How to Know Your Timing Belt Tensioner is Bad – Read the Symptoms

The belt tensioner applies pressure to the timing belt, allowing it to run smoothly without any displacement. However, when something goes wrong with the tensioner, this could lead to major catastrophic damage like engine failure.

Knowing the common symptoms of a bad timing belt tensioner is important to identifying and resolving the issues. Such symptoms of a bad tensioner include engine performance issues, starting problems, noisy movement, triggered engine light, and acceleration issues.

Additionally, the belt tensioner allows the camshaft and the crankshaft to move at a synchronized speed necessary for proper functioning.

This article will look at some of the common symptoms and causes of a bad timing belt tensioner. We will also look at how to change a tensioner’s cost and answer common questions about the tensioner.

bad belt tensioner symptoms

What is a Timing belt Tensioner, and how it works?

The timing belt tensioner is located between the crankshaft and the alternator pulleys. It applies pressure to the timing belt to ensure it is tight and runs smoothly. You can find the timing belt at the front of the engine, which rotates between the camshaft and the crankshaft.

The timing belt is made of rubber; it ensures that the crankshaft and camshaft are synchronized in an internal combustion engine. The belt ensures that the valves in the engine open and close at an accurate time in association with the position of the piston.

In addition, the timing belt keeps the internal combustion system running. It does this by turning the camshaft pulley in connection with the crankshaft pulley. By doing this, other aspects of the engine, like the intake, compression, combustion, and exhaust, are fully functional.

For the timing belt to properly grip the pulley and turn it, it needs to maintain a certain amount of pressure, keeping the belt tight. It is when the tensioner comes into play.

Furthermore, the belt tensioner has four major parts: the base, tensioner arm, spring, and pulley. The base holds other belt parts while the spring pulls the belts tight. The pulley will then further aid the movement of the belt. Then, the tensioner arm, which can be seen at the bottom of the tensioner and works against the spring, delivers enough slack so that the belt can be adjusted or removed.

When the belt tensioner is bad, it causes the belt to become loose, which could affect the engine performance and, if not checked, cause engine issues. A belt tensioner, when damaged, could also cause the belt to break.

What are the Symptoms of a bad-timing belt tensioner?

When the timing belt tensioner becomes bad, it comes with some obvious signs, including the following.

1. Engine performance issue

The timing belt is responsible for opening and closing the valve at the right time, which leads to proper ignition. The intake valve is located in the engine combustion system, and when opened, it releases the air-fuel mixture.

As we know, the engine needs the valve to open to supply the engine with air-fuel mixture to function. When the tensioner is damaged, the timing belt will not be able to function properly and level the valve either closed or opened, depending on when the damage happened. Once this happens, the engine performance will drop. 

2. Starting issue

The valve supplies the engine with a fuel mixture that will be ignited during the ignition process. Unfortunately, when the tensioner is bad, it causes the timing belt to get loose or break. When this happens, the valve supplying fuel mixtures will remain closed.

Once the valve is closed, the ignition process will not take place. It is because there is no fuel to be ignited by the plug. In this case, you would start the engine, and you may get a cranking noise but no ignition.

3. Timing belt tensioner noise

When the tensioner is damaged, a few things may happen: the timing belt becomes loose or broken, the tensioner struggles to function, and more. All these will be noticeable by a bad timing belt tensioner sound.

For instance, when the timing belt tensioner is damaged, the belt could break, affecting the pulley. Once this happens, the pulley will no longer move free, causing disturbing sounds.

What does a bad-timing belt tensioner sound like? The sound could come in the following ways.

  • Knocking sound
  • Rattling sound
  • Squeaking or squealing sound

The position of the damage as affected will determine the type of noise that comes from the engine. You need to be observant of the noise listed above when they come from the engine and act fast.

4. Triggered engine light

The engine’s activities are always monitored by the engine’s computer system to ensure that it is working according to programmed instructions in the computer. When there is an issue with the tension belt, the engine performance will go against the programmed instruction in the computer system, which will cause the computer to trigger the engine light.

In addition, the engine light tells the driver something is wrong with the engine system. The light should not be ignored.

5. Issues accelerating

You will also notice acceleration issues, as the vehicle will be sluggish even when pressing down the acceleration pedal. The engine is not being fed enough fuel mixture due to the damaged timing belt tensioner.

The intake valve will no longer open and close at the right time and will remain stuck in a position affecting the engine’s power output.

What Causes bad timing belt tensioner failure earlier

Below are some common causes of a timing belt tensioner failure.

Worn-out spring

The spring applies tension to the spring, allowing it to maintain the pressure needed to turn the various components. When the spring is worn out, it causes the belt to lose tension and loosen. 

Like many components in the vehicle, it could get worn out after the spring has been used for a long time, it could get worn out. When this happens, the entire tensioner will become too weak, which can no longer maintain the needed tension, which could cause the belt to slip out of position.

Worn-out tensioner bearing

The tension bearing pressures the timing belt, which helps drive the pulleys. When the bearing fails, it will no longer be able to provide the tension needed to drive the belt. It would cause the belt to become loose or slip out of position.

A failed tensioner bearing can also cause the belt to get misaligned or break, needing replacement.

Excessive loading

An excessive load on the timing belt causes the timing belt teeth to wear faster. As more load is placed on the belt, tension increases more than required. The belt teeth will begin to lose grip and wear.

Once this happens, the pulley will get affected, causing misalignment and bearing wear, which can affect the overall performance of the timing belt tensioner.

Failing pulley 

If there is any form of problem like dirt build-up or a failing part, it can cause an abnormal increase in the belt’s speed and wear in the belt teeth. When this happens, the belt would easily wear out and cause slips or issues with the tensioner.

Hydraulic oil leak

In a hydraulic timing belt tensioner, leaking could cause the tensioner to stop working due to hydraulic pressure. A hydraulic timing belt tensioner works like a shock absorber and uses hydraulic oil to maintain tension.

Once there is a like in the tensioner, it will lose the tension needed to keep the belt. It will also be accompanied by noise from the engine.

How to change bad timing belt tensioner

The first step to replacing a bad-timing belt tensioner is determining its location. The tensioner is usually located in front of the engine. It is a pulley mounted on a spring mechanism. Use the vehicle’s owner’s manual if you cannot properly find the tensioner, use the vehicle’s owner’s manual.

Below is a well-detailed step to change the timing belt tensioner.

  • Remove the lower covering to locate the tensioner.
  • Hold the bolt tensioner pulley in place using a battery hold-down bolt.
  • Proceed to reduce the tension on the belt and then remove it.
  • Remove the bolt holding the tensioner, which should slide right out.
  • Proceed to install the new tensional and ensure it is bolted accurately.
  • Pull the pin on the new tensioner to place tension on the timing belt

What happens if you don’t change bad timing belt tensioner?

If you do not change a bad timing belt, the engine will eventually fail, which would cost more money to fix. The engine depends on the functionality of many components, including the crankshaft, the backbone of the combustion engine. Also, the camshaft is an important part of the engine that controls the opening and closing of the intake and exhaust valves.

The timing belt connects the camshaft and the crankshaft to ensure they move synchronously. It provides that the intake and exhaust valves line up synchronously with the piston’s up and down movement.

Once the tensioner is damaged, there is not enough pressure in the belt to synchronize the movement of the camshaft and crankshaft. It essentially causes the camshaft to stop moving, which causes a series of issues with the engine.

Other engine parts will be affected once the issue is not checked and fixed. Eventually, the engine will stop and fail.

Symptoms of a Bad Timing Belt Tensioner

How much does it cost to replace the timing belt tensioner?

A timing belt tensioner would cost between $90 and $130 to replace, excluding labor costs. It will incur an extra $90 to $150 as labor costs. Actually, the price of replacing the tensioner depends on many factors, like the model of the vehicle, your location, the brand of parts, and more.

Vehicle Models Spare parts cost Approx Labor cost Approx Total Cost
Toyota Camry $39-$84 $70-$80 $109-$164
Toyota Tundra $57-$99 $53-$67 $110-$166
Kia Soul $93-$108 $84-$106 $177-$215
Volkswagen Passat $162-$251 $184-$232 $346-$484
Chevrolet Equinox $55-$112 $86-$109 $142-$221
GMC Sierra $83-$93 $53-$57 $136-$160
Honda Pilot $196-$285 $290-$366 $486-$651

How Often Should I Replace My Timing Belt Tensioner?

There is no recommended time frame to change the timing belt tensioner. However, you must check the tensioner every time you service the vehicle. The tensioner is like other parts of the timing belt or tires with a particular usage time frame.

The timing belt tensioner is expected to last for a long time; at the same time, it could get damaged for different reasons. This is why the tensioner needs to be checked periodically.

You are expected to inspect the tensioner after every 100,000 miles mark. Also, it could be checked whenever the vehicle is taken for servicing.

Important Tips to Avoid Early Timing Belt Tensioner Failure

Adopting a good maintenance culture to have a long-lasting timing belt tensioner would be best. You can adopt the following tips for a longer-lasting timing belt tension.

Check the timing belt tensioner periodically.

The running condition of the timing belt tensioner needs to be checked periodically to ensure no problem. You are required to check the tension after every 10,000 miles mark.

Periodically clean timing pulley.

Due to the location of the pulley, it is easy for dirt to accumulate in the pulley, causing issues to arise. The pulley will fail to support the timing belt, causing problems with the tensioner.

Watch out for engine temperature.

The engine temperature of the engine will affect the condition of the tensioner. If the engine is too hot, it could destroy the rubber belt and damage parts of the tensioner, causing it to fail. 

Periodically service the engine.

By serving your vehicle’s engine at the right time, every part of the engine is checked, including the timing belt tensioner. Any potential threat to the tensioner will be reviewed and fixed.

Check out for oil leaks.

The timing belt tensioner uses hydraulic oil to create pressure to maintain tension in the belt. When there is a leak in the hydraulic tensioner, the tensioner will lose pressure and be unable to maintain tension with the belt.

When periodically checking the tensioner, check for leaks also.

Change the timing belt when due.

You are expected to change the timing belt after every 60,000 to 100,000 miles, depending on your vehicle type. Check the vehicle’s manual to get the exact interval for the replacement.

Final Words

Whenever you hear a strange noise from the engine, try to find out the cause of the issue. The noise could be a result of a damaged timing belt tensioner. In such a situation, you should consider checking the timing belt and the tensioner. If you lack mechanical knowledge, you can have a professional diagnose and fix the issue appropriately.

Akindayini Temiloluwa

I am passionate about everything automotive. Right from when I got my first toy car as a kid, I developed an interest in the inner workings of vehicles. As I grew up, my love for mechanical stuff became more substantial enough for me to pursue a career in it. My goal as an automotive content writer is to simplify the most challenging concepts for my readers, help them self-diagnose what may be wrong with their vehicles and offer real value for their time.

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