Auto Service World
News   October 4, 2022   by Adam Malik

From the magazine: Breaking Belts

Don’t replace just the belt, replace the entire system. Here’s why, and how it will save your customers plenty of grief

The front-end drive system belt isn’t what it used to be. It was a different time in the 1980s when serpentine belts first become available. They used to just drive the water pump and alternator. Other belts would help drive other accessories.

Belts weren’t dealing with a lot of sharp angles. There was usually a screw-type or manual tensioner. So frequent re-tensioning was commonplace for technicians.

But that’s not the case today. Just about every vehicle these days has only one belt. It’s longer and runs at sharp angles. As vehicles have evolved, so has the belt. It’s now made of EPDM, a hard rubber compound that lasts a long time — about 100,000 miles, or 160,000 km.

Some experts believe once a vehicle hits the 90,000-mile or about 145,000 km, shops should be talking to the vehicle owner about replacing the entire front-end system.

Yes, the entire system: The belt, the tension and pulleys — not just the belt.

That’s because replacing the belt is akin to a band-aid solution. There are deeper issues that need to be taken care of at the same time. If not, your customer will be back in your shop again because of the belt. And they’ll probably be agitated.

Belts are a common replacement item, noted Tom Lee, marketing manager of automotive aftermarket products at Continental. They should be checked during every oil change and at least every 30,000 miles (50,00 km).

“In addition, belt inspection should include all aspects and components of the serpentine belt drive, which includes tensioners and pulleys,” he added.

“When you have a silly comeback like that from a fan belt, it just looks bad. And it erodes the customers’ confidence in your shop.”

Doing the job right means having all components replaced, according to experts. That way, the customer should get another 100,000 miles of performance, according to expert estimates. But just replacing the belt cuts that down to 30,000 miles at best.

“It’s coming back because of the belt problem, usually because of noise or, typically, a chirp. And why is that? It’s because the tensioner and pulleys are now worn out,” explained Jay Buckley, Dayco’s head of product management and tech team lead.

The issue shops run into is that the owner’s manual will instruct belt replacement at 100,000 miles. Shops will follow that guidance. But experts advised that the job doesn’t end there. More needs to be done to the vehicle to avoid a customer comeback.

“When you have a silly comeback like that from a fan belt, it just looks bad. And it erodes the customers’ confidence in your shop,” Buckley said.

To avoid that, replace the tensioner and the pulleys at the same time as the belt.

“It’s a system that’s designed to work together. Now you’re giving that new belt the opportunity to go another 100,000 miles with no issues,” Buckley told CARS.

The belt is a key component of ensuring a vehicle is safe and reliable. Should it break on a customer, the vehicle is essentially dead on the side of the road.

“Most cars on the road today have a single belt drive system that runs all the important accessories including the alternator, AC compressor, power steering and water pump,” Lee said. “The belt is running these accessories from both sides and is working harder than ever. Should this single belt fail, the results can be catastrophic, leaving you and the car on the side of the road with a very large tow bill.”

Shops should be telling the customer that “we want your new belt system to last another 100,000 miles without thinking about it, without worrying about it, [while] going on a trip or anything else,” Buckley said.


A simple visual inspection isn’t enough to give a belt the green light. “Typically, technicians look at a belt and they’re … checking for cracks on the belt and using that as an indicator of to replace it. That’s really not a good way to do it,” he said.

Buckley and Lee recommended treating belts like tires — use a tool to gauge its remaining life, if any. These tools are generally available from suppliers. Check for irregular movement and slippage as well.

“Friction builds between a belt and the drive system components, like a tire rotating down the road, wearing away at the tops and sides,” Lee told CARS. “A belt begins to slip when the grooves of the belt and grooves of the pulley no longer connect. Belt tension is critical and weak tension results in belt slippage. If the belt, idlers or tensioner are not operating as new, the drive will show problems and will eventually fail.”

It should also be easy to visually inspect the status of the tensioner and pulleys.

“Honestly, you cannot even check a tensioner or pulley without taking the belt off. When they’re under tension, any play in the bearings is not obvious or noticeable,” Buckley said in an interview.

“Spotting and diagnosing belt noise and belt wear problems is very important,” Lee said. “Serpentine belts made of rubber will wear and fail over time. In addition, tensioners and pulleys have bearings and seals that will wear and fail over time.”

Once the belt is off, spin the pulley. If it rotates more than once, there’s no grease left in the bearing and needs to be replaced. If it rocks from side to side, the bearings are worn out and replacement is needed. Techs can put a wrench on the tensioner and move it through its full range of motion while observing the body of the tensioner.

“If the body moves and tensioners are starting to come apart, if it doesn’t feel smooth through its entire movement, then again the bushings inside of it are starting to wear,” Buckley explained.

“Idler pulleys have bearings and seals that can fail and cause noise. In addition, due to the loads put on them, bearings within the idler and tensioner wear and fail,” Lee said.


Shops should be able to get a kit from their jobber that will have the belt, a tensioner and a pulley.

“Most of them are just not any more complex than that. If they are, they’ll have maybe two pulleys or three pulleys and in there, but usually only one tensioner,” according to Buckley.

Usually, these kits will save a shop 10-15 per cent in costs compared to buying each component individually.

And for the customer, they can get all the labour done at once rather than all over again when the belt fails due to the other components not being replaced. So they’re set for 100,000 miles instead of 30,000 miles.

“One kit part number can save the installer from having to source multiple components from multiple suppliers,” Lee noted.

But don’t forget the reputational costs that would come from not doing the work right the first time, experts noted.

When Buckley owned his own shop, he would advise the customer that by only replacing the belt, he could warranty the work for only one year. But replacing the system would give a 100,000-mile warranty. When given the opportunity to think if they really want to come back to the shop and have to deal with this issue again, Buckley finds customers opt for the full replacement.

“I usually don’t have much trouble to sell the systems approach,” he said. “You’re really taking care of your customer when you do that. You’re doing the right thing for them to keep their car running well and not have issues when it’s not in the shop.”

This article originally appeared in the July/August 2022 issue of CARS magazine

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