Sparesbox Blog

5 Symptoms of a Bad or Failing Timing Belt

By Linda Quan

Fri Jan 17 2020

The timing belt plays a crucial role in the performance and functioning of an engine. The belt acts as a link between the crankshaft and the camshaft to control synchronized opening and closings of the valves, allowing for smooth operation. Considering its importance and the enormous duress the timing belt works under, regularly replacing the belt is crucial a healthy timing system and engine.

A functioning timing belt should be regularly maintained per the OE vehicle recommendations. Made from rubber, quality timing belts are durable, withhold incredible strength, and perform best under pressure. For the average car owner, it can be easy to tick over your km’s without realizing you’ve passed your service interval.

However, allowing a functioning timing belt to forgo routine maintenance can make for an expensive trip to the mechanics. Once a timing belt has worn out and snaps, the engine will no longer function. If a timing belt breaks while driving in an interference engine, the camshaft will stop turning, leaving some of the valves in the open position. The heavier crankshaft will continue to rotate, moving pistons up and down. This will cause the pistons to hit the open valves, which can result in heavy damage to the engine valves, pistons and cylinder head and block.


If the timing belt fails while driving in a non-interference engine, the damage will be less extensive. Nevertheless, having a timing belt snap and the engine stall on you can easily be avoided with preventative timing belt maintenance.

Neglecting regular maintenance, including the replacement of your timing belt, can lead to complete engine replacement. Repairing an improperly maintained vehicle timing system, or one that has experienced damage due to timing belt failure, can potentially set you back thousands of dollars.

With this in mind, it’s important to take note of your belt replacement intervals. Routinely replacing your belt will ensure your vehicle is safe from avoidable engine damage. Another key to a healthy timing system is recognising the signs of a wearing timing belt. Sparesbox have put together a list of symptoms of timing belt in need of a replacement. If you notice any of these warning signs, be sure to get in touch with your local mechanic as soon as possible to avoid belt failure.



1: Engine Won’t Start  

If your engine is struggling to turn over, something is obviously not right. There are a multitude of issues that could be the cause and identifying the part responsible can be difficult. One way to determine the problem is to listen out for the starter motor. If you can still hear the starter motor when the ignition is on, even if the engine won’t turn over, the problem may very well be the timing belt.

A wearing timing belt can slip and cause the cylinders in your car’s engine to open and close out of synchronisation. The engines timing falls out of calibration, causing the engine to misfire and fail to turn over. If you do suspect your timing belt is causing a failing engine, have it replaced immediately by your local mechanic before it does any more damage.


2: Engine Is Making Strange Noises

While a timing belt works to create a healthy timing system between two halves of the engine, you should not be able to hear anything to do with timing. Any strange ticking or alike noises should be treated with caution.

Outdated and worn timing belts are known to make noises upon starting the engine, accelerating, and idling. You shouldn’t be able to hear any strange noises from your engine, and if you do, it’s time to take your vehicle to the mechanic.

Something else to be wary of is engine vibration. If your engine begins to vibrate differently than it normally would, this may also be an indication of a required timing belt replacement.


3: Engine Running Erratically

Another warning sign of a worn-out timing belt is when you notice the engine running rough. This may be present in the form of it shaking, bouncing when idling, screeching/whirring, loss of power, or inconsistent RPM counts.

The timing belt is made up of little “teeth” grips that grab on to gears as it rotates the moving parts of the engine. If the teeth become worn, break, or fall off, the car will compensate by slipping gears, leading to failure and stalling of your engine.

Another possibility is that your timing belt is “jumping a tooth”, causing the car to suffer from loss of power. This can make for a rough feeling engine, with strange idling bounces and possibly a flashing check engine light. If your engine’s natural rhythm is being significantly disturbed, consider having your timing belt checked and replaced.


4: Check Engine Light

If your vehicle begins to flash the ‘check engine’ light, then chances are, there’s something wrong with your engine. Generally speaking, a timing belt failure is a pretty common cause of your engine being in trouble.

If the engine light has begun flashing because of the timing belt, it’s likely that the belt has become loose, slipped, missed a tooth or is failing. All of these are strong indications of a timing belt that is in dire need of a replacement. Ignoring these signs can lead to a broken timing belt, which can ultimately lead to a damaged engine and a very expensive mechanic bill.


5: Engine Exhaust Fumes & Smoke

If you’ve noticed your car is releasing unusually large amounts of exhaust fumes or smoke, this may be another indication that your timing belt is overdue a replacement. A worn-out timing belt will overwork the engine, causing excessive exhaust fumes.

When your car starts pouring out thick smoke from the tailpipe, the fuel isn’t burning properly. This is likely due a worn timing belt, and the valves not opening or closing in time. The best course of action from here is to have a professional identify the problem and check on the condition of the timing belt.


If you recognise at least one of these five symptoms of a failing timing belt, it’s time to take your car to your local mechanic. If your car is suffering from a worn timing belt, catching the problem early is not only going to save your engine, but also thousands of dollars.

Preventing timing belt failure is simple with routine maintenance per the manufacturer’s recommendations. Taking care of your timing belt will ensure your engine is not put in any avoidable danger. It’s important to remember - preventative maintenance will always end up being less expensive than mandatory maintenance.