How To Shop For A Used Car

Shopping for a Used Car: A Technical Guide for the Discerning Buyer

So, you're in the market for a used car? Excellent! Buying used can be a fantastic way to save money, but it also requires a more discerning eye than buying new. This isn't just about kicking the tires (though that's a good start). This article is designed to equip you, the experienced DIYer, with the knowledge to inspect a used vehicle with a critical and technically informed perspective. We'll cover key aspects of the inspection process, focusing on identifying potential problems before they become your problems.

Purpose: Why this Matters

Why go to all this trouble? Simply put, a thorough pre-purchase inspection can save you thousands of dollars in future repairs. It allows you to negotiate a better price, or, more importantly, walk away from a potential money pit. Knowing the vehicle's condition empowers you. You can assess the true cost of ownership beyond the sticker price, factoring in immediate and potential maintenance needs. This knowledge also provides a baseline for future maintenance and modifications.

Key Specs and Main Inspection Areas

We'll break down the inspection into several key areas, each with its own critical specifications to consider:

Engine: This is the heart of the machine. We'll be looking for signs of wear, leaks, and improper maintenance. Key specs include compression ratio (though testing requires specialized tools), oil pressure (if available via a gauge), and the presence of any abnormal noises.
Transmission: Automatic or manual, the transmission is crucial for smooth operation. We'll assess shift quality, fluid condition, and any signs of slipping or hesitation. Key specs include gear ratios (important for performance enthusiasts) and the presence of a torque converter (in automatics).
Suspension and Steering: These systems dictate handling and ride comfort. We'll look for worn bushings, leaking shocks, and play in the steering components. Key specs include spring rates (for those considering modifications) and steering gear ratio (for steering responsiveness).
Brakes: Safety first! We'll examine brake pad thickness, rotor condition, and brake fluid quality. Key specs include rotor diameter and brake pad friction coefficient.
Electrical System: Modern cars rely heavily on electronics. We'll check battery health, alternator output, and the functionality of various systems. Key specs include battery cold cranking amps (CCA) and alternator amperage output.
Body and Frame: Structural integrity is paramount. We'll look for signs of rust, damage, and previous repairs. Pay close attention to areas that are likely to corrode, like rocker panels and wheel wells.

The Inspection Process: A Step-by-Step Guide

1. Gather Your Tools

Before you head out, assemble a basic toolkit:

Flashlight: For peering into dark corners.
Tire pressure gauge: Ensuring proper inflation.
OBD-II scanner: Reading diagnostic trouble codes (DTCs). Crucially important for identifying potential issues.
Jack and jack stands: For safely lifting the vehicle. Never work under a vehicle supported only by a jack!
Gloves: Keeping your hands clean.
Rags: For wiping away grime.
Note pad and pen: For recording your observations.
Magnet: to check for body filler
Small mirror: to check hard to see places.

2. Initial Assessment: Walkaround and Documentation

Start with a thorough visual inspection from a distance. Note any obvious body damage, mismatched paint, or uneven panel gaps. These could indicate prior accidents. Examine the tires for wear and tear. Check the tread depth and look for uneven wear patterns, which can indicate suspension problems. Crucially, check the VIN (Vehicle Identification Number) on the dashboard and door jamb. Verify that it matches the VIN on the title and registration. Inspect the vehicle's paperwork, including maintenance records. Regular oil changes and other routine maintenance are good indicators of responsible ownership.

3. Under the Hood: Engine Inspection

Pop the hood and visually inspect the engine bay. Look for signs of leaks (oil, coolant, transmission fluid). Check the fluid levels (oil, coolant, brake fluid, power steering fluid). Examine the belts and hoses for cracks and wear. Start the engine and listen for any unusual noises (knocking, ticking, hissing). Let the engine warm up and monitor the temperature gauge. A rapidly overheating engine is a major red flag. Use your OBD-II scanner to check for DTCs. Even if the check engine light isn't illuminated, there may be pending codes that indicate underlying issues. A P0300 code, for example, indicates a random misfire, which could be caused by a variety of problems.

4. Interior Inspection: Electronics and Comfort

Check the operation of all interior features, including the lights, wipers, radio, air conditioning, and power windows/locks. Test the seat adjustments and ensure that the airbags are intact. Look for signs of water damage, such as stains or mildew. Smell for musty odors, which can indicate a leaky sunroof or a flooded vehicle.

5. Test Drive: Putting it to the Test

The test drive is essential. Pay attention to the following:

Engine Performance: Does the engine accelerate smoothly and powerfully? Are there any hesitations or stumbles?
Transmission Performance: Does the transmission shift smoothly and without hesitation? Are there any slipping or clunking noises?
Steering: Does the steering feel responsive and precise? Is there any excessive play in the steering wheel?
Braking: Do the brakes feel firm and responsive? Does the vehicle stop straight and without pulling to one side?
Suspension: Does the vehicle ride smoothly and comfortably? Are there any excessive bumps or vibrations?

6. Underneath the Vehicle: The Underbody Inspection

This is where the jack and jack stands come in. Safety first! Properly secure the vehicle before getting underneath. Inspect the underbody for rust, damage, and leaks. Check the exhaust system for leaks and damage. Examine the suspension components for worn bushings, leaking shocks, and damaged springs. Look for signs of damage to the frame or unibody. Pay close attention to the CV joints (Constant Velocity joints) on front-wheel-drive vehicles. Torn CV boots can lead to premature joint failure.

Symbols and Key Specs

Understanding symbols and key specifications allows you to interpret technical information about the vehicle. Here are a few examples:

Coolant Temperature Symbol: A thermometer submerged in wavy lines. This indicates the engine coolant temperature.
Oil Pressure Symbol: An oil can. This indicates the engine oil pressure.
ABS (Anti-lock Braking System) Symbol: Usually the letters "ABS" within a circle. Indicates a problem with the ABS system.

Key specs to consider:

Engine Displacement: The volume of air displaced by the engine's pistons (e.g., 2.0L, 3.5L). Larger displacement typically equates to more power.
Horsepower: The power output of the engine.
Torque: The rotational force of the engine.
Fuel Economy: Miles per gallon (MPG).

Real-World Use: Basic Troubleshooting

Let's say you notice a persistent burning smell after driving. This could indicate an oil leak, a coolant leak, or a brake problem. Check the engine bay for oil leaks, look for coolant leaks near the radiator and hoses, and inspect the brake pads and rotors for signs of overheating.

Another example: the check engine light comes on. Use your OBD-II scanner to retrieve the DTCs. Research the codes online to understand the potential causes. Remember, a DTC only points to the *area* of the problem, not necessarily the exact component that's failed. For example, a P0420 code indicates a problem with the catalytic converter, but the underlying cause could be a faulty oxygen sensor or a leaky exhaust manifold.

Safety: Risky Components

Several components pose potential safety risks:

Airbags: Never tamper with airbags. They can deploy unexpectedly and cause serious injury.
Brakes: Faulty brakes can lead to accidents. Always ensure that the brakes are in good working order before driving.
Suspension: Worn suspension components can affect handling and stability.
Electrical System: Short circuits can cause fires. Be careful when working with electrical components.
Fuel System: Leaks can lead to fires or explosions. Be extremely careful when working with fuel lines and fuel tanks. Never smoke or use open flames near fuel.

Always disconnect the negative battery terminal before working on the electrical system to prevent accidental shorts.

Conclusion

Buying a used car can be a rewarding experience, especially when armed with the right knowledge. By following the steps outlined in this article, you can make a more informed decision and avoid costly surprises. Remember, a thorough inspection is your best defense against a bad deal. Happy hunting!

We have a detailed, downloadable diagram outlining all these inspection points and key areas. Contact us to download it and get a head start on your used car search!