Watch your belts, experts warn

By: Steve Skinner

Complacency with modern engine belts and tensioners can cost a lot of money and down-time, warn the experts

Watch your belts, experts warn
Good investment: Wayne Cox recommends always carrying a spare serpentine belt and tensioner


Modern belts and tensioners can last many hundreds of thousands of kilometres, which is extraordinary when you think of how many billions of times the average belt would go around its pulleys in a lifetime, and how much heat is involved with a modern engine.

But an expert worth listening to recommends replacing the tensioner as a matter of course every 200,000 kilometres or so.

That’s the milestone he reached before breaking down because of a failed tensioner in the middle of Australia a couple of years back; and the milestone he’s recently used to replace a tensioner even though it appeared to be fine.

Wayne "Wally" Cox is a former winner of the Australian Trucking Association’s Craig Roseneder Award for technical and maintenance excellence in the workshop.

So as a driver he was able to get himself out of trouble when the tensioner died, but he wouldn’t have been able to do that if he wasn’t following his normal practice of carrying a spare belt, tensioner and idlers.

He recommends the same practice for the average truck driver, even though they wouldn’t have the tools and/or capability to change a belt system component themselves.

At least if drivers carry spares, there’s a reasonable chance there will be a local mechanically-minded person who can get them out of trouble, Cox reckons.

He says for the sake of just a few hundred bucks, carrying a spare belt system in the toolbox is a great investment, saving not only a lot of money in avoiding a rescue mission, but possibly days of lost time and embarrassment with customers as well.

Serpentine belts are so-called because they snake around a series of pulleys like a serpent.

The serpentine on a modern truck might power the fan, alternator, power steering, water pump and air conditioning all at once. That saves a lot of space in the engine area.

Serpentine belts – also known as "micro V" belts – consist of ribs which sit on multiple pulley grooves. A truck belt might have anywhere from 6 to 12 ribs.

Wally Cox rates them as superior to the older "V" belts for individual pulleys, which have rows of cogs in the shape of inverted Vs running across the belt, matching to the V pattern on their pulleys and making them flexible.

One of the most prominent brands of belts and tensioners globally – along with Dayco, for example – is Gates Corporation, headquartered in the United States and like Dayco, in business for more than a century.

Gates says serpentine belts started to make their mark in the heavy duty market in the early 90s.

But the company says there has been a change in serpentine belt technology "which most technicians have not yet become used to".

That change is in what the belts are made of. The material has changed from Neoprene to EPDM, which Gates says is much longer lasting but rarely shows visual symptoms of wear.

That’s why you can no longer rely on a visual inspection and traditional signs of belt wear – including cracking; chunk out; material loss; fraying; uneven wear; shiny spots from heat/slipping; and squealing.

Check out the full feature in the October issue of ATN.


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