A serpentine belt problem is one of the more serious car problems.

Not serious in terms of replacement but rather in terms of the consequences it may have if neglected or not recognized on time.

This belt has a huge and important role in the proper functioning of your car. So, if you don’t take action on time, it may cause severe damage.

In order to do so, you have to know what are some of the most common signs and symptoms of a serpentine belt problem.

Hopefully, this article will give you some insight on that topic and enable you to get the upper hand.

Besides this, at the end of this article you can find some of the reasons that cause a serpentine belt problem.




Before we start, I guess it wouldn’t hurt to say a few things about this important belt.

In a nutshell, it’s a continuous belt that drives all of the major devices needed for the proper functioning of the engine and the whole car.

By devices I mean mainly the alternator, in some cases the water pump (in modern cars it tends to be driven by the timing belt), air condition compressor and power steering pump. There may be more all depending on the type of car and engine.

All of these devices depend on engine power which is delivered via the crankshaft pulley. The serpentine belt is essentially a connection between the crankshaft pulley and the pulleys of other devices.

So, this is why noticing and solving a serpentine belt problem on time is so important. Neglecting it may cause major failure and damage to your car (loss of electric power, loss of power steering, overheating or else).

If you want a more thorough definition about the serpentine belt, click here for a great one on Wikipedia.





This symptom is one of the most recognizable ones. It’s manifested as a high-pitched sound coming from the engine bay.

It’s one of a kind and gives most drivers goose bumps and the impression that something more severe is wrong.

The main reason, in most cases, will be a stuck pulley from one of the devices (alternator, AC compressor, power steering pump etc) or a tensioner.

A stuck pulley is mostly caused by a worn out bearing.

The belt slides over a motionless pulley causing extensive friction, heat and the recognizable sound.

The screeching sound may also be caused by a severely worn out serpentine belt (in this case, it must be nearly pulverized).


This sound is the first warning of a serpentine belt problem to come, especially if it’s present all the time.

It’s a weak, sometimes barely noticeable squeaky sound that may even disappear when you start to drive or the engine heats up a bit.

Squeaking is caused because the belt is slipping over the pulleys.

The slipping is caused because the belt loses ability to produce enough friction between itself and the pulleys (mostly due to material fatigue).

As soon as you notice this sign, inspect the belt and make a replacement as soon as possible.

Other reasons could be:

  • the surface of the belt may be contaminated with things like or oil or coolant. In this case, make a thorough inspection as soon as possible as you may have a bigger problem.
  • faulty tensioner. If the belt can’t be properly tensioned, it slips and causes these kinds of sounds.



If cracks and frayed edges appear on the serpentine belt, this is a sure sign of a problem.

The causes will be either material fatigue of the belt or a damaged pulley. In some more rare cases, belt misalignment can cause the problems.

Whatever the case may be, make a replacement as soon as possible so the belt doesn’t snap.

In order to spot this symptom best check the belt from time to time. You don’t have to do anything special; just take a glimpse when making a regular car check up.

If you don’t have a habit of regular check ups or lack the knowledge to do so, you can click here for our page dedicated exclusively to this topic.




One more crucial device driven by the serpentine belt is the alternator.

It’s in charge of providing the car with electric power. It’s proper function and voltage output highly depend on good condition of the belt.

So, if it’s worn out, it will start slipping over the alternator pulley and the alternator won’t be able to produce enough electric power.

This symptom of a serpentine belt problem is notorious for being hard to recognize. In most cases, there will be no sounds or visible symptoms. To make things even harder, even the battery light doesn’t come up.

Simply, the alternator continues producing electric power but at a lower capacity.

You can drive the car for some time without noticing any problems. Eventually, because of battery discharge, the lights will get dimmer and the car will start to crank poorly. Only then will you notice that you have a problem.

Main cause of this problem is material fatigue of the belt so changing it on time will probably prevent this.




If the battery warning light comes up while driving, the serpentine belt is the first thing to check.

There are two “glow levels” of the battery light if you have a serpentine belt problem:

  • Fully glowing and comes up in a moment’s notice

This is the case if the belt snapped or fell off.

The battery warning light comes up because the alternator has completely stopped working as there is no rotation.

If the belt snaps like this, the main reason would be serious material fatigue and neglecting the problem for a long time.

On the other hand, if the belt fell off the pulleys (it’s in good shape but jest fell off), you should first check for damaged pulleys or a weak tensioner.

Pulleys tend to wear out or fall apart in some cases while damaged tensioners loosen the serpentine belt.

  • Weak glow of the battery warning light

When you have a weak glow on the dashboard it could mean the serpentine belt is severely slipping.

In this case, the alternator is barely producing enough voltage output (hens the warning light).

With this symptom occurring, the belt is probably on its last legs so make a replacement as soon as possible.

It can also be loose, so check the tensioner, besides the belt. All of this can be accompanied by the mentioned weak squeaky sound.

Of course there may be other reasons for a battery warning light coming up on the dashboard. If you’re interested in this topic you can read a separate article by clicking here.





Another important device driven by the serpentine belt is the water pump.

This is not always the case as on a lot of cars the water pump is driven by the timing belt.

You should have this in mind so you don’t falsely “accuse” the serpentine belt for overheating.

Anyway, if the belt does drive the water pump on your car and it’s worn out, it can slip over the pump pulley causing reduced coolant circulation in the engine.

Even worse, if the belt has snapped or fallen of the pulley, it can cause a complete stop of the coolant circulation.

In both cases slower or faster engine overheating is imminent. This can lead to severe engine damage (like a complete or partial engine overhaul).

So, if you see the temperature gauge needle going slowly or instantaneously over the middle, pull aside as soon as possible and check the belt.

Besides the belt, there are other reasons for an overheating car. If you’re interested, you can see these reasons in a separate article by clicking here.




When you turn the steering wheel and it doesn’t go as easy and smooth as it should, it might be due to a serpentine belt problem.

Power steering is possible because of the steering pump which is driven by the serpentine belt.

If the belt is worn out, it can’t overcome the resistance of the pump causing it to work at lower capacity.

In this case, the power steering will work but just slightly. You can turn the wheel but not as easy as usual.

If the belt snaps or falls of the pulley, the power steering will be completely gone in a moment’s notice..

The steering wheel will turn heavily (like in older cars where there was no power steering at all).




As with the other devices, the serpentine belt turns the AC compressor also. The proper function of the whole air conditioning depends on the belt being in good shape.

If it slips the air condition will be weak (mainly in terms of cooling).

This is because the compressor will work at a lower capacity.

However, if the belt snaps or completely falls of the pulley, it will stop working altogether as the compressor itself will stop turning.

So, if you turn the AC system on and it’s weak or not working at all, you might have a serpentine belt problem.



In most cases, this is not a sign of an emergency and the belt can last some more.

It’s rather a tell-tale sign of a serpentine belt problem in the near future.

Most common reason for this is higher air humidity in the morning combined with a belt that’s nearing its end.

Very small amounts of water appear on the serpentine belt in the morning acting as sort of lubricant, causing the belt to slip.

This, combined with the beginning of belt material fatigue will cause this sound.

It usually disappears once the belt warms up a bit (like 10 to 20 seconds after the engine is started).

When you hear this sound, best make an inspection.

In most cases, the belt may still be in good shape but have in mind that a serpentine belt replacement may be near.




This sign is the most obvious one and it happens if the belt has snapped or fallen off the pulleys completely.

If you look under the car or around the pulleys under the hood and see a hanging belt and bits of it, there’s no doubt of what’s wrong.

In most cases, it happens at a moment’s notice without any warning making it very dangerous.

On some cars it may even get tangled with the timing belt causing huge damage to the engine.

Most common reason for this mishap is a severely worn out serpentine belt. By severely I mean barely hanging together on its last threads.

Other common reasons may be a damaged pulley (shreds the belt) or damaged/loose tensioner (belt is loose and falls of).

You should never let the problem get to this stage. The belt will first be cracked and have frayed edges before snapping. A strong squeaky sound will probably appear also.

It’s a rare case that a belt in good condition will snap and if it does, it must be due to some kind of instant physical damage.

So, to prevent this whole ordeal, make a serpentine belt replacement on time and inspect it regularly.



After reading these signs and symptoms you’ve already probably concluded what are the reasons for a serpentine belt problem.

Nevertheless we’ll make a brief recap so you may find the cause of the problem more easily.

Here we go:

1. Lack of regular maintenance



Lack of maintenance simply means you haven’t changed the belt on time.

This is, by far, the most common reason for a serpentine belt problem.

When material fatigues starts to seriously affect the belt it will start to slip, crack and get frayed edges.

Eventually, it will snap or fall off if the problem is not tended to.

Oil or coolant leaks can also affect the serpentine belt and cause problems. If they get on the belt it may cause slipping and damage to the belt surface. Proper maintenance should also prevent this problem.

Faulty or worn out tensioners will also be solved by regular maintenance and especially by using quality parts.

All in all, if you mean good for your car and for yourself, do regular maintenance and use quality spare parts. Serpentine belt or otherwise.

This will assure that you never encounter this problem again.

2. Damaged or misaligned pulleys


Although pulleys are made of very durable metal or plastic material, they too are susceptible to material fatigue.

Billions of rotations under constant tension of the serpentine belt will take its toll over time.

The “ribs” in the pulleys get damaged so even if you change the belt, the damaged pulley will tear and shred the belt again.

Don’t forget that the belt is made for double-sided use also; a damaged pulley can also wear out the other, smooth side of the serpentine belt too.

About misalignment;  it usually happens if some of the devices have been previously removed, repaired and not returned in to place properly (all of the pulleys are not in line).

This means the belt doesn’t rotate in a straight line but gets twisted to one side causing excessive wear and damage to it.

3. Damaged devices (alternator, AC compressor, power steering pump etc)


If the mentioned devices are not working properly, this will cause a serpentine belt problem.

For instance:  if you have alternator problems like a damaged bearing, the rotor won’t turn properly, neither will the pulley and this will then damage the belt.

The same case is with all the other devices that are belt driven.

In order to avoid these kind of problems a simple pulley check is performed, by hand, when changing the serpentine belt.

They are turned and if there is no resistance and grinding sounds, the belt can be replaced.

However, if there is resistance (like from a faulty bearing), changing the belt will be useless. It will soon get damaged again due to extra tension and wear.

You have to repair the faulty device as soon as possible.

Remember that all of these devices have a maintenance interval of their own and making them on time means less serpentine belt problems.



Written by: Sibin Spasojevic


Former car technician, life-long car and DIY enthusiast, author for Despairrepair.com