Used car inspection checklist: under the hood and underneath

Why it matters

The walkaround tells you what the car has been through. Mismatched panel gaps or paint texture can indicate repaired accident damage. Under the hood, the oil, the coolant and the rubber parts show whether maintenance has been kept up, and the ground under a parked car shows whether anything leaks.

What to look for

• A panel gap that feels different from the same gap on the other side: that panel has likely been off the car
• Paint texture that doesn't match between panels
• Rust in the wheel arches, door bottoms, sills and underside
• Fresh undercoating, which can sometimes be used to hide rust or leaks
• Fluid drips, or fresh stains on the ground after the car has been parked a few minutes
• Very dark, gritty oil on the dipstick, which can suggest overdue maintenance
• Residue around the hoses and radiator suggesting coolant leaks
• A white or bluish crust on the battery terminals
• Cracking or fraying on the belts and visible hoses
• Water stains, a mold smell or a musty odor under carpets and seats, which can indicate flood damage

Step by step

1. Walk around the car in daylight and run a finger along the gaps between the hood, fenders and doors, comparing both sides.
2. Check the wheel arches, door bottoms and sills. Press gently on any rust: a soft spot is structural.
3. With a flashlight, look under the car for rust, fresh undercoating and drips.
4. On a cold engine and level ground, check the oil level and color on the dipstick, and the coolant level.
5. Look at the battery terminals, the belts and the visible hoses.
6. Test all doors, windows, locks and the trunk, and check under the carpets and seats for water stains or a musty smell.
7. Once the car has stood for a few minutes, look at the ground underneath for fresh fluid stains.

What you find, and what it can mean

• A dark drip under the car: oil.
• A green or pink drip, or a colored puddle under the front: usually coolant. The color depends on the coolant type.
• Surface rust or surface bloom: cosmetic.
• Flaking layers, a soft spot, or rust through: structural, the one fault that can write a car off.
• Panel gaps or paint that don't match: not an automatic deal-breaker, but get a mechanic's opinion.
• Water stains or a musty smell under the carpets: can indicate flood damage.
• Dark oil on the dipstick: can suggest overdue maintenance, but oil naturally darkens with use, so ask for the service receipts as well.

What people get wrong

Inspecting only in the dark or in the rain. Damage, rust and paint mismatches are much harder to spot in poor light or wet conditions. Always view and inspect the car in daylight, and bring someone else along when you meet a private seller.

When to get a professional inspection

Walking around the car and checking fluids is reasonable for most buyers to do themselves, but it is a first-pass check to decide whether the car is worth a professional look. Many serious issues aren't visible without a lift and the right tools, so any car you are seriously considering deserves a pre-purchase inspection from an independent mechanic, not one recommended only by the seller.

Read next

• Car losing coolant: where is it going?
• Car burning oil: how to tell and what it means
• Used car test drive checklist: what to check on the road

This page is general information and does not replace a professional assessment. Symbols, codes and behaviour vary between makes. Always check the handbook for your own car.