What Is a Cambelt?
The cambelt (also called a timing belt) is a reinforced rubber belt with teeth that synchronises the rotation of the crankshaft and the camshaft(s). This synchronisation ensures that the engine's intake and exhaust valves open and close at precisely the right moment relative to the pistons.
If the cambelt slips or breaks, the valves and pistons move out of sync. On interference engines (the majority of modern engines, including most Toyotas, Hondas, and Subarus sold in NZ), the valves and pistons will physically collide — bending the valves and potentially destroying the engine.
This makes the cambelt one of the most critical maintenance items on any vehicle that has one.
Cambelt vs. Timing Chain
Not all vehicles have a cambelt — some use a metal timing chain instead. Chains are generally designed to last the life of the engine (though they do wear and can stretch).
Key difference: A timing chain is metal and doesn't have a fixed replacement interval. A rubber cambelt degrades with heat and age and must be replaced on schedule regardless of whether it looks worn.
Common NZ vehicles that use a cambelt include:
- Toyota Corolla (older 1ZZ, 4AFE engines)
- Honda Jazz, Civic, HR-V (many models)
- Subaru Impreza, Forester (older DOHC models)
- Mazda 3, 6 (some models)
Common NZ vehicles with a timing chain (no cambelt):
- Toyota Corolla (newer 2ZR engine)
- Mazda Demio (SkyActiv engines)
- Subaru BRZ/Toyota 86
- Most modern turbocharged engines
If you're not sure which your vehicle has — ask your mechanic or check your owner's manual.
When to Replace the Cambelt
The replacement interval varies by manufacturer, but most NZ vehicles specify:
- Every 100,000 km or 10 years (whichever comes first) — common for most Japanese brands
- Every 60,000–80,000 km — some older Honda and some European vehicles
- Always at 10 years — rubber degrades with age, even if kilometres are low
The "whichever comes first" is critical. Many NZ drivers with low-mileage vehicles assume their cambelt is fine because they haven't driven far. But a 15-year-old cambelt on a car with 50,000 km is past due regardless of the mileage — the rubber has hardened and cracked with age.
What's Replaced at the Same Time?
A cambelt service almost always includes replacing the tensioner, idler pulleys, and often the water pump (which is driven by the cambelt on many engines). Replacing these at the same time is standard practice because:
- Labour to access the cambelt is the same regardless
- A failed tensioner will destroy a new belt immediately
- Water pump failure (also driven by the belt) soon after a cambelt change is a warranty nightmare
What Happens If the Cambelt Breaks?
On an interference engine, a broken cambelt causes immediate, severe engine damage:
- Bent or broken valves (almost certain)
- Damaged valve guides or seats
- Possible piston damage
- Possible cylinder head damage
Engine repair or replacement after cambelt failure typically costs $4,000–$12,000+ in New Zealand. In many cases, the vehicle is written off. The cambelt replacement that would have prevented this costs $500–$1,200.
NZ Cost to Replace a Cambelt
| Service | Typical NZ Cost |
|---|---|
| Cambelt only (simple 4-cylinder) | $400–$700 |
| Cambelt + tensioner + idler | $550–$900 |
| Cambelt + tensioner + water pump | $650–$1,200 |
| 6-cylinder engines (more complex) | $900–$1,800+ |
Prices depend heavily on parts cost and access. Subaru DOHC cambelts are more labour-intensive than a simple Toyota SOHC, for example.
WoF and the Cambelt
A WoF inspector is not required to check the cambelt service history, and they cannot see the belt without disassembly. However, many responsible mechanics will note an overdue cambelt during a WoF inspection as a safety advisory. An engine destroyed by a snapped belt will fail the owner far more than a WoF ever would.
When to Book a Mechanic
- Your vehicle's cambelt is due by age (over 8–10 years) or mileage (over 100,000 km)
- You've bought a second-hand vehicle and have no service history
- Your mechanic has recommended replacement
- You can see or hear anything unusual from the engine timing area
If in doubt, assume it's due. The cost of a cambelt service is trivial compared to the cost of a failed engine.