What Is a Timing Belt? 

When you look under the hood of your Audi, you'll see a belt that drives components like the air conditioning compressor and power steering pump. This is not the timing belt - it's known as the serpentine belt, and it serves a completely different purpose. 

The timing belt is what connects the engine's camshaft to the crankshaft. In other words, it's what synchronizes the opening and closing of valves during normal running conditions. Many engines still use a timing chain (not unlike a looped bicycle chain) driving sprockets; timing chains normally last the entire life cycle of the vehicle and do not need to be changed or serviced. 

Timing belts, however, are a toothed rubber belt concealed behind a cover and not serviceable without disassembly. As you can probably guess, this rubber belt will stretch and eventually fail over time. 

What Happens If the Timing Belt Fails? 

When the belt fails, the valves are no longer in sync with the pistons, meaning the pistons will travel upward in the cylinders while valves are stuck open. Some engines are referred to as "non-interference" engines, meaning that the piston crown is designed so that it will not touch the open valves (remember that the area at the top of the cylinder when the piston reaches the end of its stroke is quite tight). Other engines might allow the pistons to make contact with the open valves, bending the valve stems, punching holes in the pistons and generally wrecking the engine internally. 

Most manufacturers recommend a timing belt change at about 50-70,000 miles, although this can vary. Consult your Audi Owner's Manual for details or contact our service department.

What's Involved in Timing Belt Service? 

While timing belt service is fairly routine, it's also an involved job that requires disassembly of several systems and components and should only be done by factory-certified techs. The timing belt also uses a tensioner, a spring-loaded idler-style device that keeps it at recommended tension. The tensioner needs to be changed as part of this job, and the service department will also inspect the water pump as part of the service. 

One thing for sure - every mile that you exceed the service interval is borrowed time. If your Audi is coming up on service have your timing belt checked, don't delay. Schedule an appointment with us at Audi St. Paul, where you can count on OEM Audi parts and factory-certified service.