Code for timing chain!
 

If I am looking at the Service Record in the service handbook in the glove compartment is there anyway to tell if the timing chain has been replaced?

Does the MB Dealer use a code such as 101 Service to indicate a chain replacement?

Timing chain replacement is not a maintenance job so it will not show on any normal service records. Service repair histories are only kept by the individual dealer (I think).

I am not familiar with 101 service but any job operation that refered to the timing chain would begin with the group designation 05.

The important service info on your timing chain is the color of the top chain rails. The life of the chain is relatively unimportant. My recommendations are to replace the rails every 75k miles and the chain every 150k (but that is only for ultimate security as the rails are the problem). BTW the lower right rail will need to be replaced every 250k to achieve the same security (as they wear through at around 300k).

Steve,

Do you think an '88 420SEL's guides should be changed due to its age, even though it has under 50k miles on it?

The guides are a copper alloy and are only used up through wear not age (they are not likely to corrode). The guides are easily checked for wear with the cylinder head off. If the head is on then don't worry about the guides .... replace the seals from the outside, till they don't work any more. Unless the guides are moving the new seals will fix the problem of oil consumption ... always (at least as always as can ever be stated)

Steve:

Sorry, but I was refering to the timing chain guides - My car is 14 years old with 49k on it, and the 4.2L engine is notorious for timing chain failures due to broken chain guides.

Sorry,

Yes, the plastic chain rails definitly are age sensitive. They turn hard and brittle over time and exposure to hydrocarbon vapors (my own interpretation). Mileage and heat cycles and oil changes also matter. But age does them in.

An experienced MB tech can tell how "well done" they are by looking at the color. Anything beyond soft amber scares me. They are semi-translucent white to start with.

The brand new chain guides I put in were a medium dark amber.