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By Counterman
You might not be able to see it, but an accessory-drive belt is always both speeding up and slowing down. When a piston accelerates downward after the ignition of the fuel and air, the crankshaft speeds up and then slows down as it reaches the bottom of the stroke. These changes in speed are minimal, but big enough to cause problems over time.
If the pulses aren’t minimized, they can hammer the belt and the attached rotating components. On a four-cylinder engine, the degrees of rotation between power pulses are greater than on a V-8 – so the amount of change in speed on the four-cylinder pulley is greater than on a V-6 or V-8. This has a direct effect on how the belt system is designed.
The belt-drive system is working hardest when the engine is at idle. When the engine is below 1,000 rpm, the alternator, A/C compressor and power-steering pump are putting the greatest strain on the belt.
Some of the forces can be taken up by the belt slipping on the pulleys. But, slipping causes friction and wear on the belt, as well as flutter. Over time, the slipping can get worse as removal of material from the ribs causes the belt to bottom out.
There are three components that help to keep the belt on the pulleys without slipping. The tensioner, harmonic balancer and decoupler pulley work together to keep the accessory-belt system quiet and the belt lasting until the replacement interval.
Tensioner
The tensioner applies force on the belt. Some tensioners have devices that dampen the movement of the spring and arm, helping to keep constant force on the belt even under a wide variety of conditions.
Harmonic Balancer
The harmonic dampener puts a layer of soft material between the crankshaft and outer ring of the pulley. The material helps to dissipate the power pulses and resonant frequencies. While the dampener may only flex one or two degrees of movement, this takes a lot of strain off attached components.
Decoupler Pulley
Some alternators have a decoupler pulley. This device serves two purposes. First, it helps to decouple the pulley from the alternator with a one-way clutch. The decoupler reduces parasitic losses by not having to fight against the momentum of the armature in the alternator while the engine is decelerating and accelerating.
Some decoupler pulleys have a spring and friction dampener to reduce vibration. When an alternator decoupler pulley is compromised, it can no longer absorb the same level of abuse, which has a trickle-down effect throughout the system.
Alternator decouplers and pulleys should be inspected every 10,000 miles for wear. Early design versions have a service life of 40,000 to 60,000 miles, with more recent versions lasting more than 100,000 miles.
When inspecting a decoupler or pulley, there are two signs that replacement is needed. First, after shutting down the engine, if there’s an audible buzzing, the bearings in the pulley have likely failed. The second sign depends on whether the vehicle has a one-way clutch (OWC), overrunning alternator pulley (OAP) or decoupler (OAD).
With the inspection cap/cover removed and the center locked, turn the pulley or decoupler with the appropriate tool. If it’s an OAP or OWC, the pulley can only be turned in the clockwise direction. If it’s an OAD, a counterclockwise turn will reveal a noticeable increase in spring force; a clockwise turn will only have slight resistance. The tensioner, harmonic balancer and decoupler pulley work together to keep the belt in contact with grooves in the pulleys. The three components are engineered together to match the engine. If one part is compromised, all are compromised, including the belt.
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By NAPA
Your engine’s
link hidden, please login to view is probably not something you check on very often. If it is working then your vehicle will run, the battery will charge, the power steering works, and the engine stays cool. But if that belt were to break you will likely be stuck on the side of the road waiting for a tow truck. That’s why it is important to learn the signs of a bad serpentine belt before it fails. Cracking
One of the common signs of bad serpentine belt condition is cracking. With the engine turned off, pop the hood and grab a flashlight to inspect the serpentine belt. If you see more than three cracks in the belt along the same three inch section, it is time for replacement. Be aware though that some modern serpentine belts are made from materials like EPDM (ethylene propylene diene monomer). These materials are highly resistant to cracking, so a belt that is well past its prime may still look good with no cracking, so it is best to keep checking for other wear indicators if you suspect a worn belt.
Squealing
A belt that is no longer able to grip the engine pulleys may begin to squeal as it slides over them rather than spinning them. This leans to even more accelerated wear of the belt as well as putting heat into the belt via friction. Even if the squealing goes away, don’t ignore it. Normal serpentine belt operation should be nearly silent.
A
link hidden, please login to view can also cause the serpentine belt to slip so be sure to check it or else your new serpentine belt may have a short service life. If the belt is chirping like a bird the problem might be one or more accessory pulleys are out of alignment. Not only is this annoying but it will also cause the serpentine belt to wear out faster or even cause the belt to come off.
Worn Out
Modern serpentine belts are actually pretty well engineered to resist physical damage. But just because a belt isn’t cracked or falling apart doesn’t mean it is still good. Just like a car tire the surface material on a belt can wear down. When this happens the ribs on the belt lose their original tight tolerances, and therefore their grip on the engine pulleys. The belt may still fit fine on the pulleys, but it won’t be fully contacting the pulley. The belt may actually end up riding on just the pulley ridges which makes for a tiny contact patch.
Mileage
Even the best serpentine belt doesn’t last forever. If you have been inspecting your serpentine belt regularly and it still looks fine, you should still replace it every 90,000 regardless. Even without any of the signs of worn serpentine belt life racking up that much mileage means it is time for the belt to move on. If you can’t remember when you change your serpentine belt, it is probably time.
Electrical Gremlins
One of the lesser known signs of bad serpentine belt condition is an electrical system that starts to act up. Modern vehicles are chock full of computers, modules, sensors and more components that rely on certain conditions to remain constant, like voltage. If the serpentine belt is worn to the point where it no longer spins the alternator consistently there could be variation in alternator output. You may even get a check engine light for random systems issues. If you are pulling your hair out chasing electrical issues, check the alternator output for consistency. If it is jumping all over the place a worn serpentine belt may be the issue.
Not So Cold AC
Another one of the not so common signs of a worn serpentine belt can be a weak AC system. Your air conditioning compressor takes a bit of engine power to turn. You’ve probably noticed that in a car with a small engine turning off the AC feels like it gives you a bit of a power boost. If the serpentine belt can’t grip the AC compressor clutch, it also can spin it to compress the refrigerant back into a liquid to cool you off. You might hear a squealing sound when the AC compressor cycles on, but don’t rely on sound as the only symptom. If your AC isn’t blowing as cold as you remember and you can’t remember when you changed the serpentine belt, it is probably time for a belt replacement.
Diagnosing a worn out serpentine belt isn’t as easy as it used to be, but the signs are all there if you are paying attention. Luckily serpentine belts are usually affordable and
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By Counterman
For the first time, Adventry Corp. planned to display its Goodyear Belt heavy-duty line of products at Heavy Duty Aftermarket Week (HDAW) in Grapevine, Texas, this week.
Goodyear Belts is a licensee collaboration between Adventry and The Goodyear Tire & Rubber Company.
“Our team has worked hard to develop a full range of V-belts, serpentine belts, tensioners and pulleys for heavy-duty applications,” said Tara Cevallos, CEO of Adventry. “Heavy-duty aftermarket professionals expect great products and that’s what we deliver, along with our outstanding service.”
“We currently have more than 1,800 SKU’s, covering more than 98% of the market,“ said Chad Davis, senior product manager at Adventry. “In addition to our complete line of the highest-quality belts, the new Goodyear tensioner, pulley and FEAD Kit program is ideally suited for the needs of distributors, fleet managers and professional installers. Our customers have found our online catalog is second to none.”
Goodyear Belts’ new line of heavy-duty power-transmission products meets or exceeds OEM specifications. Belt materials have been developed and tested to provide dependable and durable service. Goodyear tensioners, pulleys and FEAD kits are designed to restore an engine’s serpentine belt drive to original specifications. For more information, visit booth 1834 at HDAW,
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By Counterman
If you were buying a new vehicle, what would you want the engine to have: a timing belt or a timing chain? You may have an opinion, you may not. Either way, let’s compare the two; then you can decide.
The Chain Gang
For many years, timing chains were the go-to for engine design. Generally speaking, they were dependable and didn’t require any specific maintenance. They were lubricated by the engine oil, so if you changed it on a regular basis, the timing chain would hold up well.
Or would they? A lot of people still say, “They don’t build them like they used to.” This is true, and coming from someone who is an old-car enthusiast, I’ll defend a level of workmanship that we don’t see in today’s vehicle. But the statement, while true, doesn’t always mean they built them better.
In the case of timing chains, they sometimes wore quicker than a lot of people realized. What happened when they did? On an old car, nothing right away. At least nothing of which the owner was aware.
A timing chain, just like a belt, is there for one reason: to connect the crankshaft to the camshaft at exact points so the valves open and close at the correct time for engine operation. A traditional, old-school timing chain was tight upon installation, and the overall timing set consisted of a crankshaft gear, a camshaft gear and a chain. There was no adjustment or no tensioner.
When the chain or the drive gears began to wear, engine performance would suffer, but it would degrade slowly, and most vehicle owners had no idea there was a problem. They wouldn’t know at all until they started to get a hard-start or no-start symptom. And why? There was no crank sensor or cam sensor, and no computer to translate the signals into a crank/cam correlation diagnostic trouble code (DTC). So, we just drove the cars until they wouldn’t drive any more.
Early engine design was split between gears or chains, but chains ultimately became more popular because they took up less space and ran quieter, and by the early ‘80s, the majority of cars produced had timing chains.
An evolutionary change of timing-chain design included nylon-tooth cam gears. They ran quieter than a traditional steel gear, but they wore out a lot quicker and created problems long before vehicle owners expected, which didn’t do much for their reputation. The tried-and-true timing chain was simple and generally dependable, but times were changing.
Buckle Your Belt
As the ‘80s rolled on, electronics, emission controls and technology were on solid cruise control and like flipping a switch, timing belts were suddenly in the picture.
Although timing-belt-driven overhead camshaft engines weren’t new by any means, the value of the design began to be recognized and auto manufacturers started to change over to this concept. The camshaft was now located on the cylinder head, which eliminated push rods and, on some designs, the rocker arms were eliminated as well, saving weight, lowering cost, reducing valvetrain inertia and making multi-valve designs possible.
The easiest way to drive the camshaft was via a timing belt. Since timing chains suffered from inherent gear wear and stretching, engineers decided that belts were the way to go. They were quieter and lighter than a chain and less expensive to manufacture.
The tensioning systems were simple, and the belts remained tight for a long time without wearing the cam or crank gear.
Seemingly, all was good, but even with the advantages of a timing belt, they required replacement at specific intervals, and the one disadvantage that became known quickly was that if not replaced, they would break with no warning. Simple tensioning systems required adjustment from time to time, and oil leaks also were a problem with timing belts, as they would degrade the rubber quickly and lead to a broken belt. A broken belt could mean a very expensive repair on interference engines.
Belt quality and tensioner design improved quickly, eliminating many of the early timing belt troubles, and by the mid- to late-‘90s, timing belts were used on the majority of automobile engines. Belt-service intervals became longer, and consumers were getting used to this being a part of normal maintenance. But you still cannot ignore the replacement interval, and was it possible times were changing again?
The Old Ball and Chain
As we said “Happy New Year” to a whole new century, engine technology was a freight train out of control. Materials and manufacturing were better, RPMs were higher, turbochargers were boosting like never before and horsepower wars like we hadn’t seen since the ‘60s were heating up again.
Smaller engines were producing more power than ever, and variable valve timing was pushing engine performance to the limit. Just like that, engine design required something that was narrower, more durable and more dependable than a timing belt, and consumers no longer wanted the associated maintenance. Hello chains.
As of the last decade, timing chains have risen back to the top. Design is far different than that of old, with modern chains traveling around awkward paths of sprockets, hydraulic tensioners and chain guides, offering a high level of dependability and performance. But they couldn’t do it without one critical thing on their side: lubricant technology.
A primary reason for timing-chain wear always has been related to lack of oil changes, lower-quality oil, and poor or non-existent positive crankcase ventilation (PCV) systems, which wreaks havoc on engine oil.
Modern engine oil is not only far superior than it was just a few decades ago, but PCV technology also is eliminating the majority of blow-by-related contaminants and moisture from building up, resulting in cleaner oil and better lubrication throughout the engine.
Timing chains and variable valve timing systems are dependent on clean, healthy lubrication and now they have it, but then again, does everyone change oil as often as they should?
Talk to the Techs
Timing belts generally are easier to service. This is primarily because they’re located on the outside of the engine and run dry, with no lubrication. When replacing a belt, there’s less cleanup and no time required to reseal engine covers. On the other hand, the engine water pump is frequently driven by the timing belt, so when you replace it, it’s a good practice to replace the pump, as well as any tensioners or rollers.
Timing belts came into prominence along with the inline four-cylinder engine. What this brought was more than just cam/crank timing, but also balance shafts and intermediate shafts that often drove distributors and oil pumps. These weren’t hard to work with, but had to be timed correctly during belt replacement.
As the timing belt migrated to V-configuration engines, it became a lot longer with additional rollers and a more difficult installation, plus some components such as thermostats were all of a sudden underneath. Some things got better, some got worse.
Inspection is an advantage with a timing belt; it’s usually just a couple of bolts and you’re looking right at it. One problem, and a challenge especially on a second-owner vehicle: If the mileage is over that of recommended timing-belt replacement and the owner doesn’t know if it was done, replacement is always recommended.
Many belts can look great on the outside but strip the teeth off a day later. The only way to inspect them closely enough to really look at the integrity of the teeth can be to remove them. And then, does it make sense to put the old one back on, and is there a technician who would want to take that gamble? One solution to this is the bright yellow replacement decal that’s included in almost every timing-belt kit, for a technician to fill out and affix under the hood. If only they got used more often.
Timing chains, as good as they have become, are not without faults. They can be a bear to inspect and replace, mainly because they’re located inside the engine so they can be lubricated by the engine oil. There’s a lot more cleaning to do and usually a seal or two that needs replaced. Just as with belts, there’s often a water pump that’s driven by the chain that should be replaced.
While the chains are more durable and dependable, if oil changes aren’t religious, the guides have a tendency to wear out really quickly. Most guides are steel with some type of nylon or plastic that the chain rides along. Remember the nylon-tooth cam gears? These guides do the same thing and beyond a certain point in wear, the tensioner can no longer take up the slack in the chain.
This often leads to a rattling noise and a “Check Engine” light. Most engines still run perfectly fine at this point, with the most common complaint a “Check Engine” light and a cam/crank correlation DTC.
Timing-chain replacement is often very expensive due to labor time, but, then again, so is engine repair when a timing belt breaks. They both require special tools at times, so there’s no winner on that argument. And, one more thing: Did we mention the latest technology of belt-in-oil drive systems? Here we go again. So, do you have a preference, or do you agree with my conclusion?
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By OReilly Auto Parts
These step-by-step instructions and video detail a serpentine belt replacement on a 2012 Ford F-150 XLT, and will be similar for ...
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