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Replacing the Timing Chain Camshaft Sprocket
 
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Pelican Technical Article:

Replacing the Timing Chain Camshaft Sprocket

Mike Holloway

Time:

30 minutes30 mins

Tab:

$50 to $350

Talent:

**

Tools:

22mm socket wrench, large flathead screwdriver, needle nose pliers, breaker bar (optional), torque wrench

Applicable Models:

Mercedes-Benz R107 (1972-89)

Parts Required:

Timing chain camshaft sprocket

Hot Tip:

Use a clean rag to protect chain and engine compartment

Performance Gain:

Proper chain tension and increased wear resistance

Complementary Modification:

Timing chain, chain guide, chain tensioner replacement

One would think that when the engine is at speed there is a higher incidence of wear and eventual failure. This isn't necessarily true in the case of certain components, namely the timing chain. Chains, sprockets, gears and even bearings experience the most wear upon startup. The timing chain and the various components (guide rails, tensioning rail, chain tensioner) wear out after 100,000 miles and should be replaced. The sprockets should also be replaced. The chains can stretch but they also wear. As each rolling element of the link begins to experience wear it sets up for increased vibration and movement of the chain links and pins against the sprocket surface. As many teeth as the sprocket has, the chain has many more links. The sprocket surface wears down contributing to sloppy movement as the chain passes over the sprocket surfaces. This creates an even greater opportunity for chain breakage.

The guide rails will be the first order of business to address. In order to change the guide rails in preparation for the replacement of the timing chain, all the components in front will have to be removed. This includes the belts, pulleys, alternator, the distributor and the power steering pump were all removed. Please refer to these articles should you need edification.

I also removed the radiator. Normally you wouldn't have to do that but it was already out due to the development of another article. Refer to removing the radiator article for help in that regard.

Also, the distributor should be set at top dead center (TDC) and marked. This is needed when you put everything back. The distributor was also removed earlier. Hence, you can refer to distributor removal article if you need assistance.

The valve cover will have to be removed as well. In order to do that you will have to remove the air box. Refer to the valve cover removal article for help on how to do that project.

After the chain guide rails and the chain tensioner have been removed, the timing chain sprocket on the camshaft can now be removed. The crankcase sprocket will be removed later.

Before you do any work on your car it is important that you wear safety glasses, work gloves and dispose of all fluids in a safe manner.  Coolant is poisonous and should be treated as such.  Animals and small children have been known to die from ingesting coolant.  If you have to jack up your car, make sure to use jack stands and chock your wheels as well as applying the parking brake. Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never 

Use a large flathead screwdriver to keep the sprocket in place.
Figure 1

Use a large flathead screwdriver to keep the sprocket in place. Using a 22mm socket wrench, loosen and remove the bolt holding the sprocket in place.

be sure not to drop the washer into the engine.
Figure 2

be sure not to drop the washer into the engine. 

Place a clean rag over the covering in order to protect the engine from debris falling in.
Figure 3

Place a clean rag over the covering in order to protect the engine from debris falling in. Remove the sprocket and keep the chain secured with the rag and a screwdriver.

The sprocket is now free and can be replaced.
Figure 4

The sprocket is now free and can be replaced. Installation is the opposite of removal. 



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Comments and Suggestions:
Jim Comments: I was able to replace both sprockets without taking the guide rails or the chain off. It was quite easy. I did not have to remove the alternator but did have to remove the power steering pump in order to tap the new sprocket back on for the driver's side sprocket. I also removed the chain tentioner to replace it with a new one, but could have changed the sprockets without doing so. Next time in another 100000 I'll replace sprockets, chain, guide rails, and tensioner all at one time.
April 5, 2016
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Jim Comments: Can you take the sprocket off without taking the guide rails out? A PO had the chain and guide rails replaced 2000 miles ago but did not replace the sprockets or the tensioner. I have the tensioner out. I'm also installing a 2 degree woodruff key on the passenger side camshaft. Actually, the sprockets look good, but I really don't know how to judge their wear. Would appreciate any thoughts.
Jim Bianchi
March 3, 2016
  Followup from the Pelican Staff: You may be able to unbolt it, however it will be difficult to get on and off. Follow the steps in the article for replacing the sprocket. - Nick at Pelican Parts  

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Page last updated: Fri 12/2/2016 02:46:01 AM