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Timing Chain Tensioner Replacement
 
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Pelican Technical Article:

Timing Chain Tensioner Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$6

Talent:

**

Tools:

19mm socket, 13mm wrench

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Timing chain

Hot Tip:

You need a friend to help

Performance Gain:

Proper tension on chain

Complementary Modification:

Valve adjustment

If your motor has over 100,000 miles on it and is still running the original tensioner spring, you should consider replacing it. Increased noise from the chain and sprocket area is a good sign that the spring is starting to fail. While the springs very seldom catastrophically fail, they can rub against the inside of the housing and they do compress and loose tension over the years. If the spring loses enough tension it can allow the chain to jump a sprocket and this can result in catastrophic engine damage.

Changing out the spring is not hard and depending on which model you have, you may have to move different components out of the way. This spring replacement was performed on a late model 300TD.

Over the years your car may have been serviced by multiple people including previous owners and this can lead to parts replaced with different size fasteners and hardware. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches. If something is different on your vehicle please let us know and share your info to help other users. If you have any questions or comments or even a different procedure you would like to share please leave it below and please leave your vehicle information.

The tensioner and spring are located on the front right side of the motor under the EGR valve (red arrow).
Figure 1

The tensioner and spring are located on the front right side of the motor under the EGR valve (red arrow).

Remove the air intake pipe (red arrow) to give you room to access the tensioner.
Figure 2

Remove the air intake pipe (red arrow) to give you room to access the tensioner.

Remove the EGR tube using a 13mm wrench and remove the A/C bracket attached to the thermostat (yellow arrow).
Figure 3

Remove the EGR tube using a 13mm wrench and remove the A/C bracket attached to the thermostat (yellow arrow).

While you do not need to remove all of the components in this picture, this is what the 19mm chain tensioner bolt looks like (red arrow).
Figure 4

While you do not need to remove all of the components in this picture, this is what the 19mm chain tensioner bolt looks like (red arrow).

Use a 19mm socket and remove the bolt (red arrow).
Figure 5

Use a 19mm socket and remove the bolt (red arrow). Even though the spring is not under a lot of tension make sure not to lose the bolt, washer or spring when removing.

Always replace the crush washer when changing the spring.
Figure 6

Always replace the crush washer when changing the spring.

You can see in the photo how much the old spring has compressed over the years.
Figure 7

You can see in the photo how much the old spring has compressed over the years. Installation is the reverse of removal.

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Comments and Suggestions:
Charlie Comments: Hello my name is Charlie. I have a perfect 300d and the head gasket is leaking antifreeze to exhaust.. what parts in total would you order to start to replace the head gasket?????
March 3, 2017
  Followup from the Pelican Staff: There should be a head gasket kit available with everything you need. 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
 

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Page last updated: Sun 8/20/2017 03:10:27 AM