What Breaks on Used Cars and What to Look For

Buying a used car from a dealership you have never done business with before, or from a private seller, can be a risky proposition. Unfortunately lemon laws do not protect used car buyers in most states, so if you do not properly inspect your vehicle before you purchase it, you may find yourself paying large repair bills weeks later. We asked our mechanics what the most common issues they noticed when inspecting used cars were, and what they would look for if buying a car.




Let’s face it, tires are expensive, and they will eventually need to be replaced. They can also tell you a lot about how the car was driven and maintained. Aggressive drivers tend to put heavy wear on the outside shoulder of the front tires, at the edge of the sidewall. Assume that the car has been driven hard if that area shows heavier wear.

Additionally, check to make sure that all the tires are of the same brand. If there are different brands, ask what was the reason for replacement was, and if they have been regularly balanced and rotated. If all of the tires do not show similar tread wear, or low tread wear, it is likely that this service was not maintained. Tires must have at least 1/16 inch of tread to be legal. Check the tread depth with a tread-depth tool (available at auto-parts stores) or a quarter. Insert the quarter into the tread groove, with Washington’s head down. If you can see the top of his head, the tire should be replaced.



2.) Check the Dipstick!

This seems quite obvious, but a lot of used car buyers neglect to check this crucial step. After test driving the car, leave it running, pop the hood, and use a rag to check the dipstick. The engine oil should be dark brown or black, but not gritty. If the oil is honey-colored, it was just changed. If you are at a dealership and the oil has not been changed, buyer beware! It is likely that they didn’t run a complete inspection.

If the dipstick has water droplets on it or the oil appears gray or foamy, it could indicate a cracked engine block or blown head gasket, two seriously expensive problems.



3.) The Battery

Auto mechanic checking car battery voltage

Batteries are parts that often find themselves needing replacement at very inopportune times. Unfortunately, it is difficult to determine that they need replacement unless you have the correct tools. Fortunately, these tools (known as multimeters) have gotten much more affordable and easy to find over the years. You can order them online, or find them at any major chain that carries automotive supply parts. Some more recent and higher end model batteries will have visual indicators directly on the battery to give you an approximate level of charge remaining.



4.) The Alternator

What a typical Alternator will look like

The Alternator runs hand in hand with your battery, and can be a bit costly to replace if and when it goes bad. Two methods that can show the potential longevity of an alternator are the headlight and battery test. To perform the headlight test, start your car and turn on your headlights. With the vehicle in park, press on the accelerator while a second person observes the headlights. If the headlights flicker, dim or get brighter when the engine revs, your alternator may be going bad. No change in headlight brightness indicates that your alternator is likely fine.

A battery test is just as simple and can be carefully done at home. First, open the hood and start the car. While the engine is running, carefully detach the negative cable from the battery. If the vehicle stalls or dies, the alternator is likely bad. This happens because the alternator is not generating enough electricity to keep the engine running on its own.

Any further tests to measure voltage should be performed by a mechanic, as you will likely have to remove the part to have it tested properly



5.) Any Signs of an Accident

If you are purchasing from a dealer, you should request access to the Carfax, which will give you information regarding the servicing of the vehicle, and any repairs made. Even if the vehicle has no accident history report, inspect the exterior of the used car for any sort of body damage, as not all people report accidents to their insurance company. Any exterior damage could betray interior damage that resulted from such a collision. Take a flashlight and ensure to look underneath the vehicle for scuffs and dents among the undercarriage. Often drivers will go over speed bumps and hills too quickly, and knock items loose, which can be left undiagnosed.

If there is any doubt at this point, make sure to open and close all doors and trunk, checking for wobble. Also listen for any creaks or “jangling chains” in the suspension when entering the vehicle. Feel free to give the car a slight bounce to listen for these noises as well.