ɫɫ��

He says that Honda’s recommendation for years has been for Canadian vehicles to use the shorter “severe duty” schedule of 96,000 km (We’ve just reached 100,000.) He says that if it ever broke, it would cause major engine damage.

It’s a fairly expensive job, especially as he’s suggesting the water pump get changed at the same time.

Can we put this off and save up, or is he right?

Why on earth did Honda even use a belt that needs changing? Apparently the CR-V we owned before this didn’t use one.

Cam Sprocket

Your Passport, like virtually every road-going vehicle with an internal combustion engine, whether hybrid or not, has valves that open and close to facilitate the movement of air in, and exhaust out, of the cylinder, as the piston moves through its various strokes.

The timing of those valve operations in relation to the piston’s position is critical to the operation and performance of the engine. Lobes (raised bits on a camshaft that, as the shaft rotates, lift and lower the valves) — your Passport’s V6 has two — mechanically actuate the valves through some form of valve-train, and it’s these camshafts that must rotate in precise half-speed synchronization with the crankshaft for the whole thing to work.

There are a few ways to make this happen. Most engines use either a belt or one or more chains to accomplish the same goal.

Belts weigh less and create less drag (improving efficiency), are typically less noisy, wear or stretch less, to the benefit of continued timing accuracy with age and use, further maintained by periodic replacement, and are probably less costly to engineer and produce.

Chains, on the other hand, are theoretically maintenance-free, and as they are lubricated by oil already, simplify variable cam timing design (when used), as the oil-operated cam phasers don’t have to be sealed perfectly as they do on belt drives.

Chains can be more compact than a comparable belt drive. They also have improved torque capacity for driving things such as the high-pressure fuel pumps needed for direct injection.

Honda’s decision to use a timing belt on its V6 engine family, rather than a chain as in your CR-V’s four cylinder, could be for any or all of these reasons.

The frequency of timing belt maintenance varies considerably among applications; the same engine may have different requirements, depending on the model year or specific vehicle it’s in, and a 96,000-kilometre service life is not uncommon.

Timing belts are often forgotten, and many a belt has outlived its maker’s suggested lifespan, sometimes by many times.

But letting things roll indefinitely is a pretty serious gamble.

The overwhelming majority of modern engines are what’s known as “interference,” meaning that, at various times, the heads of the valves, when fully open, occupy the same space inside the cylinder as the top of the piston. When properly timed, the two components aren’t there at the same time. When the timing goes awry via a badly skipped or broken belt or chain, well … whammo!

Usually one, or more, of the valves gets bent, necessitating cylinder-head removal and repairs. Sometimes pistons get damaged, too, at which point engine-rebuilding or -replacement makes the most sense.

Suddenly a belt seems inexpensive ….

The Owner’s Manual for your Passport does suggest that, if used “regularly” in extreme temperatures (over 43C or under -29C), a 100,000-km interval should be the measure to follow.

Unless you live in an area with those weather conditions, I’d speculate that your technician is simply following what was once standard practice for earlier versions of the J-series V6. Improved belt materials and construction reduce this need today.

You should, therefore, be able to defer the belt until the manufacturer’s system calls for it (Item 4, along with spark plugs). I agree about changing the (timing-belt-driven) water pump at that time, as it requires little extra labour with the belt removed and it has a similar life expectancy. Use a factory equivalent part — I’ve experienced a high failure rate with aftermarket pumps in Honda/Acura V6s.

Ask a Mechanic is written by Brian Early, a Red Seal-certified Automotive Service Technician. You can send your questions to wheels@thestar.ca. These answers are for informational purposes only. Please consult a certified mechanic before having any work done to your vehicle.