Pre-Purchase Inspection Checklist 2025: What Mechanics Check Before You Buy

Why Pre-Purchase Inspections Matter

A pre-purchase inspection (PPI) is the most important step in buying any used vehicle. For $100-$200, a qualified mechanic examines the car on a lift, identifies current problems and upcoming maintenance needs, and gives you the information to make an informed decision.

Studies show over 60% of used vehicles have undisclosed problems ranging from minor (worn brakes, tired tires) to major (transmission issues, hidden damage). The inspection cost is trivial compared to discovering these problems after purchase.

What Mechanics Inspect

Engine and Drivetrain

• Oil condition: Color, level, presence of coolant or metal particles
• Coolant condition: Level, color, signs of oil contamination
• Compression test: Cylinder health and sealing (if warranted)
• Leak inspection: Oil, coolant, transmission fluid, power steering
• Belt and hose condition: Cracking, age, tension
• Engine mounts: Condition and wear
• Timing components: Belt/chain condition, service history
• Exhaust system: Leaks, catalytic converter condition

Transmission and Clutch

• Fluid condition: Color, smell, level (burnt smell = problems)
• Shift quality: Smoothness, hesitation, slipping
• Clutch (manual): Engagement point, slippage, chatter
• CV joints/axles: Boot condition, clicking when turning
• Differential fluid: Level and condition (AWD/4WD vehicles)
• Transfer case: Operation, fluid condition (AWD/4WD)

Suspension and Steering

• Struts/shocks: Leaking, bounce test, worn bushings
• Ball joints: Play, wear, safety
• Tie rod ends: Play, wear, boot condition
• Control arm bushings: Cracking, wear
• Wheel bearings: Noise, play
• Power steering: Pump noise, fluid condition, leaks
• Alignment: Uneven tire wear indicating issues

Brakes

• Pad/shoe thickness: Remaining life percentage
• Rotor condition: Thickness, scoring, warping
• Caliper function: Sticking, leaking, slide condition
• Brake lines: Rust, corrosion, leaks
• Brake fluid: Level, color, contamination
• Parking brake: Adjustment, function
• ABS function: Warning lights, operation

Body and Frame

• Frame inspection: Damage, repairs, rust perforation
• Unibody rails: Straightness, weld marks indicating repair
• Panel gaps: Inconsistency indicating repair or damage
• Paint inspection: Overspray, texture differences, blend lines
• Undercarriage rust: Surface vs. structural corrosion
• Floor pans: Rust perforation, water damage
• Door hinges: Sag, wear, operation

Electrical Systems

• Battery test: Load test, age, terminal condition
• Alternator output: Charging voltage and amperage
• Starter function: Cranking speed, noise
• All lights: Headlights, signals, brake lights, interior
• Power accessories: Windows, locks, mirrors, seats
• HVAC system: Heat, A/C, fan speeds, blend doors
• OBD-II scan: Current and pending codes, readiness monitors

The OBD-II Scan

A critical part of any inspection is plugging into the OBD-II diagnostic port. This reveals:

• Current codes: Active problems triggering check engine light
• Pending codes: Developing issues not yet triggering lights
• History codes: Previously cleared codes (some systems store these)
• Readiness monitors: Shows if codes were recently cleared

If all monitors show "not ready," the battery was recently disconnected or codes were cleared—ask why. This could indicate hidden problems.

Red Flags That Should Stop a Purchase

• Frame damage: Any evidence of frame or unibody repair
• Transmission problems: Slipping, harsh shifts, burnt fluid
• Major engine issues: Timing chain noise, head gasket symptoms
• Flood damage signs: Musty smell, water lines, sediment
• Odometer tampering: Inconsistent wear patterns, suspect history
• Multiple cleared codes: Hiding known problems
• Structural rust: Perforation of frame or unibody

Using Results to Negotiate

Most inspections find some issues—that's expected on used cars. Use findings strategically:

1. Get repair cost estimates from the inspecting shop
2. Categorize: immediate needs vs. upcoming maintenance
3. Present findings to seller with documentation
4. Request price reduction equal to immediate repair costs
5. Factor maintenance items into your budget

Reasonable sellers expect negotiation based on inspection findings. Sellers who refuse to negotiate after legitimate issues are found may not be worth dealing with.