That squealing or chirping sound coming from under your hood when you first turn the key may mean you’re dealing with a not-so-good timing belt tensioner. This small, yet very important engine part keeps the timing belt tensioned for optimal camshaft and crankshaft synchronization.
In this article, we will talk about the common symptoms of a bad tensioner that indicate a replacement is needed, and what the cost will be to accomplish the replacement.
What is a Timing Belt Tensioner?
In simpler terms, a timing belt tensioner is a device that keeps the timing belt at the proper tension for accurate timing of the camshafts and crankshaft.
Specifically, a timing belt tensioner:
- Takes up slack in the timing belt and keeps a constant belt tension when various components heat up and cool down. If there is slack in the belt, the engine may run poorly (or stall).
- Compensates for the normal wear and stretch of the timing belt over time. This is important since proper tension is needed to ensure accurate valve timing.
- Absorbs shocks from the timing belt and isolates the timing belt from the other components in the timing system to prevent damage and enhance belt life.
Timing belt tensioners create tension using either a spring-loaded arm or hydraulic pressure that acts against the timing belt to counteract loosening or slackening.
This allows it to keep the timing belt at a relatively constant tension to synchronize the opening and closing of the intake and exhaust valves with the piston movements.
Valve timing can get thrown off if the timing belt tensioner is not functioning in the proper manner, which can have damaging consequences.
Top 6 Bad Timing Belt Tensioner Symptoms
Here are 5 common symptoms that indicate the timing belt tensioner has failed. Any combination of these is an indicator that you likely need to replace your tensioner.
#1. Squealing Noise.
Squealing or chirping noise from the timing belt area can indicate a problem with the timing belt tensioner.
When a timing belt tensioner is beginning to wear out and loses its ability to sufficiently apply tension on the timing belt, it can make noise as the belt is slapping or rubbing on other components in the system.
This happens when the tensioner can no longer take up slack and absorb shocks in the belt as it was designed to do.
With a failing tensioner, the noise may be louder or happen more frequently within the first few seconds after starting the vehicle from cold due to the expansion of numerous engine components and their need for time to stabilize to normal operating conditions.
A worn tensioner will have a lot more variation in timing belt tension at colder temperatures during initial startup when the engine components need to warm to stabilize their levels of expansion, respectively, which in turn affects the overall belt tension.
A squealing or chirping sound may also occur intermittently or only under certain loads or RPMs as the tension in the belt varies more from a lack of damping.
In some cases, the timing belt cover can be removed to rule out if the noise is radiating in the general area of the tensioner pulley.
Although the presence of a squeal or chirp alone does not mean the tensioner needs replacing, it is definitely a warning sign that the components in the timing system should be inspected for additional problems or potential damage to the engine.
#2. Check Engine Light.
If the timing belt is loose due to a faulty tensioner, the timing of the valves will be off. This denotes problems with the engine, resulting in the check engine light coming on in the dashboard.
Since the check engine light can mean a million different things, you can have it scanned for trouble codes via a car scanner, which can confirm the issue.
#3. Knocking Sounds.
A loose timing belt will knock around and hit the timing cover and other parts inside it. That said, it may not sound like knocking; it could be more of a slapping sound. You should not confuse this sound with a rod knock.
#4. Engine Fails to Turn Over.
A loose timing belt resulting from a bad tensioner will cause the camshaft and crankshaft to disengage from each other. This means you won’t be able to ignite the fuel and air mixture from inside the chamber.
When you turn the key in the ignition, you may hear the motor, but you still will not be able to turn the engine over.
#5. Grinding Sounds.
A loose timing belt will not have a firm grip to spin the pulleys and will create a grinding or rattling noise from the pulleys themselves, especially if a pulley bearing is bad.
#6. Engine Misfires.
Premature opening or closing of the cylinder valve will result in an engine misfire. This denotes that the timing belt could not rotate both the camshaft and crankshaft together.
Timing Belt Tensioner Replacement Cost
The cost to replace a timing belt tensioner can be as little as $150 or as much as $500. The parts alone can be as low as $60 up to $350, depending on your vehicle, and whether the tensioner is OEM or aftermarket.
Labor will generally cost between $90 – $150. Taxes and fees will likely be added to these charges.
How Long Does a Timing Belt Tensioner Last?
Unlike the timing belt itself, the tensioner will not have a manufacturer-suggested timing belt change interval.
In almost all cases, you must also change the timing belt tensioner at the same time you have the timing belt replaced, which is generally between 75,000 and 100,000 miles.
The actual life expectancy of the tensioner is by far longer than the timing belt itself but because it is usually quite hard to gain access to the timing belt tensioner, you will save yourself quite a bit of money in the long run replacing the tensioner (and the water pump if you need to) when you do a timing belt change.