If you’ve ever bought a used vehicle, you’ve probably heard of a timing belt. Many people say you should know when the the timing belt was last replaced before you purchase an older vehicle.
Unlike a serpentine belt, a timing belt is not visible when you pop the hood. However, there are still ways you can tell when it’s time to change out this critical engine belt.
What Does a Timing Belt Do?
The function of the timing belt is to rotate the crankshaft and camshaft of the engine and to make sure they’re synchronized in their rotation. This synchronization allows the cylinders to fire at the right time and keep the engine running the way it is supposed to.
If the timing belt were to break or become worn out, you could be stranded with an inoperable vehicle. Extensive engine damage often occurs when a timing belt snaps.
Since the timing belt in the engine is constantly subjected to stress and harsh conditions, it’s critical to follow the car manufacturer’s recommended timing belt change interval.
Top 5 Bad Timing Belt Symptoms
When you have a worn, cracked, torn, or broken timing belt, there will be some obvious signs that will show up. Below are five of the most common symptoms of a bad timing belt that you should watch out for.
As soon as you suspect a failing timing belt, you should have your car towed to a repair shop to avoid the chance of completely breaking the belt (if it hasn’t already fallen off its pulley).
1) Engine Stalls
If your timing belt snaps or slips off a pulley, your engine will stall. Without a timing belt, the valves don’t open and close at the right time (if they move at all).
Although the engine may have the capability of firing the injectors and the spark plugs, there is no way to suck in air and expel air at the precise time it is necessary.
2) Rough Idling
Are you experiencing rough idling from your engine? If so, then you may be experiencing lots of jerkiness and shakiness as you’re behind the wheel. This is one of the main symptoms of a faulty timing belt.
If your timing belt has worn out or missing teeth, then it will likely slip out of its position, skipping one or more teeth on the belt. The engine timing will then be off, resulting in a very rough idle or a stall.
3) Broken Valves or Pistons
Whenever there is no synchronization between the rotating crankshaft and camshaft, the piston could get damaged and end up bending the valves as it comes in contact with them. The most common reason for this happening is when the timing belt totally snaps apart.
The only thing you can do at this point is to install a new timing belt before the engine gets seriously damaged (if that hasn’t already occurred).
4) Low Oil Pressure
As a timing belt starts to get excessive wear, pieces of its teeth will come loose and break off into the oil pan of the vehicle. This will cause a significant drop in the oil pressure of the engine.
If not enough lubrication gets to the internals of the engine, complete engine failure may occur. At that point, rebuilding or replacing the engine is the only fix.
5) Ticking Sound
The timing belt is connected to lots of pulleys and is surrounded by a lot of other components. If the timing belt wears out, it may start to become loose and possibly make a ticking sound as it continues to deteriorate.
The sound will remain there until it’s replaced, or the timing belt gets so worn that it breaks apart.
How Long Does a Timing Belt Last?
Timing belts typically last 60,000-100,000 miles, depending on the vehicle and how it is driven.
If you’ve recently purchased a vehicle and you don’t know when this maintenance was last performed, you should strongly consider replacing the timing belt.
Causes of Timing Belt Failure
The number one cause of a failed timing belt is age. If you wait too long to replace a timing belt trying to stretch out its useful life, you are likely to end up with a more expensive repair than if you just replaced the timing belt in the first place.
2) Poor Quality Timing Belt
There are many reputable brands of timing belts that can fit a given vehicle. Lower quality belts may have a reduced service life over the OEM specification. Poor quality control may also be a factor.
If you buy an aftermarket timing belt, make sure you are buying the correct belt for your vehicle. You will also want to check that the timing belt manufacturer is reputable and carries a good reputation. Some brands are better for certain vehicles than others.
3) Bad Tensioner
If your timing belt tensioner fails or is not adjusted properly, this can cause premature timing belt failure.
When the belt is too tight, this could also prematurely wear your idler pulleys or water pump. If your water pump fails, you may experience overheating issues, in addition to problems with engine timing.
What Happens If a Timing Belt Breaks?
In a Non-Interference Engine
A non-interference engine means it is not possible for the valves or pistons to contact each other, no matter which position the crankshaft or camshafts are in. This is true with or without a timing belt attached to the engine.
If a timing belt snaps or slips off your non-interference engine, the worst thing that will happen is the engine will stall. You will be stranded wherever you’re at, unable to start the engine until the timing belt is replaced.
While it’s never a good thing to be stranded, the good news is you will not experience any significant damage to the engine from a snapped timing belt. The worst you might see is some light scuffing on the inside of the timing covers as the belt spins freely. This does not alter the performance of the engine once the timing belt is replaced.
In an Interference Engine
An interference engine means there is a possible engine position where a valve can contact a valve, or a piston can contact a piston. This of course can only happen if the timing belt is not attached to the engine.
If you snap a timing belt on an interference engine, it is extremely likely that you will experience significant engine damage. You could end up with a bent valve, a scored piston, or a damaged valve seat.
Most damage of this nature will not be visible until the engine is disassembled. You may be able to confirm the damage by sticking a borescope down the spark plug hole.
There is a very small chance you could escape with no damage if the engine happens to die in precisely the right position. It’s certainly a gamble, and not one you should risk. Repairing internal engine damage will easily cost thousands of dollars.
Timing Belt Replacement Cost
When you realize that it’s time to replace your timing belt, the total cost will likely put a dent in your wallet. Because a timing belt job usually includes replacing the water pump, belt tensioner, and idler rollers (in addition to the belt itself), the total replacement cost will be between $800 and $1,100 on average.
The price will be on the lower end for small vehicles and on the upper end for larger trucks and SUVs. Expect to pay more at a dealership vs a good independent mechanic.
While the timing belt kit itself will only cost about $100 to $150, additional parts like the water pump will add another $200 or so. Timing belts are usually purchased in kits that contain the idler pulley(s) and a replacement tensioner. Some even come with the water pump.
See Also: Average Timing Chain Replacement Cost
The biggest expense will the for the labor costs since replacing a timing belt can take a few hours. For this reason, plan on about $600 to $800 just in labor costs. Unless you have at least a moderate amount of auto repair experience, you shouldn’t try to replace a timing belt yourself. This is one of those jobs you should let a pro handle.