Every vehicle with a combustion engine requires a properly timed combustion reaction to function. That means pistons need to rise and fall in the cylinders at the exact right time, valves need to open and close to allow exhaust gases and air in, and fuel needs to be injected at the exact right moment to mix with air in the proper amounts so that the spark can ignite them. Everything is time to down to a fraction of a second to make sure your engine is functioning properly. In most engines this is maintained by the timing belt.
A timing belt connects a gear at the end of your camshaft to another gear at the end of the crankshaft. As the crankshaft spins, the pistons rise in the cylinders and then the combustion reaction forces them back down again. At the same time the camshaft is turning which opens the valves to allow the pistons to enter. If this reaction isn't taking place precisely right, you'll suffer all kinds of different problems up to and including your total engine failure depending on how bad it is.
Subaru vehicles function the same as vehicles made by other manufacturers in this regard. Your Subaru engine needs to have either a timing belt or a timing chain in order to synchronize all the parts in this precisely timed system.
Do Subarus Have a Timing Belt or a Timing Chain?
The timing belt looks like a pretty typical rubber drive belt that you might find in any number of systems. A timing chain on the other hand looks much more like a bicycle chain. It's clearly made of metal with linkages and it's much more heavy duty. Both of them perform the same function however, it's just that a timing chain is clearly built to be stronger and last longer.
For many years timing gears and timing chains were standard in all vehicle engines. After the oil crisis and when manufacturers were looking at ways to cut costs in producing vehicles, timing belts started becoming standard fare. Although timing belts are strong, they are not as strong as a timing chain so they're subject to wearing down and breaking more frequently. But they were a lot cheaper to produce for a time as well, and lighter as well.
These days many manufacturers are moving back towards the timing chain as a standard device under the hood of cars. Timing chains are sturdier, they last longer, and tend to be more reliable. Higher end vehicles often choose timing chains rather than timing belts but sometimes it's hard to know what your vehicle has inside of it. Your owner's manual should be able to tell you, and you could also Google the make and model of your vehicle to figure it out for yourself as well.
When it comes to Subarus nearly all Subaru vehicles made since the year 2013 are equipped with timing chains. The exception here is the Subaru WRX and the Subaru WRX STI. These are higher performance models and they both had timing belts stick around a little bit longer than other models. The WRX kept timing belts under the hood until 2014 before switching to chains. The WRX STI however continues to use timing belts.
If you are wondering why, it's because the WRX STI is a high-performance vehicle with an engine that is typically under more stress than your average Subaru. The result of that is the process of replacing a timing belt is easier than replacing the timing chain. But that's only because of the stress of a high-performance engine. It makes more sense for a standard type of engine to use a chain when possible because of how durable they are.
When Should a Timing Belt be Replaced on a Subaru?
If you have an older model of a Subaru that still uses a timing belt, then your owner's manual should have the maintenance schedule including a guide to let you know when you need to have your timing belt inspected. For instance, Subaru recommends that the timing belt in the Legacy get an inspection every 30000 miles. That's just an inspection, and they recommend a replacement every 105,000 miles.
The recommended change time for a timing belt on a Subaru is actually pretty impressive compared to most other models of vehicles. Depending on what other kind of car we're talking about, the scheduled maintenance for a timing belt is usually between 60,000 miles and 100,000 miles. So, the 105,000 miles for a Subaru is very much at the high end of the scale. Again, though it's worth remembering that you need to check the manual because this can change from one Subaru model to another.
When it comes to timing chains, these are actually designed to last the life of the vehicle in theory. That means that you should get well over 200,000 miles out of a timing chain. It's possible a timing chain can last for much longer than that as well. Theoretically, a timing chain should last indefinitely unless some problem arises that causes it to fail.
What Happens if the Timing Belt Breaks on a Subaru?
When the timing belt breaks, the kind of engine you have has a very big impact on what is going to happen next. An interference engine versus a non-interference engine is what we're talking about here. In an interference engine when the timing belt breaks the camshaft and the crankshaft are no longer synchronized. The camshaft will stop spinning but the crankshaft will not. That means that the camshaft is not able to open and close the valves properly any longer so they will remain in whichever position they were in when the belt stopped working. The crankshaft, because it's still spinning, will cause the pistons to rise up in the cylinder. This is where the problem comes in.
If the valves are closed because the camshaft isn't functioning any longer the pistons may crash into the valves and cause a lot of damage. This could destroy your engine entirely. Even in the best-case scenario you're going to have some serious damage and your car will stop working right away. The reaction is pretty much instantaneous and there's not much that you can do about it once it happens. The name interference comes from the fact that the piston can interfere with the valve if they come in contact with each other.
In a non-interference engine, the pistons don't rise to the level of the valves in the cylinder. That means we're in the timing belt breaks, you will not suffer the same serious damage as a result.
Subaru has used both interference engines and non-interference engines over the years. Older model Subarus, those made in the mid-90s and earlier may be non-interference engines. However, anything made more recently is probably an interference engine. The reason Subaru uses its interference engine, even though it could lead to the serious kind of damage which can cost many thousands of dollars to repair, is that the compression ratio in an interference engine is much better than a non-interference engine. In other terms, an interference engine gives you better engine performance than a non-interference engine. The trade-off is that you have the risk of contact between the valves and pistons.
In general, Subarus that were made in 1996 and before are non-interference engines. Afterwards you're more likely to have an interference engine.
When the piston hits the valves in an interference engine of a Subaru, the damage it causes can be to the cylinders themselves, the valves, the pistons, the cylinder heads and more. Often these repairs could start at $1,000 and potentially get up to $4,000 or more.
For these reasons it's important that you follow that schedule of maintenance and inspection for your timing belt. If you regularly inspect your timing belt, you shouldn't be caught by surprise when it wears down and ideally that will mean it's not going to fail unexpectedly on you and cause this kind of severe engine damage.
How Much Does It Cost to Replace a Timing Belt on a Subaru?
When it comes time to replace the timing belt in your Subaru you can expect a cost in the neighbourhood of perhaps $650 to $900. Compared to some vehicles that's actually pretty reasonable. The cost of replacing timing belts across all vehicle models on average ranges from $500 on the low end up to over $2,000 and some vehicles.
The reason that the cost of replacing the timing belt is so high is that it's a fairly involved repair job. It takes some effort to get into a vehicle’s engine deep enough to get their timing belt out, so the labour cost is really where most of the fees are coming from.
A timing belt itself from AutoZone, just for the part, can range in price from $50 for an after-market version up to over $350 just for the belt itself. It really depends on the kind of Subaru you're driving of course and how old it is. It's definitely hard to get original parts for older model vehicles these days.
Signs and Symptoms of a Bad Timing Belt
When your timing belt starts to go wrong there are a few indications it’s going to give you a heads up. As we said, some Subarus can keep their timing belts for over 100,000 miles. But there's a reason they ask you to inspect every 30,000 miles. Timing belts can wear out and fail on you before their time. If you notice any of these symptoms, you should give your timing belt another inspection.
There are many issues in a vehicle that can cause unusual noises, but if you're noticing a repetitive, fast-paced ticking noise from the engine of your Subaru it's a good chance if the timing belt. As the timing belt begins to break down the teeth on the inside can break off and as it rotates between the camshaft and a crankshaft gear it can produce a ticking sound. The sound is not unlike a fast spinning roulette wheel in some vehicles.
Engine Won't Turn Over
If your timing belt has broken, first count yourself lucky that it happened when you weren't behind the wheel. The second thing you'll notice is that your engine simply won't start at all if the timing belt is not in place. That's because the camshaft and crankshaft aren't connected at all and your engine simply can't start as you try to start your car. The starter motor will try to start your vehicle and you will hear that, but that's as far as it will get.
When the teeth come loose from the timing belt not only will you potentially hear that ticking sound, but it may also cause some rough idling as well. Rough idling is best described as a shaking or vibrating sensation when you're just sitting in your vehicle as though the engine is simply struggling to run.
Because the timing belt keeps your camshaft and your crankshaft perfectly synchronized, if it starts to stretch out or lose teeth it will not be performing at 100% any longer, that synchronisation is going to suffer as a result. That can lead to engine misfires because everything is not precisely aligned any longer. The air and fuel mixture into your combustion chamber may be injected at the wrong time or in the wrong ratio for the spark to occur, which can make it so that the combustion reaction simply doesn't happen in one of your cylinders or it happens at the wrong time. That is an engine misfire and if it happens frequently enough it can cause damage in your engine.
Bad Oil Pressure
It's possible you can suffer an oil leak if the timing belt cover gaskets get worn out. Likewise, if enough teeth break off your timing belt so they can fall into the oil pan and clog it up. That will prevent the oil from circulating through your engine, which in turn can lead to your engine overheating and your oil pressure going down.
The Bottom Line
As we said, most modern Subarus rely on a timing chain these days which is a lot more reliable and durable than a timing belt. Either one of these can fail though and both of them require routine inspections just in case. That said, the cost of replacing a timing belt can be quite high so you want to make sure you keep track of yours because the cost of repairs when something goes wrong can be even higher.