When to replace common wear parts
Some parts warn you before they fail; others simply have a service life and should be changed on schedule. Knowing which is which saves money — and, with a couple of these, saves the engine.
Timing belt — by schedule, not symptoms
A cambelt is the one to never leave. On an interference engine a snapped belt lets the valves and pistons meet, and the repair costs more than the car. Change it by the manufacturer's mileage or age interval, whichever comes first, and do the water pump at the same time if it's belt-driven. Don't wait for a noise — by then it may be too late.
Brakes — pads then discs
Pads wear faster than discs; you'll often get through two sets of pads to one set of discs. Warning signs are squealing, a grinding feel, vibration through the pedal, or a lip you can feel on the disc edge. Replace discs and pads together when the discs are near their minimum thickness, and bed new brakes in gently.
Battery — around five years
Most car batteries last four to six years. Slow cranking, dashboard flicker on start, or a car that struggles after a cold night are the usual tells. Stop/start cars use specific AGM or EFB batteries — fit the right type, not just the right size.
Suspension — in pairs
Shock absorbers and springs wear gradually, so the decline is easy to miss. A floaty or bouncy ride, knocking over bumps, uneven tyre wear or nose-dive under braking all point to tired dampers. Replace them in axle pairs so the car sits and handles evenly.
Glow plugs and coil packs — the ignition wear items
Diesels rely on glow plugs for cold starting; hard starting on a cold morning and a glow-plug light are the signs. Petrols rely on coil packs; a misfire, a flashing engine light or a rough idle usually points to one failing. Both are relatively cheap and often a DIY job.