Timing Chain

I just had the timing chain on my 1988, 420SEL, V8, 4.2 liter, 116 engine (75K miles). The work was done at a Mercedes dealership. The chain and chain tensioner were replaced but no rails as I had expected. I understood that it was an imperative that the rails be replaced but the service consultant said the rails showed no wear and needn't be replaced. Have I misread the need for rail replacement? Am I facing a rail failure and subsequent chain breakage? Or, am I just a worry wort?

I just had the timing chain and upper rails replaced on my 420. I believe that the common rule of thought here is that the rails turn amber color from heat and age, become brittle and then break, resulting in major engine repairs.

From what I can glean, the rails are not that more expensive a part and would make sense to replace while the shop is in replacing the chain and tensioner.

The lower guide rails are more difficult and may not be replaced in some instances if not needed.

My rails, at 102000 miles were amber and one was cracked, so it definitely was due.

Thanks for the advice. I wish I had asked, specifically, that the rails be replaced. I'm extremely disappointed that a MB dealership service center would not do a complete job on such an important component. I would think that MB would have a service bulletin out on rail replacement (as well as all other components of the timing chain package). I would sure like to get a hold of MB's service bulletin on the chain and related components to show to the service consultant. I should have been suspecious because of the cost. The job was done for $750. The same job was quoted at two other MB dealers at around $1,100 to $1,200. I did point out to the consultant that I had read numerous referenced from credible sources that the rails as well as the chain and tensioner shoulc be replaced. He said their experience was that the rails are not a problem if they don't show wear.

How many hours of labor did the MB dealer charge you for, for the chain and tensioner? I have been getting very different quotes - since you actually got the work done, I would appreciate your response.

Rags

Here's the break down on costs: Labor $517.50, parts $218.50. Total cost $736. The service constultant said their labor rate is $75/hr. At the rate it took just under 7 hours. ******** in Dallas told me they could do the job in five hours but I didn't get a dollar quote. I should have but a picked the closest dealer. Dallas is two hours from here. Classic Mercedes in Tyler, Tx, is one hour from here. I did get a quote from Parkplace Mercedes in Dallas: $1,100 to $1,200. They said they need the car two days. I don't know whether that included rails but I assume it did because they made a point of saying that the rail replacement was critical. In hind sight, I probably should have had the job done there.

Hope this helps. -- Jerry