Of course, this is not an ultimate guide and I highly recommend reading specialized forums and asking questions about particular brand/year/model there. Reading the real users opinions at sites like carsurveys.org is very helpful, too.
OK, let’s imagine that you have already made your choice and found a car in a local ad or on the Web, or elsewhere and you’ve got an appointment to see the car.
Step 1: Tools Needed
- a flashlight (one big, one small or one small but bright)
- optional: a telescoping mirror
- a newspaper or a piece of plastic (sunscreen works pretty well and is foldable) to put on the ground and look under the car
- a mechanic’s stethoscope (can be found in Harbor Freight for $3-5) http://www.harborfreight.com/mechanics-stethoscope-41966.html
- optional: OBD2 reading tool ($30 on e-bay) or OBD2-USB interface + notebook
- optional: a floor jack.
- liquid soap or cleaning napkin/paper towel.
Where to see the car?
If possible, try to arrange an appointment at seller’s place.
You will see how the cold car starts, check if there are any leaks, and you will also be able to inspect the coolant on cold engine (otherwise it will be a risky business which I won't recommend doing without having an experience).
Step 2: Inspection: Exterior
- open/close all the doors a couple of times checking for unusual sounds which may indicate misalignment associated with the same problem;
- for cars, which have a clear coat over regular paint, check an integrity of this coat on the roof/hood/trunk lid (usual places where the flaking begins). If there are even small “spots”, consider buying another car or plan to sand down the coat and repaint the whole car in a year or so;
- check the wear of tires, especially the front tires. Uneven wear may indicate a problem with alignment, which could be a result of an accident/suspension damage, or tell you about aggressive driving of the owner;
- The tires themselves must have a good tread – an absolute minimum is 2/32” (http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=51) and there should be no blisters or damages.
- brake shoes/brake pads – take your flashlight and inspect the brake shoes (remove the wheel hub covers if needed). Their surfaces should be smooth and the “step” at the edge should not be high (I would say that 1/32”-2/32” is OK). Using a telescoping mirror one can also check the thickness of brake shoes (1/4" will let you drive for quite a while);
- shocks: push one side of the car down and let it go back. If the shocks work properly, the car will go up, then half way down and then oscillations should stop. If there were more oscillations, the shock absorber on this side is on its way;
- body/exhaust/engine from the bottom. Put a newspaper/sunscreen/pad on the ground and take a big flashlight. Check the leaks, rusty spots on the exhaust pipe, and damages of the body. You may look a bit strange in this position :) but replacing an exhaust pipe can easily cost you $400-800 while a one minute inspection costs nothing.
Step 3: Inspection: Interior
- if you are not a smoker, double check for any hints of smoke. If the owner used to smoke in the car, this smell went everywhere and wiping the panels/vacuuming the seats will barely help;
- check all switches, electric windows, sun/moon roof, etc.;
- check the dashboard lights. When the key is turned to the second position, the indicators should illuminate for a couple of seconds and go off when the engine has started. Be aware that in some cases, some sellers disconnect annoying indicators;
- if the “Check engine” or “Service engine soon” light is on, there might be dozens of reasons for that. If you have an OBD2 scanner tool (here I’m speaking about the US market) then you may read and interpret the failure code to estimate the price of repair which may vary from zero (gas tank lid not closed tightly) to a couple of hundred $$ (MAF sensors for some vehicles);
- steering wheel play: open the window, unlock the steering wheel, go out of the car and watch the front left wheel while moving the steering wheel to the left and to the right just till the wheel begins the movement. Check the distance between the leftmost and rightmost positions of the steering wheel – anything more than 30 degrees (5 minutes out of the 60 min hourplate) indicates a wear of rack/pinion/tie rod ends. (Of course, a real play measured in autoshop should be less than 30 degrees but here we estimate it in field conditions by watching the wheel).
Step 4: Inspection: Engine Compartment
- ONLY if the engine IS COLD: open the coolant reservoir and check if there is any oil on the surface. If there is, consider lowering the price or buying something else. If you find rust there, opt for another car – most probably, an engine has been overheated;
- inspect the serpentine belt(s) – there should be no cracks or excessive wear;
- check and squeeze coolant hoses – there should be no visible cracks;
- pull out the dipstick and check oil – it shouldn’t be like a tar and it shouldn’t smell like it’s burnt. The same is applicable for the transmission oil;
- open oil lid and look inside - there should be no sludge or other deposits.
- watch for traces of sealant (black/red) on the joints – this indicates an engine repair and if the owner doesn't explain you what was done, be alert;
OK, it’s time to start the engine
- ask your friend (or the car seller) to crank the engine. Watch the exhaust – it shouldn’t be black or foggy white (some white smoke is OK if there is water condensed in the exhaust system but it doesn’t look like a steam). Blue smoke is not great, either, but it’s better than black or white (in latter two cases just say “thank you and good luck”);
- wait till the coolant warms till the middle of the thermometer scale and the fan starts. If it warms too slow, it’s the thermostat. If the fan doesn’t start, it’s most probably a temperature sensor in the radiator. These repairs are not expensive but you may negotiate a price;
- listen to the sounds – actually, they deserve a whole book. Use a stethoscope to check the bearings (alternator/pump, etc). Be careful not to put the probe too close to a running belt;
- carefully open the oil lid (oil may splash). The engine might hesitate and choke – it’s normal. What we are looking for is an excessive pressure/puffs/blue smoke from under the lid. If this is the case, it indicates worn/stuck piston rings. The repair is (might be) expensive;
- pull out the dipstick once again and check oil color - it shouldn't change compared to what you saw before. It it turned a bit
white and you can see a kind of emulsion, there is a leak of coolant inside an engine.
- ask your friend or the seller to depress gas pedal (if everything is electronic you won’t be able to do it alone). Listen to the sounds. Everything should be smooth, no rattling/knocking;
- check the leaks from below once again – some of them become noticeable only on a running engine;
- ask your friend or the seller to turn A/C on. The clutch should engage, and the A/C should start working – one of the A/C pipes should become really cold in about ~1 minute. If this doesn’t happen, don’t listen to the stories like “it just needs some A/C fluid”. One can of the fluid costs about $15-20 and the seller could have easily added it if it would help. Most probably, there is a serious leak and the pressure switch disengages the clutch. The repair is usually expensive.
Step 5: Driving Test
- on a straight road – leave the car running without touching the steering wheel. Check if it pulls to the side. Test the brakes and simulate emergency braking. No uneven braking is expected. Check the behavior of the transmission – there should be no slipping or hesitation at any speed;
- on a rough road near the wall: open the windows and listen to the sounds. No rattling/squealing/etc is expected;
- on a slope: cars with automatic transmission are not supposed to roll back in “D” position or to roll forward in “R”;
- Make a final short inspection under the hood when you are back.
Step 6: Making Up Your Mind
In some cases, the sellers don’t know about certain problems of their vehicles or think that the problem is easy to fix.
If you explain it properly, the negotiation will go easier. Of course, in some cases, the car is worth buying even if there are minor problems and the seller is stubborn - compare it to other vehicles you've seen.