Tenacious timing belt deserves TLC

Brian Early

SPECIAL TO THE STAR

It's so important, yet seldom talked about in the automotive world.

It's your timing belt.

Timing belts are typically found in overhead cam engines, though not all OHC engines use one. Many use the timing belt's oil-bathed cousin, the timing chain, instead.

Timing belts offer reduced mechanical complexity, lower cost, less drag and are potentially quieter than chains.

But the increasing popularity of variable cam timing (which is more easily implemented with a chain) and the trend toward extended service intervals and longer warranties favour timing chains.

The expected service life of the latter is basically a vehicle's lifetime.

Even so, timing belts remain in widespread use, particularly among the import brands, so there's a good possibility that your ride has one.

This component leads a tough life.

It's continually cooked by the engine's heat and violently stirred from sub-zero slumber during cold-weather starts.

It loops back and forth over and around pulleys and gears at thousands of revolutions per minute – sometimes while having to drive a water or oil pump.

It's able to twist around freely, yet designed not to stretch appreciably, as that would alter the accuracy of the timing that it keeps.

Most timing belts are made of neoprene, reinforced with Kevlar and other high-end synthetic fibres. All have some form of teeth or cogs to prevent slippage and allow precise alignment.

The function of the timing belt (or chain or gears) is to synchronize the operation of the valves relative to the position and motion of the pistons.

The timing of these events is critical to the performance and efficiency of your engine.

Being just a few degrees out of sync can dramatically affect driveability, economy and emissions.

Should a belt break or otherwise fail to do its job, engine damage becomes a definite possibility.

Many motors have what's known as an "interference" design, meaning that when the valves are open, they extend far enough into the combustion chamber that the pistons will strike them if they are not closed in time.

It's not a happy meeting – valves bend and pistons can be ruined. A broken belt can immediately result in catastrophic engine damage, even if it occurs at idle.

With a non-interference engine, you'll need a tow truck at the very least, since the motor can't run without the belt.

Since a timing belt requires periodic maintenance, it's important to know whether your car or truck uses one. With such a stressful job, it's no surprise that this part eventually wears out.

Outside of obvious fluid leaks or abnormal noises from under the timing cover, the belt really shouldn't need attention beyond the manufacturer's specified service interval.

In my experience, not all owner's manuals mention the timing belt's service requirements. However, 96,000 km is the accepted norm in the industry, though some belts are rated for considerably longer.

Certain models will require pulley or tensioner upgrades at service time. Others that are known for idler bearing failures should have those replaced.

Any vehicle showing signs of oil leaks into the timing cover area should have faulty seals replaced. changed. Oil contamination can quickly spell death for a timing belt.

Many shops will recommend replacing the water pump on models whose pump is run by the belt, or even in cases where pump replacement requires the belt's removal.

This isn't just a cash grab.

Let's face it: the water pump's lifespan is finite, too. Frequently, it's not much longer than the belt's, so it makes sense to only do the job once.

There's often a substantial amount of redundant labour involved.

Timing belt replacement can be an expensive undertaking regardless.

Changing a belt in some economy cars can take a little more than an hour and require minimal parts. But for vehicles with poor or labour-intensive accessibility, with complex or multiple belt drives or needing special tools and procedures, the job can cost many hundreds of dollars.

A look under your hood may not reveal a timing belt's presence, as this component is nearly always enclosed behind protective covers.

If you're unsure about your vehicle's set-up, a little Internet research or consultation with your garage or dealership service department could save you a lot of expense and aggravation down the road. Consider it "time" well spent.

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