Diagnosis by sound starts in the conversation, not in the workshop. The mechanic has not been sitting in your car for the last two weeks and knows exactly as much about the problem as you manage to tell him. “Something knocks in there” narrows nothing at all. “A dry knock, front right, on small expansion joints, only when the car is cold” narrows it to three parts. Here is what a useful description is made of, and which wording works best.
The five things a mechanic needs
Character. Not “a noise” but a specific type: a knock, a creak, a squeal, a hum, a click, a crunch, a tick, a rattle. Pick the word by feel: a knock is a single impact, a rattle is a rapid drumming, a hum is a steady low background.
Location. Front or rear, left or right, underneath or under the bonnet. Even a rough direction cuts out half of the possible parts. If you feel it through your hands on the steering wheel, say so separately.
When it appears. Cold or warm, over bumps or on smooth tarmac, in a corner, under braking, under acceleration, at idle. This is the single most important item on the list.
What it follows. What changes the sound: speed, engine revs, load, temperature, a pedal. The difference between “it follows road speed” and “it follows engine revs” moves the search from the chassis to the engine and back.
How it has changed. When it started and what it has done since: appeared a week ago and is getting worse, or has been the same for six months. A fast-growing noise is always more worrying than a stable one.
Wording that works
| Weak | Strong |
|---|---|
| “The suspension knocks” | “A dry knock, front right, on small joints, at 20–40 km/h” |
| “A wheel is humming” | “A steady hum from 60 km/h, louder when I change lanes to the left, still there when coasting” |
| “Something ticks in the engine” | “Ticking from the top for the first 40 seconds after a night out, then it goes” |
| “The brakes squeal” | “A squeal under light braking at low speed, gone when I brake hard” |
| “It jerks when accelerating” | “A jolt shifting from second to third, started a month ago” |
The right-hand column is not workshop jargon; it is ordinary words in the right order: what, where, when, what it follows. You do not need to know the terminology — and a wrong term does more harm than no term at all, because it sends the mechanic down a false trail.
Common mistakes
The first is bringing a diagnosis instead of a symptom. “My timing chain has stretched” sounds confident, but if the theory came from the internet, the whole visit will revolve around it. Even when the theory is right, it belongs after the facts.
The second is exaggeration. “A terrible din” and “an awful howl” measure nothing. A comparison is far more useful: louder than the radio at half volume, audible only with the window down, audible to passengers in the back as well.
The third is leaving out the history. Recent repairs, a hit against a kerb, a trip down a rough track, a change of tyres — all of it changes the list of theories.
The fourth is describing from memory instead of recording. A sound is far easier to show than to describe: the phone is always in your pocket, and a recording removes half the misunderstanding.
How to structure the conversation
A working formula is three sentences and a recording. First: character, location, conditions. Second: what the sound follows and when it started. Third: what has already been done to the car. Then play the recording and let the mechanic listen.
After that, ask a question back: “what will you check, and in what order?” A clear answer is a good sign; a vague “we’ll see as we go” is a reason to be careful. When the diagnosis is done, ask to be shown the finding on the car rather than told about it in words. If the noise is in the engine, it is worth looking through the catalogue on the symptom page knocking in the engine beforehand.
One more thing worth knowing: a workshop that cannot reproduce a noise should say so plainly instead of replacing parts on suspicion. “We did not manage to reproduce it, come back when it is constant” is an honest answer and a cheaper one than a list of speculative jobs.
If putting all this together on the spot is awkward, the Pro-Stuk app asks exactly these questions in order and puts the answers together with the recording into a single card: character, location, conditions, what it follows, and the likely causes with percentages. Showing that card to the mechanic is enough — the description is already written.
