Drive Belt replacement & repair made easy

How does a drive belt work?

A drive belt, also known as a serpentine belt or auxiliary belt, is a long rubber belt in your car’s engine. Its main job is to connect several important parts, such as the alternator, power steering pump, air conditioning compressor, and sometimes the water pump.

This belt has often incorrectly been assumed to be the timing belt. The essential thing is, if you can see the belt, it's not the timing belt, it's the auxiliary drive belt!

The auxiliary belt is driven by the crankshaft pulley at the bottom of the engine. It is held firmly against the crankshaft pulley and so when it is turning the belt goes round and turns each of the pulleys on the circuit.

The bet is held fim usually by an automatic auxiliary drive belt tensioner and often there is also one or more guide rollers on the circuit as well to position the belt around the other devices. This is one of the reasons it is also referred to as a serpentine belt, literally because it twists around like a snake.

Alternators are almost always driven by the auxiliary drive belt, which is why it is often referred to as an alternator belt, especially when it breaks, as it’s usually the most common indication that it has an issue.

The same can be said for the power steering pump, again, this is why it is often referred to as the power steering belt.

In reality, it is usually one belt that drives all the units, but some engines can have two belts to spread the load, especially if routing for one belt is not possible.

Simply put, the drive belt is like a big rubber band that connects and powers various parts of your car's engine, helping them run smoothly when the engine is on.

What does a drive belt replacement job involve?

A drive belt replacement job involves several key steps to ensure your car's engine accessories, such as the alternator, power steering pump, and air conditioning compressor, function properly. Here’s an overview of the process:

• First, the mechanic raises the car using a lift or jack to gain better access to the engine bay.
• The battery is disconnected to prevent any electrical shorts or accidents while working on the drive belt.
• The mechanic locates the drive belt, also known as the serpentine belt, and identifies the belt routing diagram, which shows the correct path of the belt around the various pulleys.
• Next, the tensioner pulley, which keeps the drive belt tight, is loosened. This allows the mechanic to slide the old belt off the pulleys easily.
• The old drive belt is removed, and the mechanic inspects the pulleys and the tensioner for any signs of wear or damage. If the tensioner or any pulleys are found to be faulty, they are typically replaced at the same time.
• The new drive belt is then routed around the pulleys according to the belt routing diagram. The mechanic ensures that the belt is correctly positioned on each pulley.
• The tensioner pulley is then adjusted to apply the correct amount of tension to the new belt, ensuring it is tight enough to function properly without slipping.
• Any components that were removed earlier to access the drive belt are reinstalled.
• The battery is reconnected, and the mechanic starts the car to test the new drive belt. They check for proper alignment and tension, ensuring that all engine accessories are operating smoothly and without any unusual noises.

This job requires skill and precision, which is why it’s best done by a professional mechanic.

How do I know whether I need a drive belt repair or replacement?

Knowing whether you need a drive belt repair or replacement involves looking out for certain signs while driving and inspecting your vehicle:

If you hear a squealing noise coming from the front of your car, especially when starting the engine or accelerating, it could indicate a worn or loose drive belt. It could be fixed with an adjustment or may need to be replaced.

Do a visual inspection: if you notice cracks, fraying, or glazing on the drive belt, it’s a strong sign that the belt is deteriorating and needs to be replaced. These visible signs of wear can lead to belt failure if not addressed.

If the belt appears shiny or glazed, it means it’s losing its grip and could start slipping. A glazed belt can’t effectively drive the pulleys, indicating it might need replacement.
* When the steering becomes heavy (PAS pump is not being turned).
* When the battery warning light is on (alternator is not being turned).
* When the engine temperature light is on (water pump is not being turned).
* The air conditioning stops working (air con compressor is not being turned).
* If the belt feels loose when you press on it, it might need adjustment. A properly tensioned belt should have minimal give. If it’s too loose, it may need tightening or replacement.
* If your car’s engine overheats, it could be due to a failing drive belt. The drive belt operates the water pump, and if it’s not functioning properly, the engine can overheat, indicating the belt might need attention.

What happens if the drive or auxiliary belt snaps?

If the auxiliary belt, also known as the serpentine belt, snaps in your car, several critical components will stop working. This belt powers the alternator (which charges the battery), power steering pump (which makes steering easier), water pump (which cools the engine), and air conditioning compressor. Without the belt, the battery will quickly drain, the engine may overheat, and steering will become very difficult.

Continuing to drive in this condition is risky and can cause severe engine damage. It's best to stop driving immediately and get the belt replaced.

How to stop auxiliary belt squealing

To stop an auxiliary belt (serpentine belt) from squealing, you can try the following steps:

• First, check the belt for wear and tear; if it's worn out or cracked, it needs to be replaced ASAP.
• If the belt is in good condition, the tensioner will need to be inspected and adjusted if necessary, as a loose belt can cause squealing. You can also clean the belt and pulleys to remove any debris or dirt that might be causing the noise.
• A DIY approach includes applying a belt dressing spray that sometimes helps reduce squealing temporarily. However, it’s best to have a mechanic inspect it, as it might indicate a more serious issue with the belt or pulleys.

Can the drive belt be replaced by a mobile mechanic?

Replacing a drive belt or auxiliary belt is a job that can be done either on the driveway or in a garage. So yes, a mobile mechanic can replace a drive belt or auxiliary belt. Mobile mechanics are equipped to perform many types of repairs and maintenance tasks on-site, including belt replacements. The key requirements are sufficient space around the vehicle to access the belt and appropriate lighting. As long as the area is safe, level, and provides enough room for the mechanic to work, a mobile mechanic is a good option.

To know more about the cost of a drive belt replacement, you can use our price estimator tool here.