|Change chain when it rattles
Question : I RECENTLY bought a used 1997 Mercedes Benz E280. Although
the vehicle is now approaching nine years old, it has only done 25,000km. I
have been advised that the timing chain requires regular maintenance and I
wonder at what mileage or time interval should the chain be replaced.
Answer : THE valve timing mechanism of a modern vehicle is
usually driven by a chain or a toothed rubber belt.
Gears are also used although these are uncommon
except on some heavy-duty diesels.
The timing belt, as it is often called, is the most
common choice. It is cheap, light and, more importantly, silent in operation.
However, the disadvantage of the rubber belt is that
it requires periodic tensioning and renewal, failing
which it can break and cause extensive damage to
The cost of labor to remove and refit is often higher than the price of the replacement belt itself.
The recommended renewal interval for a timing
belt ranges from 50,000km to 100,000km, and varies
from one engine manufacturer to another.
The timing chain is more robust and seldom
requires any attention during the life of the engine. No
regular maintenance or renewal is scheduled for timing chains although, occasionally, the automatic chain
adjuster (or tensioner) may require renewal if it is
excessively worn. However, this usually happens only
after extremely high mileages when the engine will
have to be dismantled anyway for other components
to be replaced.
A worn chain or adjuster soon becomes obvious, the
tell-tale symptoms being a loud rattling noise each
time the engine is accelerated. Timing chains are not
expensive to purchase, often not much more than a