.
Figure 8

Next install the thrust pin (yellow arrow) and detent spring or clip (red arrow) into the tensioner housing. Then install the spring (green arrow).

Install the filler pin (yellow arrow) a new seal (red arrow) and the screw plug (green arrow) and torque to spec.
Figure 9

Install the filler pin (yellow arrow) a new seal (red arrow) and the screw plug (green arrow) and torque to spec. Installation of the rest is the reversal of removal. After everything is back together start the motor and check for oil leaks.

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Comments and Suggestions:
leon Comments: I seem to get no answers for my question namely:- hoe to replace a timing chain on a 1993 230 E m/benz 124motor
August 28, 2016
  Followup from the Pelican Staff: Got it, thanks. - Nick at Pelican Parts  
Leon Comments: I would like to know how to change the timing chain
August 28, 2016
  Followup from the Pelican Staff: We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

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
 
BJ Comments: You can also tell if the timing chain tensioner needs to be replace by pulling up on the chain to see if the chain is loose on the chain sprockets or if there is any slack on the chain.
February 14, 2016
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
quest1966 Comments: Understanding that the tensioner is oil pressure fed, if the tensioner is shot, it backs off on the passenger side guide rail allowing the chain the clang loosely on the bottom of the guide. Is that about right? Thank you!
June 16, 2015
  Followup from the Pelican Staff: The chain would loose all the way around, timing would be slightly off due to this. - Nick at Pelican Parts  
quest1966 Comments: Vehicle: w-124, engine: 104.992. I don't believe the timing chain is making noise. Can you describe at all what I should listen for? Thank you for all of your replies, Nick!
June 12, 2015
  Followup from the Pelican Staff: The timing chain would rattle, would emanate from behind the timing cover. - Nick at Pelican Parts  
quest1966 Comments: How can I tell if the timing chain tensioner needs to be replaced? Thank you.
June 11, 2015
  Followup from the Pelican Staff: What vehicle? generally: If you have good oil pressure, and timing chain noise. - Nick at Pelican Parts  

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