Timing belts and timing chains

Timing belt

A timing belt is a scheduled replacement item. The correct interval can include both mileage and age, and differs by engine. On many interference engines, belt failure can allow pistons and valves to collide, causing severe internal damage.

A proper replacement normally uses the correct kit, including the belt, tensioner and guide rollers. The water pump and auxiliary-drive components are assessed according to the engine design and condition.

Timing chain

A chain is lubricated by engine oil and may not have one universal replacement interval. It can nevertheless wear, stretch or develop tensioner and guide problems. Correct oil specification, oil level and regular oil changes are important to hydraulic tensioner and chain life.

Possible warning signs

• Rattle at cold start or persistent timing-area noise.
• Camshaft/crankshaft correlation fault codes.
• Difficult starting, rough running or reduced power.
• Known belt interval reached with no proof of replacement.
• Oil or coolant contamination near the belt area.

Before the work is agreed

CD-EX confirms the exact engine, required parts, known interval and scope of work. If the service history is uncertain, written evidence is more reliable than an assumption that the belt was replaced.