There has been several used cars that I have bought where I have later found problems that I should have found before I handed over the money.
Sometimes these have been minor problems but some have been major. Like the Toyota I bought with a cracked cylinder head.
Here are a few simple but important points that are most relevant for cars over 5 years old/100,000km.Under Bonnet/Car Checks
If the engine bay shows signs of just being cleaned then you should probably look again after a test drive. That's probably a good idea regardless.
Look for any oil leaks and find the source of them. Bring along a rag so you can clean the suspected area then take the car for a test drive then check again to confirm your suspicions. Most cars leak some oil and most leaks are not always something to worry about but ocassionally it can be a sign of a major problem.
Take, for example that Toyota I mentioned earlier. I saw some oil leaking down the side of the head but without taking the time to check properly I guessed it was coming from the cylinder head cover, which is pretty common. Had I inspected closer I would have seen the true cause and walked away immediately.
Quality coolant is important for most of the cars on the road these days. Look for coloured coolant (green, red or blue usually) and be wary of clear and very wary of rusty coolant. Any oily film in the coolant expansion tank or radiator requires further investigation.Test Drive
Ideally you want to start the car from cold. Unfortunately, this is not always possible but yould could easily find yourself with a car that is difficult to start when cold. That could be something minor or could indicate more significant problems.
If looking at a car with higher mileage then looking for any exhaust smoke is very important. Blue smoke means the car is burning oil. White smoke means water which could indicate a blown head gasket but even a healthy engine will have steam coming out of the exhaust when warming up. A certain amount of black smoke is normal when accelerating very hard.
You should check behind the car when it is first started. You should also check for smoke during the test drive during a brief burst of hard acceleration to near maximum revs. You should also find yourself a steep hill and drive down it at reasonable revs (over 3,000 rpm) with the throttle closed. At the bottom of the hill start accelerating and keep your eye on the rear view mirror.
You may not see small amounts of exhaust smoke from the driver's seat but you will definately see some if there is a major problem. Ideally you could have someone watching by following in another vehicle or standing at the side of the road.
If you do see any blue smoke you need to make note of when it occurs and seek further advice. Depending on the symptoms, it could indicate anything from worn valve guides to worn cylinder bores (or cracked cylinder heads).
Don't be put off doing a proper test drive by not wanting to scare the elderly/pregnant owner (that's what happened with that damn Toyota). Warn them that you need to do a proper test drive and if they want to come along then fine, if they refuse then be very wary of the car.
Run all four wheels over bumps to check for any clunks that would indicate that steering or suspension parts are worn and need replacing.
Take the car for a long enough drive for it to get to normal operating temperature. Most modern cars will get to half way on the temperature gauge and stay there. Any significant deviation downwards might indicate a simple faulty thermostat, any deviation upwards could mean the cooling system is not working properly and the car may overheat or have been overheated which could be real bad.
Run the heater and air conditioning to ensure they are both working.
When you get back from the test drive make sure that the car starts when hot too.Body checks
Many older cars will have had some damage repaired at some point in their life and as long as the damage has been fixed well it's not usually a problem.
But body damage and paintwork issues can be difficult and expensive to rectify.
If the clear coat is peeling anywhere on the car, it can be a sign of either poor repainting, or it could be the original paint which means it is probably going to happen elsewhere on the car soon.
Signs of poor paint repairs are evidence of masking around window seals and mouldings, and masking on the inside of things like bonnet vent holes. If you see any obvious things like this then you should question how well the car was fixed.Other Checks
I thoroughly recommend that you research the model that you are looking at first.
For virtually every model there is excellent advice to be found from other owners and enthusiasts on the Internet.
Find yourself a forum or message board that deals with that model, read previous posts and learn the common problems. Search for any posts on common problems and if you can't find anything ask for advice on what to look for.Links:
Good advice: http://www.samarins.com/check/engine.html