Aug 17, 2011

Used Car Buyer's Guide: Part II

Part II: Inspecting the Engine, Tires, and Brakes

In an ideal situation, you will try and contact the seller and arrange to view the car before it has been driven that day.  You want the engine to be cold so you can see how it starts up for the first time of the day.  Many issues with a poor running engine are not present when the engine has reached normal operating temperature. 

Before starting the engine, open the hood.  Take a close look at the general appearance of the engine.  Is it clean?  Is it covered in leaking fluid?  Are there any obvious smells?  It is okay if the engine does not appear to be brand new, but it should be relatively clean and orderly.  Next take a look at the belts and hoses.  Do they look old and cracked?  Feel the hoses, they should be pliable.  They should not be brittle or show any signs of cracking.  If you can, grab the engine accessory belt.  Twist it with your fingers so that you can see the side of it.  Make sure there are no cracks or abnormal wear.

Take a look around the engine compartment and look for any wires that look out of place.  Modern cars have wiring that is contained inside a wiring harness.  Random wires that are of non-matching coloring can indicate lazy repair work or aftermarket accessories such as stereos and alarms.  It is important that any non-factory wiring is done properly. 

Next, check the oil.  You may want to take a paper towel or rag with you for the inspection.  Always, make sure the car is on a level surface.  Pull out the dipstick and wipe it clean.  Return the dipstick into the tube and wait a few seconds.  Pull it back and take a look.  It should be in the operating range on the dipstick.  That usually means it will be between two marks on the end of the stick.  Also, take a look at the oil.  You can even smell it.  If it smells burnt or smells of gasoline, those are indicators of possible problems.  The oil should range in color from the color of honey to dark brown.  If it is really black, it is probably pretty old and needs to be changed. 

Also, if the oil looks like a chocolate milkshake, it is time to walk away.  Oil that looks like chocolate milk has water in it and that usually indicates a blown head gasket.  Ask the seller when it was last changed.  Also, ask to see receipts for oil changes so that you can establish a service history. 

Water in oil indicating a blown head gasket
I always check the water reservoir.  Make sure it is at the proper level indicated on the reservoir.  Also, it should be a color other than clear indicating the presence of anti-freeze.  Different manufacturers use different color fluids.  Usually, you will see green, blue, orange, or even pink/red.  Also, make sure there are no traces of oil in the water.  Like water in the oiling system, oil in the water system can indicate serious engine problems.

When checking out a vehicle, it is always nice to have a friend with you.  They will come in handy when it comes time to start up the car for the first time.  Have them start the car while you walk to the rear of the vehicle.  Watch the tailpipe as they start the car.  You are checking to see if there is any smoke exiting the tailpipe upon start-up.  If you are looking at a modern vehicle, there should be no smoke.  Black or blue smoke at the initial start-up is an indicator of several different engine issues ranging from minor to quite serious. 

Smoke upon cold start

Listen carefully to the engine as it starts.  There should be no abnormal sounds.  The engine should start after a few revolutions.  It should come to life and settle in to a steady and smooth RPM.  There should be no sputtering or rough running.  If these symptoms are present, there could be problems with the car's cold starting system.  Let the engine run for a few minutes and make sure that no problems exist as it warms up.  About five minutes should do.  If there are any abnormal sounds emanating from the engine, it would best to have the car evaluated by a professional if you are still interested. 
Now, we will take a look at the tires.  Take a cursory look at the tires.  Make sure they are all the same size.  They should be the same brand.  At the very least, the rear two tires should match and the front two tires should match.  Mismatching tires from side to side can create numerous problems and should be avoided.  Take note of the brand of tire.  It is always a good idea to do a google search of the tire brand and model and read some reviews.  Cheap tires can create havoc on your car.  Now, start in the front, turn the steering wheel to one side and then inspect the exposed tire.  The tread depth should be equal from the inside to the outside of the tire.  If one edge is clearly worn more than the other, the car has alignment and possibly suspension issues.

Uneven wear from left to right (camber wear)
Get an idea of the overall tread depth.  Now, repeat on the other side and the rear tires as well.  Some states have a law that says your tread depth must meet a minimum requirement.  The following diagram demonstrates the idea. 

Minimum Tread Depth

Next, you want to have a look at the brakes.  Start by inspecting the rotors.  The brake rotor is a steel disc that sits behind the wheel.  The brakes work by creating a clampin action around the brake rotor.  The clamping is done by the caliper and it squeezes the brake pads against the flat surfaces of the rotor.  A healthy rotor should have a failry uniform surface.  There should be no heavy gouging, grooves, or pitting.  Some fine lines are acceptable.  Rotors have a finite life and are replaced once they have reached their wear limit. 

Viewing the rotor through the wheel

Deep Grooves in Center of Rotor

Thick edge on rotor indicates heavy wear
This is how a new rotor looks
Checking brake pad life is important, but is often difficult without taking the wheel off.  You might be able to get a look at the pads through the wheel.  They will be held inside the brake caliper and are in direct contact with the rotor.  If you can see the pad, it should be no less than 1/8th of an inch.  That is about the same as two pennies stacked. 

New brake pads viewed with wheel off
If you are not able to view the brake pads, ask the seller for documentation of the last brake job or have a professional inspect the brakes.  If that is not available, you will need to consider that you may be replacing the brakes after purchasing the car. 

You can find the next installment of the buyer's guide linked below. 


  1. I hope you have a nice day! Very good article, well written and very thought out. I am looking forward to reading more of your posts in the future.

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