Usually a top-end issue — sticking hydraulic lifter, low oil level, worn camshaft, or an exhaust manifold gasket leak that sounds metallic on cold start.
Here's a quick, honest answer from a working UK mechanic — what causes it, what it costs to fix, and what to do next.
First check
Always check the oil level. A car a litre low can develop ticking lifters within minutes of starting. Top up with the correct grade and listen again — many ticks vanish.
Manifold gasket leak
If the tick is loudest from cold and fades as the engine warms, you likely have a blowing exhaust manifold gasket or cracked manifold. £180–£500 to fix depending on car.
Lifters and cams
Persistent ticking from the top of the engine after a proper oil top-up suggests a sticking lifter or wear. An oil change with a flush often helps; if not, deeper investigation is needed.
Is ticking serious? — Sometimes yes. A persistent metallic tick can mean valve train wear that turns into bigger damage if ignored.
Could it be an injector? — Yes — diesels normally tick from injectors. A loud knock from one cylinder means a failing injector that needs urgent attention.
More detail on: Why does my engine make a ticking noise?
The short answer above covers the usual case. Below is the extra detail a UK driver normally needs to act on it — how to narrow the fault down, what it should cost, and when it is worth paying a garage rather than carrying on. This is general guidance from a working mechanic, not a substitute for someone putting your own car on a ramp.
Pin down when the noise happens
Noises get misdiagnosed because nobody narrows them down properly. Work through it methodically: does it change with road speed or engine speed? Does it appear only under braking, only on turns one way, only when cold, or only over bumps? A rumble that rises with road speed and disappears when you load the opposite wheel on a roundabout is a wheel bearing. A squeal that vanishes the moment you touch the brake pedal is usually the pad wear indicator. A knock over bumps at low speed is suspension, not drivetrain.
What it usually is not
Most drivers arrive convinced a noise is the gearbox or the engine internals, and most of the time it is something on the outside of the car that costs a fraction of what they feared — a heat shield, a worn drop link, a dry CV joint or a stone trapped in a brake shield. Have the cheap and common causes eliminated before you authorise anything that involves removing a gearbox.
Safe to keep driving?
Treat anything affecting brakes, steering, tyres, seat belts or visibility as stop-now, no matter how well the car appears to be driving. Overheating and low oil pressure are also stop-now: the damage curve on both is measured in minutes, not miles. Most other faults will let you drive gently to a garage, but if the car is in limp mode, losing fluid, or the fault changes how it steers or stops, get it recovered instead. Recovery is cheaper than a tow plus a new engine.
What Bob would check first
Start with the cheap, common and visible: fluid levels and their condition, tyre pressures and wear pattern, battery voltage and terminal condition, and every connector and vacuum pipe in the area of the fault. A surprising share of electrical gremlins are a corroded earth or a chafed loom, and a surprising share of running faults are an air leak downstream of the sensor doing the complaining. Only after that does anything get unbolted.
When it is worth going to a main dealer
Three situations justify main-dealer money: an open safety recall (free), a live manufacturer warranty or goodwill claim, and coding or programming work that needs manufacturer-level software. Everything else — servicing, brakes, suspension, clutches, cambelts, diagnostics — an experienced independent will do to the same standard for a good deal less, and using an independent does not invalidate your warranty under UK block exemption rules as long as the correct parts and schedule are used.
Get an answer on your own car
If you want this looked at properly for your exact vehicle, send the details and Bob will write back — make, model, engine, mileage, when the fault happens and any codes you have. You get a written reply from a qualified UK mechanic with 32 years on the tools, not a chatbot, and your money back if he cannot help.
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