Used Car Inspection Checklist: What to Check Before You Buy

A pre-purchase inspection (PPI) at a mechanic costs $100–$150. It's money well spent — but only if you don't know what to look for yourself. With this checklist, you can do a thorough DIY inspection before deciding whether to hire a mechanic for confirmation or walk away entirely. Many serious problems are visible to anyone who knows where to look.

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What You'll Need

• OBD2 scanner (many auto parts stores will lend you one, or buy a $25–$40 Bluetooth unit)
• Flashlight
• Paper towel or white rag
• Phone (to look up VIN history)
• Magnet (to check for body filler on metal panels)
• This checklist

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Before You See the Car

Run a VIN check. Use CarFax or the free NHTSA database (vpic.nhtsa.dot.gov) to check for accident history, title issues, and odometer discrepancies. Pay attention to the number of prior owners and whether the car was a rental, lease, or fleet vehicle.

Search for TSBs and recalls. The NHTSA recall database (nhtsa.gov/recalls) lists every open recall by VIN for free. If a recall exists, ask the seller when it was addressed.

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Exterior: What to Check Before You Get In

Body panels and paint:

• Look down each side of the car at a low angle (eye level with the roofline). Waves or ripples in the panel surface indicate prior collision repair.
• Run a magnet along the lower panels, doors, and quarter panels. If the magnet doesn't stick strongly, there's body filler underneath — indicating previous damage.
• Check panel gaps: the space between the hood and fenders, door and frame should be even. Uneven gaps indicate misaligned panels from a collision or poor repair.
• Check for overspray: paint on rubber trim, window seals, or chrome indicates a repaint.

Glass:

• Check for cracks or chips in the windshield. A chip can be filled for $50; a full crack means replacement ($200–$600).

Tires:

• Check the wear pattern. Even wear = good. Edge wear only = alignment issue or over/underinflation. Cupped or scalloped wear = worn shocks/struts.
• Check the date codes on the tires. The last four digits of the DOT number tell you the week and year of manufacture (e.g., 3219 = 32nd week of 2019). Tires over 6 years old should be replaced regardless of tread depth.

Underneath the car:

• Look for rust. Surface rust on the frame is cosmetic; pitting or flaking rust that penetrates the metal is structural. Check especially on the frame rails, subframe mounting points, and floor pan.
• Look for oil leaks: fresh oil on the oil pan, transmission, or differential indicates active leaks.
• Check the exhaust. Heavy black soot at the tailpipe tip = oil burning. Blue-tinged soot = oil consumption.

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Under the Hood

Oil dipstick:

• Pull and wipe clean, re-insert, pull again. The oil level should be between MIN and MAX.
• Look at the color: dark brown/black is normal. Milky, gray, or foamy oil indicates coolant mixing with oil — a blown head gasket flag.
• Smell it. A burnt smell indicates an overheat event in the car's history.

Coolant reservoir:

• The level should be between MIN and MAX.
• Look at the color: green, orange, or pink is normal depending on the coolant type. Rusty or brown coolant indicates neglected maintenance.
• A milky film on the coolant reservoir cap can indicate head gasket issues.

Power steering fluid:

• Check the level on the reservoir or dipstick. Low PSF can indicate a leak; dark brown or black fluid indicates neglect.

Transmission fluid (if accessible dipstick):

• Should be pink to red. Brown or burned-smelling ATF indicates heat damage.

Belts and hoses:

• Squeeze the radiator hoses. They should be firm but pliable. Soft, mushy, or cracked hoses are due for replacement.
• Check the serpentine belt for cracks, fraying, or glazing.

Battery:

• Look for corrosion on the terminals (white or blue-green buildup). Heavy corrosion indicates a leaking battery or neglect.
• If possible, test voltage with a multimeter. A fully charged battery should read 12.6V+.

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OBD2 Scan: The Most Important Step

Plug your OBD2 scanner into the port (usually under the dash on the driver's side) with the ignition in the ON position. Check for:

Active codes (DTCs): Any stored P, U, B, or C codes indicate a current problem. Write them down and research what they mean.

Readiness monitors: Check the emissions readiness monitors. If multiple monitors show "NOT READY," the seller may have recently cleared codes to hide check engine lights. Not all monitors reset quickly — if 3+ are not ready on a car that supposedly "runs fine," that's a red flag.

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The Test Drive

• Cold start: Start the car from cold. Any rattling, tapping, or knocking on cold start that disappears when warm indicates worn engine components (timing chain, cam followers).
• Acceleration: Listen for hesitation, surging, or unusual noise under hard acceleration.
• Braking: Apply brakes firmly at 40 mph. The car should stop in a straight line without pulling. Listen for grinding, squealing, or pulsation.
• Steering: The car should track straight at highway speed without correction. Note any vibration in the wheel.
• Transmission shifts: Automatic — shifts should be smooth and timely. Any slipping, hard shifts, or delayed engagement is a transmission red flag.

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Red Flags Summary Table

What You Find	What It Means
Milky oil or coolant	Head gasket failure (expensive)
Body filler on structural panels	Major collision repair
Multiple NOT READY OBD monitors	Codes recently cleared
Active OBD fault codes	Known problem being hidden
Cupped tire wear	Worn shocks/struts
Rust on frame rails	Structural integrity concern
Uneven panel gaps	Prior collision, poor repair
Blue smoke from exhaust	Oil burning — engine wear
Transmission slipping	Costly repair or replacement needed

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Related Guides

• Car Repair Cost Guide: What You Should Actually Pay
• 5 Signs Your Mechanic is Ripping You Off
• 10 Cheapest Ways to Fix Your Car Yourself

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