The short version: define the question, preserve the history and record what the vehicle can actually prove.
Build a dated timeline
Record the purchase date, mileage at purchase, when each symptom appeared, who was contacted, when the vehicle was examined and what repairs were authorised. Keep the wording factual. Include periods when the vehicle was unavailable and note any relevant warning messages exactly as displayed.
Keep the original documents
Save the advert, order form, invoice, finance or warranty agreement, inspection sheets, recovery records, job cards, diagnostic reports and receipts. Export important messages or emails rather than relying only on a phone screenshot. Keep originals and provide copies when asked.
Record the vehicle without changing it
Photograph warning messages, visible leaks or damage, mileage and relevant components where safe. Do not clear fault codes, replace parts or dismantle the vehicle simply to create evidence. Safety comes first: stop using the vehicle and seek recovery if continued driving could be unsafe or cause damage.
Define the technical question
Examples include: is the reported fault currently present; does the evidence support the repair said to have been completed; and what further tests are reasonably required? A narrow, answerable question produces a more useful report than asking an assessor to prove that somebody is at fault.
Common questions
Before you arrange an inspection
Should I clear the warning light before inspection?
No. Stored codes, freeze-frame information and warning messages may be relevant evidence. Leave them intact unless a safety-critical repair requires immediate action.
Can screenshots replace invoices and diagnostic reports?
They can support the timeline, but original documents and complete reports normally provide better context than cropped images.
Do I need legal advice?
Engine Clean provides technical inspection and reporting, not legal advice. Citizens Advice or an appropriate dispute-resolution service can explain consumer options.
Independent guidance
For consumer rights or dispute procedure, use the appropriate independent service:
Citizens Advice: problems with a used car