One of the top causes of roadside failure is the breaking of the drive belt. This catastrophic failure many times sends the vehicle to an early grave. The good news is that properly maintained belt systems seldom end a car’s life. The bad news is that a driver who delays the maintenance of the belt system could suffer the loss of a vehicle.
The drive belt system is made up of belts, tensioners, pulleys, bearings, and possibly an overrunning alternator decoupler (OAD). Proactive maintenance requires the system to be checked a minimum of every 10,000 miles, but many shops like Hi-Tech check it with every oil change.
Mechanics can quickly inspect the belt system, but drivers can also check the system by listening to the sounds under the hood. There are three specific noises to listen for when doing a sound check:
- A buzz suggests a potential OAD failure.
- A chirping sound suggests a misaligned or worn belt or pulley.
- A squeal suggests low belt tension or pulley drag.
The above sounds can show up under several different sets of circumstances. A squealing, during the initial startup of the vehicle or when parking, is a tried and true clue of a pending failure. When tensioners and pulleys wear out, they too cause noise and vibrations. If the pulley is already damaged, it can cause extensive tension that’ll significantly increase the noise and vibration.
Here is the full checklist used by mechanics:
- Engine light on (from belt slippage or overheating due to belt problems)
- High mileage
- Belt noise
- Belt wear
- Belt flutter (caused by too little tension – indicates a worn tensioner)
- Erratic belt movement, poor track
- Tensioner out of range
- Tensioner stuck or jammed
- Tensioner damaged or worn
- Tensioner, pulley corrosion
- Rough pulley bearings
- Leaking pulley grease wheels
- OAD wear or failure
To avoid the domino effect, mechanics check the surface side (ribs) of all belts and the edge (flanks) to make sure the belts are wearing uniformly. Most belts have an expected life of 60,000 – 90,000 miles, but belt problems due to heat and external conditions can quickly lead to irreparable engine damage if it goes unchecked.
Here are several things that can happen when the belts wear unevenly:
- Rib Wear is typically caused by high mileage, misalignment or defective pulley bearings.
- Glazing is a shiny, hardening of the belt due to aging.
- Backside damage causes a defective pulley.
- Cracking tends to happen with improper tension or excessive mileage.
- Chunks breaking out from the belt can also be caused by extensive mileage, but more often is caused by excessive heat degradation or belt slippage.
- Pilling occurs with misalignment, low tension, worn pulleys, fluid contamination or a combination of the same.
- Abrasions on the belt are typically caused by slippage or debris in the drive.
- Misalignment causes noticeable noise, while kinking or twisting the belt.
- Improper installation of the belt can cause most of the above.
Many people hesitate to replace a belt because it seems like mechanics use it as an up-sale item, especially when a belt seems okay at first glance from an amateur’s perspective. Here are some facts that will help in the decision making process:
- It only takes 5% of surface wear for slippage to occur.
- A belt slipping 10% of the time can impact a car’s drivability.
- Two cracks within two inches of the surface section (rib) means the belt has used up 80% of its lifespan.
- Serpentine belts drive three systems: cooling, power steering, and charging output.
- One broken belt equals one broken down car.
Belts need to be checked regularly by a trusted mechanic. Bad belts also must be replaced immediately to spare the vehicle from catastrophic failure. Checking the owners manual will help drivers to better understand how to create a schedule to keep all the belts functioning at a high level of performance.