Certain engines with overhead camshafts have timing belts that have a limited life
span. Car makers use these belts instead of more durable chains because chains are noisier and
cost more to manufacture. Your vehicle owner's manual will recommend at
what mileage the timing belt must be replaced. These intervals range from
every 60,000 miles to every 105,000 miles. To see what is recommended for
your engine, click on the link at the bottom of this article.
The job of the timing belt is to turn the camshaft(s) at exactly 1/2 the
speed of the crankshaft while maintaining a precise alignment. This means that the crankshaft will make two
revolutions for every revolution of the camshaft. Engines will have at
least one camshaft, or as many as four camshafts in some of the V-type
engines. The camshaft causes the intake and exhaust valves to open and close
in time with the pistons which move up and down in the
cylinders. The valves must open and close at exactly the right time in
relationship to the piston movement in order for the engine to run properly.
For more information on how this works, go to "A Short
Course on Engines"
(Article Continues below)
There are two types of engines that use timing belts. They are
described as: "Interference Engines" and "Non-interference Engines" The
difference lies in the proximity between the valves and the pistons. On an
interference engine, if the timing belt slips even one notch, the piston can
crash into an open valve causing serious engine damage by bending valves and
breaking pistons. Non-interference engines will usually not self destruct,
but in either case if the belt fails, the engine will immediately shut down leaving you
stranded. The link at the bottom of this article will tell you which
category your engine falls under.
Timing belts fail without warning and on some vehicles, are almost as hard to
check as they are to change. In most cases, your only protection is to
change the belt at the recommended intervals. Timing belt replacement is not a
cheap job but it is far less costly than the alternative.
Some technicians may recommend that you replace the water pump during a
timing belt job even if there is nothing wrong with it. This is because
90% of the labor to change the water pump has already been done with the timing
belt job and some technicians consider it good insurance to replace the pump at
this time. My feeling is that some water pumps can last the life of the
car but many do fail and will cost big money to replace at a later date.
So ask your technician what his experience is with the water pump on your model
car and look at how long you plan to keep the car. This way, at least you will
be making an informed roll of the dice.
Notice: The information on this site is
not intended as a substitute for the advice of a professional who is
qualified to examine, diagnose and repair your vehicle.
Certain engines with overhead camshafts have timing belts that have a limited life
span. Car makers use these belts instead of more durable chains because chains are noisier and
cost more to manufacture. Your vehicle owner's manual will recommend at
what mileage the timing belt must be replaced. These intervals range from
every 60,000 miles to every 105,000 miles. To see what is recommended for
your engine, click on the link at the bottom of this article.