How Often Should My Timing Belt Be Replaced?

When it comes to major engine services, timing belt replacements are one of the most important. Neglecting a timing belt service can lead to catastrophic issues, including engine failure. In this article, we will discuss what a timing belt does, why it’s important, and how often you should have it replaced on your vehicle.

What is engine timing?

Before we talk about the timing belt itself, let’s go over engine timing. Your engine is divided into two main parts, the bottom end, and the cylinder head. These parts are connected with head studs or bolts and are sealed with a head gasket.

The bottom end of an engine contains the rotating assembly, including the crankshaft, connecting rods, and pistons. Moving parts also use bearings, which aid in reducing friction between metal components. The rotating assembly transfers the power generated by the engine to the transmission, and eventually to the wheels.

Close up of timing belt

The cylinder head is where the valvetrain, ignition, and fueling system live. The valvetrain contains the camshaft(s), valves, valve springs, and associated hardware. The fuel rail, injectors, and sparkplugs (gasoline only) are housed in the cylinder head. These parts work together to control the intake of air and fuel, the timing of combustion, and the expulsion of exhaust gases.

Engine timing keeps the cylinder head rotating with the bottom end, ensuring proper engine operation. Adjustments in timing can impact fuel economy, performance, and other aspects of engine operation, but that is a topic for a separate article. Correct timing is essential to engine function.

What is a Timing Belt, and What Does It Do?

The rotating parts in both the cylinder head and bottom end of the engine need to operate very precisely. This is where the timing belt comes in. The belt connects the bottom end to the cylinder head, ensuring both parts of the engine are in precise time with the other.

Graphic displaying routing of timing belt

What are Timing Belts Made From?

Most timing belts are made of a reinforced, high-density rubber composite. Some belts use neoprene, polyurethane, or even Kevlar to increase strength and resilience. In addition to the forces generated by the engine, timing belts need to resist extreme heat, weather, and exposure to harmful fluids like oil, gas and diesel, and coolant.  

Why Do Timing Belts Fail? 

Timing belt failure is usually attributed to age and poor maintenance. Even on a well-maintained car, an old belt will still succumb to weakening, stretching, and cracking. A belt that has prolonged exposure to fluids can also weaken. A compromised belt is much more likely to fail catastrophically.

What Happens When a Timing Belt Fails?

The outcome of a timing belt failure will depend on if you have an Interference or Non-Interference engine you have in your car.

The pistons and valves cross paths on an interference engine in the combustion chamber. When the engine is in time, the movement of the valves and pistons occurs in a way that prevents them from making contact. When the timing belt breaks or fails, the timing will be off, meaning the pistons and valves will most likely contact each other. Depending on the engine rpm and severity of the contact, the valves will bend or break. This will normally require a cylinder head replacement and in some cases an entirely new engine.

Non-Interference engines do not have the same risk of catastrophic failure. The valves and pistons never cross paths. If a timing belt failure occurs, the car will simply stop running as the camshaft(s) will no longer be operating the valves. Once the belt is replaced and the engine is re-timed, it will run as it did before with little other work needed.

It’s worth noting that the vast majority of vehicles on the road today, particularly those made in the last 15 or so years, utilize interference engines due to performance and fuel efficiency benefits.

bent valve from broken timing belt
A bent valve resulting from a failed timing belt.

How often should I get my timing belt replaced?

Timing belt replacement is a major service and can be pretty expensive, well over $1000 in most cases. Luckily, timing belts can last a long time. If you take care of your vehicle, you should plan on doing a timing belt replacement every 90,000-100,000 miles. Between these intervals, the belt should be checked periodically to ensure no significant wear has taken place.

Despite being expensive, a timing belt service will always be cheaper than replacing a cylinder head or entire engine. The long intervals between replacements give owners time to prepare for the cost, and knowing you have a new belt means you can confidently drive without fear of it breaking.

Gates timing belt kit

Timing Belt Replacement at Becker Service Center

If your car is due for a timing belt replacement, schedule an appointment with Becker Service Center. Our Naperville repair shop is staffed with ASE-Certified technicians with the knowledge and skills to service your car. Submit an appointment form or give us a call to schedule today!