Auto Service World
Feature   December 1, 2003   by Rick Cogbill

Belts and Hoses — The Changing Scene

It's standard under-hood procedure: A vehicle comes in for a winter check over, and along with testing the antifreeze you do a quick inspection on the belts and hoses. Considered the "soft" component ...

It’s standard under-hood procedure: A vehicle comes in for a winter check over, and along with testing the antifreeze you do a quick inspection on the belts and hoses. Considered the “soft” component of the modern engine, we know these flexible parts don’t last forever, and certainly not as long as most of the “hard parts” they’re attached to. But lately there’s been some changes going on underneath the hood, and it’s time to take a closer look.


Besides the usual enemies like heat, vibration, oil and grease, or external chafing, coolant hoses are also being attacked from the inside out by something called electrochemical degradation, or ECD. A four-year study on fleet vehicles by Gates engineers showed that virtually every vehicle, regardless of mileage, had some form of ECD.

It’s caused by the fact that the hose, the coolant, and the engine/radiator fittings form a galvanic cell, which is basically a battery. This chemical reaction causes micro-cracks to form, called striations, which allow coolant to permeate the hose and attack the inner reinforcement. Add heat and flexing, and you’ve got a recipe for cooling system disaster.

ECD occurs within two inches of the hose fittings, and Guy Enta, National Sales Manger for Goodyear Canada, offers this advice: “After the engine has cooled, give the hose a pinch a few inches from the connectors. You may feel gaps where the hose has been weakened by striations. Then squeeze the middle of the hose. If the end feels softer than the middle, you may have tracked down the invisible enemy. In this case, change the hose immediately.” Striations occur faster where the combination of high heat and air pockets exists, explaining why the upper radiator hose often fails first.

Because surveys showed that hose replacement doubles or triples within the fifth year of ownership, the industry-recommended hose replacement interval used to be every four years. But technology is changing. Hose manufacturers have recently come up with electrochemically-resistant hoses (ECR) to meet the electrochemical requirements as specified in standard SAE J1684. Using new compounds, hoses are now virtually unaffected by electrochemical degradation. Where old hoses once showed degradation symptoms within 25,000 miles (in the Gates field test), the new compounds are still going strong after 200,000 miles.

Casey Wnuk, Western Sales Manager for Dayco, says they now use the new compounds in all their hoses (as does Goodyear and Gates). “The change in compounds, and the changes in the glycol being used are making hoses last a lot longer.” At one time, 100,000 km was their benchmark for belt and hose replacement, says Wnuk. “But our product is lasting longer now. In fact, we’re being criticized that we’re making our product too good.”

So what does this mean for the replacement market? “There is no magic number we use for coolant hoses other than recommended regular inspection,” says Goodyear’s Guy Enta, adding that striation-resistant coolant hoses are basically unaffected by ECD. “Bottom line,” he says, “now that we know striation exists, a more appropriate recommendation is to run a quick check for it and change the hoses if striation is found, versus a ‘change every X years’ rule of thumb.”


Ever since 1979, when Dayco developed the first multi-ribbed belt for the Ford Mustang, the term ‘fan belt’ has slowly become pass. As Wnuk points out, everyone has seen a drop in the V-belt market as more vehicles go the serpentine route. Dayco’s Poly Cog belt is the ‘cogged’ version of the multi-ribbed belt, with its transverse-groove design allowing more flexibility. The increased airflow around the belt makes it run cooler (up to 50 degrees Fahrenheit), and the reduced rib cracking has increased the life by at least 40%.

Goodyear has come out with its own version, called the Gatorback, using an angle-grooved Helicog tooth design. “Our construction and technological advances continue to extend belt life and performance standards,” says Enta. They also address noise issues. Besides being more flexible and cooler, the Gatorback also runs up to 15 decibels quieter than standard belts.

The causes of drive belt failure are many. “In general,” Enta advises, “look for any physical damage (chunking of the rubber, cracking, edge damage, “glazing”, exposed cords, uneven wear) or tension (over or under) issues.” With the standard belts, 4 – 5 cracks per inch remains the industry standard for replacement.

But the big key to successful serpentine belt service is proper pulley alignment and belt tension. “Our biggest problem in warranty comebacks,” says Wnuk, “is misaligned tensioners or pulleys.” Most of the belt failures they see today, whether it’s premature wear or noise problems, are the result of weak or misaligned tensioners and pulleys.

To combat this problem, Gates created the DriveAlign Laser Alignment tool, allowing installers to accurately inspect an engine’s serpentine belt drive system for misalignment. This tool quickly identifies the two most common types of pulley misalignment – offset and angular. Within minutes installers can easily measure alignment to less than 1/2 degree on the entire drive system. It’s also a great way to legitimately increase add-on sales while guarding against costly warranty claims.

Guy Enta confirms that tensioners and pulleys are a fast growing market. “Goodyear is constantly adding new numbers to increase our coverage and keep up with market demands.” Nowhere is this truer than in the area of Timing Belt replacement, where most manufacturers now supply Timing Belt Kits, which include the belt, pulleys, and tensioners. Again, Gates engineers have determined that most timing belt comebacks are caused by a faulty timing belt idler or tensioner pulley.

And speaking of timing belts, this is one area where the recommended mileage replacement rule still holds true. Because they’re hard to see, difficult to get to, and can cause expensive damage if they break, manufacturers are still recommending that timing belts be replaced approximately every 90,000 kms.

A Shrinking Market?

With belts and hoses getting better and lasting longer, it would be logical to assume that the replacement market dollars are shrinking. But according to Enta it’s just the opposite. “In our view the overall market is growing, certainly in dollars. No question (that) our products are lasting longer and traditional markets like V-belts are on the decline, however this is being more than made up for as some OE technologies, with higher unit costs and prices, now enter the ‘replacement’ phase of their life cycle.” Add to that a proper inspection of pulleys and tensioners, and you’ve got some extra sales room. “The biggest growth area for Dayco over the past two or three years,” adds Wnuk, “has been our replacement of automatic belt tensioners and pulleys.”

All manufacturers offer service bulletins and speciality tools that make the job of changing belts and hoses easier. They also have promotional material to help your customers understand the importance of belt and hose service. Now, more than ever, installers not only need to be experts in their field, but they must communicate it well with their clients. Times are changing, and the good installers will know how to keep up.

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