“It only does it sometimes” is useful information. The next step is to describe what happened and the circumstances, without turning a guess into a diagnosis. A short record can give a mechanic a clearer starting point when the symptom is absent at the appointment.
You do not need to identify the failed part before booking. The AA's fault-finding FAQs explicitly include noises that happen only sometimes and advise discussing them at the appointment. A written history supports that conversation; it cannot guarantee that a fault will be reproduced or found.
Put safety before collecting a symptom history
If a problem affects braking or steering, or involves smoke, a suspected fuel leak, overheating or immediate danger, concentrate on stopping safely and getting appropriate assistance. Follow the vehicle handbook and the advice of qualified help. Do not make another journey or repeat a manoeuvre just to collect evidence.
The Highway Code's breakdown guidance explains places of relative safety and the additional precautions for motorways. A roadside breakdown is not the place to carry out a photo session or attempt repairs for this log.
Write notes, use an app or take photographs only when safely parked and it is safe to do so. GOV.UK's phone guidance explains that holding and using a device while driving is prohibited, including taking photos or videos. Waiting at traffic lights is not a safe opportunity to fill in the log.
What should you record when the problem comes and goes?
After the event, write down what you remember. Use “unknown” or “not noticed” instead of filling gaps with assumptions. Approximate times and durations are fine when labelled as estimates.
- Vehicle and date
- Make, model, year, engine if known, approximate mileage, and when the event happened.
- The actual symptom
- What you heard, felt, saw or smelled. Keep “a rattle” separate from “a faulty timing chain”, which is a proposed explanation.
- What the vehicle was doing
- Starting, idling, accelerating, braking or turning; whether it had been standing or had already been driven. Record only what you recall.
- Pattern and duration
- How long it lasted, how often it has happened and whether it stopped on its own. Note relevant weather or recent work without assuming they caused it.
- Warnings and effect
- The exact dashboard wording or light if known, steady or flashing, and any change in how the vehicle behaved.
- Action and existing evidence
- What you did next, any professional advice received, and relevant existing photos, recordings or reports.
The editable text worksheet needs no account or email address. It is a place to keep observations, not an instruction to continue driving until you have enough entries.
A clearer description without guessing the cause
Fictional example · illustrative observations
Initial description: “The engine sometimes makes a noise.”
Useful record: “2016 Ford Focus, petrol, about 78,000 miles. On Tuesday morning, while parked, I heard a metallic rattle for roughly two seconds on the first start after the car had stood overnight. I could not identify where it came from. I did not notice a warning message. It has happened on two mornings this week, but I have not recorded every start.”
Question for the garage: “What information would help you investigate this, and how should I arrange for the vehicle to be assessed?”
This does not identify a failed component or establish that the vehicle is safe. “I did not notice a warning” is also different from a checked statement that no warning appeared. Keep those uncertainties in the handover.
Keep recordings and diagnostic reports in context
If you already have a safely obtained photo or recording, retain the original and note which event it belongs to. Sound alone may not reveal its source. Avoid sharing unrelated faces, addresses, messages or personal information with a public forum.
Include an existing garage or diagnostic report with its date, vehicle and findings. Do not turn a code description into a confirmed repair instruction. For the difference between symptom discussion and reading vehicle data, see our guide to AI car diagnosis without an OBD scanner.
Do not clear codes, disconnect the battery or change components just to make the record look different. Snap-on's scanner guidance warns that clearing codes can erase diagnostic information and advises recording it first. Ask the investigating professional before altering the vehicle or its stored diagnostic information.
Give the garage a brief history and an open question
Send a short summary first, with the log available if requested. Say when the symptom began, whether it is changing, any recent work and what has already been checked. Separate your observations from previous advice and internet suggestions.
- Does this need urgent assessment, and what is the appropriate way to get the vehicle to you?
- Would you prefer a written log, an existing report or the original recording?
- What investigation is proposed, what will it cost and what needs approval before extra work?
- If the symptom is absent, what can you check and what should I report next?
Let the garage decide what checks or controlled tests are appropriate. A symptom disappearing at an appointment does not explain its cause, and a log is not a substitute for inspection.
Use HoodHero to organise the conversation
When safely parked, you can describe the vehicle and your observations to JAX in HoodHero, then answer its follow-up questions. No OBD adapter is needed for that conversation. The worksheet above can help you prepare the details; it is a separate text file, not an automatic vehicle recording or monitoring feature.
JAX can help explore possible explanations and next questions, but it cannot physically inspect the vehicle, confirm a failed part from this history or certify that driving is safe. See HoodHero for drivers for the mobile features. Download is free; the main diagnostic and repair features require a paid membership, with prices and terms shown in the app.
Sources checked 6 November 2026: AA Mobile Mechanic FAQs, the Highway Code's breakdown guidance, GOV.UK phone-use guidance and Snap-on scanner documentation. The record format, fictional example and garage questions are original practical aids.
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