What to Check When Buying a Used Car: The Full Guide

Most of a used-car check is available to anyone — it takes attention, daylight and about ninety minutes. Below is a 15-minute quick list and the full app-guided protocol we use ourselves: for every section, what to look at with your own eyes, plus honest notes on where equipment is unavoidable.

Check the history first, then inspect the car

Before travelling to the seller, compare the VIN, registration documents, IPO mileage records and any finance or legal restrictions. A history check can rule out a bad listing, but it cannot reveal a concealed repaint, stored fault codes or how the car drives. Those need an inspection at the car.

How to check a car’s history in Portugal →

The 15-minute quick check: top 10

VIN in the documents = VIN on the body and the plate (any mismatch — walk away)
Panel gaps and paint tone in daylight — unevenness betrays body repair
Glass markings on every window: the year should match; one “fresh” window deserves a question
Tyre DOT codes (week/year of manufacture) and even tread wear
Pedal, steering wheel and driver-seat wear — does it match the claimed mileage?
Oil filler cap: light “mayonnaise” emulsion is a head-gasket warning sign
Cold start: smoke colour, knocks or whistles in the first seconds
All the electrics in a row: windows, climate, multimedia, cameras, parking sensors
Test drive: pulling to one side, vibration at 80–120 km/h, how the gearbox shifts
IPO inspection history (the odometer is recorded at every test) and service records

Handy to take with you in print: Download the printable checklist

How to check up a car before purchase: step by step

The same order works for a do-it-yourself check and for a professional check-up of a car before buying — only the equipment changes.

Documents before you drive out. Ask for photos of the DUA and the last IPO certificate: match the VIN, year, owners and the mileage recorded at each inspection. A mismatch is a reason not to go.
Body in daylight. Panel gaps, paint shade, glass markings, tyre DOT codes. This is where the paint gauge earns its keep: a colour-matched respray is invisible to the eye.
Interior and electrics. Wear on the wheel, pedals and seat against the mileage; every button in turn; mats and the spare-wheel well for signs of water.
Cold start and under the bonnet. Smoke colour, unusual noises, emulsion under the oil cap, a suspiciously freshly washed engine bay.
A 20–30 minute test drive. Motorway and town: pulling to one side, vibration at 80–120 km/h, gearbox under load, braking with hands off the wheel.
Decision and negotiation. What you found is a list of arguments: price the repairs and negotiate from that figure, not from the asking price.

The full protocol: 210 points in 11 sections

Open a section — inside is the full point list plus tips on checking each area yourself.

Identity & documents

Match the VIN everywhere it appears: documents (DUA), body, plate. Ask for the IPO history — in Portugal the odometer is recorded at every inspection, the best free mileage-fraud detector.

VIN matches the registration card (livrete)
VIN on the body or behind the windscreen matches the registration card
Registration card (livrete) seen
Registration card data matches the vehicle
IPO valid (per document)
Import documents (DAV / COC / homologação) in order — Imported vehicles

Service history

The one section eyes cannot cover: factory paint is 80–160 µm, a respray is usually 160+. A colour-matched respray is invisible even to a trained eye without a gauge.

Timing drive
Engine oil
Gearbox oil
Last service
Keys
Service book and history

In a professional report this section is a table of readings for every panel — see the sample below.

Panels: paint and damage

Sight along the body against the light: orange peel, dust in the lacquer, runs. Open doors and bonnet — tool marks on bolts and hinges, sealant that isn't factory-shaped.

Front bumper — According to body type
Hood — According to body type
Front left fender — According to body type
A-pillar front, outer — left — According to body type
Front left door — According to body type
Left rocker — front half — According to body type
B-pillar middle, inner — left — According to body type
Rear left door — According to body type
Left sliding door — According to body type
Left rocker — rear half — According to body type
C-pillar rear, outer — left — According to body type
Rear left quarter — According to body type
Rear left side panel — According to body type
D-pillar (tailgate) left — According to body type
Pickup bed — According to body type
Trunk lid — According to body type
Tailgate — According to body type
Bed tailgate — According to body type
Rear bumper — According to body type
Rear right quarter — According to body type
Rear right side panel — According to body type
D-pillar (tailgate) right — According to body type
C-pillar rear, outer — right — According to body type
Rear right door — According to body type
Right sliding door — According to body type
Right rocker — rear half — According to body type
B-pillar middle, inner — right — According to body type
Front right door — According to body type
Right rocker — front half — According to body type
A-pillar front, outer — right — According to body type
Front right fender — According to body type
Roof — According to body type
Overcab/front mask — According to body type; motorhome body
Habitation wall left — According to body type; motorhome body
Habitation wall right — According to body type; motorhome body
Habitation rear wall — According to body type; motorhome body
Habitation roof — According to body type; motorhome body
Left skirt — According to body type; motorhome body
Right skirt — According to body type; motorhome body
Drawbar and front wall — According to body type; motorhome body

Body & paint

Headlights should carry the same markings and age evenly. Mismatched lights mean a replacement — ask why (accident?).

Panel gaps are even
Windscreen: chips and cracks in view zone
Glass markings consistent
Accessible structure (rails, welds, hinges)
Lights: haze, moisture, cracks, mounts

Tyres, wheels & brakes

Four matching tyres are the sign of a cared-for car. Mixed brands and years mean savings were made. The DOT code reads right off the sidewall.

Tyre brand, model and type — Per wheel, where accessible
Tyre size compared with registration data — Per wheel, where accessible
DOT manufacture date — Per wheel, where accessible
Tread condition and uneven wear — Per wheel, where accessible
Sidewall damage: cracks, cuts, bulges — Per wheel, where accessible
Rim damage and repair signs — Per wheel, where accessible
Brake disc: visible wear, scoring and cracks — Per wheel, where accessible
Visible brake pad condition — Per wheel, where accessible
CV boot: cracks, tears and grease leakage — Per wheel, where accessible

Under the hood

Your nose finds damp and mould faster than your eyes. Lift the mats, check the spare-wheel well — flood damage shows there first.

Engine oil level and condition — Combustion engine; according to drivetrain
Under the oil cap: no emulsion or sludge — Combustion engine; according to drivetrain
Coolant: level, colour, emulsion — Combustion engine; according to drivetrain
Brake fluid level
Oil leaks and sweating: valve cover, sump, seals — Combustion engine; according to drivetrain
Coolant leaks: radiator, hoses, expansion tank, water pump — Combustion engine; according to drivetrain
Other fluid leaks: brake, power steering, gearbox, fuel — Combustion engine; according to drivetrain
Smells and other seepage before start
12V battery: terminals, corrosion, age
Orange HV cables and connectors: no damage or signs of tampering — EV/hybrid
Accessory belts and hoses (accessible) — Combustion engine; according to drivetrain
Structure under hood: towers, rails, wing bolts
Chassis frame: rust and damage — SUV/pickup, if fitted and accessible
Front differential: leaks and rust — SUV/pickup, if fitted and accessible
Rear differential: leaks and rust — SUV/pickup, if fitted and accessible
Gearbox from below: leaks and rust — Combustion engine; according to drivetrain
Transfer case from below: leaks and rust — SUV/pickup, if fitted and accessible

Start & dashboard

Check with the engine cold: oil level and colour, emulsion under the cap, coolant level, signs of a freshly washed bay (a common way to hide leaks).

Engine was cold before start — Combustion engine; according to drivetrain
Starts on first attempt — Combustion engine; according to drivetrain
Warning lights: self-test OK, extinguish after start
READY mode engages, no HV warnings — EV/hybrid
Abnormal noises (cold/warm) — Combustion engine; according to drivetrain
Idle stability and vibration — Combustion engine; according to drivetrain
Exhaust: smoke colour at start — Combustion engine; according to drivetrain

Lights test

Start it yourself, from cold. Blue smoke — oil; thick white — coolant; black — fuelling. A knock or whistle in the first seconds calls for deeper diagnostics.

Low beam
High beam
Front indicators
Rear indicators
Hazard lights
Fog lights
Brake lights
Reverse lights
Plate lights
DRL

Interior

Even a cheap OBD dongle shows current faults. Stored faults, module mileages and live data need a proper scanner.

Steering wheel: rim wear, buttons
Driver's seat: bolster, upholstery, frame, adjustments
Instrument cluster and dashboard: condition, buttons, display
Pedals: pad wear
Selector / gear knob: wear, gaiter
Driver's door card: armrest, handle, switches, speaker
Window lifters: all doors, from driver panel
Locks: central locking, fob, all doors and boot
Mirrors: adjust, fold, heating
Front wipers and washer
Rear wiper and washer
Infotainment: screen, sound, radio, CarPlay
Cameras: reversing/surround view
Parking sensors: front and rear beep
USB / 12V / wireless charging
Climate: fan, zones, AC cooling, heater, smell
Horn works
Front passenger side: seat, glovebox, floor mat
Front-right door card
Headliner and trim: no sagging or stains
Sunroof/panorama: operation, blind, leak marks
Airbag covers: gaps, opening traces
Seat belts: condition, latching, tag date
Rear row: seats and floor
Rear door cards
Damp smell, moisture under mats and in boot
Boot: floor, spare well, trim — creases, welds, sealant
Kit: spare/repair kit, jack, triangle, vest

We read the modules with a Launch scanner and hand the client the full log — the sample report shows what that looks like.

OBD diagnostics

At least 20–30 minutes including highway: acceleration, braking with hands off the wheel, pulling, vibration at speed, gearbox behaviour under load.

Fault codes from accessible modules and scanner report
Available module mileage compared with the dashboard

Road test

Underbody, brakes from the inside, drivetrain leaks, suspension from below — physically impossible without a pit or a lift.

Insurance valid today (ASF/FGA or document)
Seller permitted the drive, route is safe
Shifting: jerks, delays, noises — Combustion engine; according to drivetrain
Acceleration without hesitation
Steering: tracking, pull, play
Vibration and noise at speed
Braking: efficiency, vibration, pull
Regenerative braking smooth; hybrid: engine starts/stops without shudder, EV mode holds — EV/hybrid
Suspension: knocks on bumps
Parking brake (EPB/handbrake) holds

This is a separate lift inspection: with us it is +€100 on top of the inspection, arranged in advance.

Post-drive check

No fresh leaks after the drive
Burning smell, fan operation, temperature
Hot restart: starts immediately — Combustion engine; according to drivetrain
No new warning lights after the drive

EV / hybrid — HV system

Displayed range and state of charge, % — EV/PHEV
Traction battery SOH, %
No BMS / HV system faults (active and stored)
Cell voltage spread within limits
HV insulation: no faults or warnings
Number of DC fast charges / total cycles — EV/PHEV
Charge port(s): flap, lock, contacts, cables — EV/PHEV
Charging test: charging starts, no errors — EV/PHEV
Charging kit: Mode 3 Type 2 cable, Mode 2 domestic cable, adapters — EV/PHEV
Traction battery and inverter cooling: coolant level, leaks, pump/fan
Heating and A/C in READY, according to the model’s intended operation
Battery casing: impacts, dents and leaks in accessible areas
Documented battery warranty terms: duration and mileage
Battery ownership or lease documents, where applicable — EV/PHEV

Habitation

Roof and body seams: sealant, cracks
Windows and rooflights: panes, seals, stays, screens
Damp: corners, under windows, lockers — smell, soft panels
Floor: delamination, creaks — walk the full length
Awning: roll-out, fabric, lock, legs
Entry door, fly screen, step
Pop-top roof: mechanism, canvas, zips — Campervan/converted van
Gas locker: bottle strap, drop-out vent
Gas regulator and hoses: date, condition, odour
Hob: all burners, flame-failure device holds
Heater (Truma/diesel): start-up, warm air
Boiler: heats water (gas/230 V)
Leisure battery: type and capacity (AGM/gel/LiFePO4, Ah)
Battery under load: no voltage sag
Solar panel: mounts, glass, cable gland
Charge controller (MPPT/PWM): charging in daylight
Alternator charging (DC-DC): current with engine on
Shore power 230 V: lead, charger indicator
Inverter 230 V: powers the sockets
All-zone lighting, 12 V/USB sockets
Control panel: water/charge readings sane
Fresh tank: filling, cap, smell
Pump and taps: pressure everywhere, dry under sinks
Kitchen and washroom sinks: drains, traps
Shower: tray, doors/curtain, head, drain
Cassette toilet: blade, flush, cassette and seal
Grey tank: drain valve, smell
Fridge is cold (switched on in advance!)
Beds and slats: intact, lift mechanisms
Lockers, tables, hinges, catches: secured for driving
Belts and mounts of travel seats

Lift inspection

Brake hoses, pipes and cables: cracks, corrosion, leaks
Inner CV boots and driveshaft seals: splits, grease throw-out, leaks
Tie rods, track-rod ends and steering rack: play, rack boots, PAS leaks
Ball joints, control arms and rear beam/trailing arms: play, boots, deformation
Control-arm, rear-beam and subframe bushes: cracks, extrusion
Dampers and springs: leaks, broken coil, corrosion
Anti-roll bars: drop links, bushes
Wheel bearings: play and noise with the wheel off the ground
Underbody and sills from below: corrosion, deformation, impact marks
Subframes and chassis rails: fasteners, corrosion, repair welds
Sump guard/underbody shields and aero panels: integrity, fasteners
Engine/gearbox mounts (EV: drive-unit mounts): torn rubber, sag, hydraulic mount leaks
Leaks from below: engine, gearbox, axles, seals — Combustion engine; according to drivetrain
Exhaust system: integrity, hangers, catalyst/DPF present — Combustion engine; according to drivetrain
Fuel lines and tank: corrosion, leaks, tank straps — Combustion engine; according to drivetrain
LPG tank and lines: mounting, corrosion, multivalve, test date — LPG
Propshaft, differential, transfer case: leaks, U-joints, centre bearing — Combustion engine; according to drivetrain
Traction battery from below: casing, shield, fasteners, signs of opening or repair — EV/PHEV
HV cables and connectors under the floor: orange conduit, insulation, fasteners — EV/hybrid
Traction battery cooling circuit: pipes, radiator, leaks — EV/PHEV
E-motor and reducer (AWD: both units): oil leaks, driveshaft seals, mounts — EV

📄 What this looks like in a professional report

So you have something to compare against: download an anonymised sample of a real report — paint readings per panel, findings, verdict and photos. Free, and useful even for a fully DIY check.

Download the sample report (PDF)

When to call a professional

The honest criterion is not “always” — it is these situations:

The car is in another city — the trip and a day off cost more than the check
No paint gauge and no scanner — the two key sections stay blind
An expensive car: the cost of a mistake is many times the cost of a check
The seller is rushing you (“three more people are coming”) — classic pressure
You don't speak Portuguese and the seller speaks nothing else

Mobile check-up — €150 How the inspection works

Can you properly check a car without any tools?

About seventy percent of it, yes: documents, gaps, glass, tyres, interior, start-up, test drive. Two zones stay blind: paint (a colour-matched respray only shows on a gauge) and electronics (stored faults and module mileages need a scanner).

How long does a DIY check take?

The full protocol takes 1.5–2 hours. Short on time? Run the top-10 from this guide in 15–20 minutes — it filters the most expensive problems: crash-repaired bodywork and clocked mileage.

What tools should I bring?

A torch, a cloth, gloves and the printed checklist as a minimum. Ideally: a paint-depth gauge (from €30–40) and an OBD dongle (from €20). The famous magnet trick does not work — modern panels are often aluminium or plastic.

What should I check first if I have almost no time?

Five things: VIN match, glass markings, tyre DOT codes, emulsion under the oil cap and how the car behaves on a test drive. Those five minutes filter out most of the dangerous cars.

Isn't a valid IPO (Portuguese MOT) proof of condition?

No. The IPO checks minimum safety requirements — brakes, lights, emissions. Paint, crash repairs, engine and gearbox condition are not part of it: a car with a fresh IPO can still be a rebuilt wreck.

Checked it yourself and still in doubt?

Send the listing link on WhatsApp — we'll tell you honestly whether the car deserves attention, and come out with the gauge and scanner if needed.

WhatsApp +351 308 812 536