Timing Belt vs Timing Chain: What's the Difference?

Written by Petro Olekhnovych, mobile mechanic in Aylesham, Kent

A timing belt and a timing chain do the same job: they keep the top and bottom halves of your engine turning in step. The difference in the timing belt vs timing chain question is what they are made of and how they are looked after. A belt is reinforced rubber and must be replaced at the interval in your handbook, while a chain is metal, runs in engine oil and is generally designed to last much longer.

What a timing belt or chain actually does

Your engine has a crankshaft at the bottom, turned by the pistons. At the top, a camshaft opens and closes the valves. Haynes explains that the timing belt or chain links the two, so the valves open at exactly the right moment for each piston.

If that link slips or breaks, the timing is lost. Depending on the engine, that can mean it simply stops, or it can mean serious internal damage. More on that below.

Timing belt: how it works and how long it lasts

A timing belt is a toothed, reinforced rubber belt. Haynes notes that belts became popular in the 1970s and 1980s partly because they need no lubrication.

Belts are light and quiet, but rubber wears and deteriorates with time and use. That is why every belt has a replacement interval set by the manufacturer. Start Rescue says this is likely to be at least 60,000 miles, and perhaps up to 100,000 miles on a newer model. Intervals vary a lot between cars, so always check your handbook or service book, including whether it gives a time limit as well as a mileage.

On many engines the belt also drives other parts. Start Rescue says that, depending on the model, it may drive the water pump, oil pump and injection pump. Because getting to the belt is labour-intensive, it often makes sense to replace the water pump at the same time. Tensioners and idler pulleys may also need replacing. Our post on timing belt replacement in Kent goes into the job itself.

Some engines use a belt that runs in oil, often called a wet belt. We cover those in our post on wet timing belts.

Timing chain: how it works and how long it lasts

A timing chain is made of metal and, unlike a dry belt, needs lubrication from the engine oil. Haynes says chains have come back into fashion over the past couple of decades because of their greater robustness and longer life expectancy.

Fast Car says a chain generally lasts the life of the engine, as long as it has proper lubrication and regular oil changes. That condition matters. A chain relies on clean oil at the right level, so skipping oil changes is a bad idea on a chain engine.

Chains are not maintenance-free forever. Haynes explains that a chain can stretch slightly over time. That can make the engine run poorly, and a worn chain can make a rattling noise. Fast Car also notes chains are generally more expensive to replace if they do wear out.

Timing belt vs timing chain at a glance

What happens if a belt or chain fails?

Haynes says timing belts tend to snap without much warning. That is the big risk: there is often no noise or warning light before it goes.

What happens next depends on the engine design. Start Rescue explains that in an “interference” engine, the valves and pistons can collide when the belt breaks, which is likely to cause serious engine damage. On an older car, the repair can cost more than the car is worth. In a “non-interference” engine, the engine will usually just stop and not restart.

If your engine cuts out suddenly and will not restart, or you hear a new rattle or knocking from the engine, stop driving. Get it checked before going any further.

How to tell which one your car has

The simplest way is to look in your handbook or service book. If your car has a belt, the service schedule will list a timing belt or cambelt change at a set mileage or age. If it has a chain, there is usually no scheduled replacement.

If you do not have the handbook, a mechanic can tell you from your make, model and engine.

If you have bought a belt-driven car and there is no proof the belt has been changed, it is safest to treat it as due. Replacing the belt on schedule makes far more sense than waiting for it to fail. See our guide to timing belt replacement cost for what affects the price.

How we can help

We are a mobile mechanic based in Aylesham, so we come to you at home or work. We cover Canterbury, Dover, Deal, Sandwich, Folkestone and the villages around them. You can book an appointment or message us on WhatsApp.

We replace timing belts (cambelts) and water pumps, and we can check your service history to tell you whether your car is due. If you hear a rattle or the engine is not running right, we can come out, diagnose the cause and tell you what it needs. Labour is £30-£50 per hour depending on the job, parts are extra, and the price is agreed on WhatsApp before we start.

Frequently asked questions

Is a timing chain better than a timing belt?
Neither is simply better. Chains generally last longer, but rely on good oil changes. Belts are quiet and light, but must be replaced on schedule.

Do timing chains ever need replacing?
They are generally designed to last the life of the engine, but they can stretch over time. A rattle from the engine is a reason to get it checked.

How often should a timing belt be changed?
It depends on the car. Check your handbook or service book for your car’s interval and stick to it.

Should I change the water pump with the timing belt?
Often, yes, on engines where the belt drives the pump. The labour overlaps, so doing both together usually makes sense. Read more about water pump failure symptoms.

Need help? Send a WhatsApp to 07563 350335 with your car’s make and model and we’ll come to you.

Sources

• Timing belts vs timing chains: what are the key differences? (Haynes)
• Timing belt vs timing chain (Fast Car)
• When should a timing belt be replaced? (Start Rescue)