18/12/2023
Testing a second hand used car before you buy it.
First you need to get the VIN which is a worldwide number that every Vendor has for each car and get it checked by CarVertical, one of the best sites to check the history of a car by VIN, including accidents and real kilometers.
Whit engine cooled, switch engine on and check the water expansion deposit for bubbles or yellow deposits on the liquid. They mean a blown engine head gasket or rust inside the engine due to use of water instead of coolant.
Second you should drive at low speed (70–90 km/h) and check if by gently applying brakes you see or feel the wheel vibrating - this will show when brakes are warped. You also check the gearbox by gear up and down through all gears. Try also a bumpy road where you check for unexpected suspension noises, while turning a bit the wheel right-left-right, like “clecks or “clonks”.
Drive the car on a flat straight road without slopes and release the driving wheel at low speed while checking if the car deviates to one side. Also check each tire for asymmetrical worn. Could just mean bad alignment but could mean chassis is not good anymore because it hit something. During slow speed free the driving wheel and suddenly slightly hit the brakes and see if driving wheel reacts by turning slightly and suddenly to any side.
Third, you have to drive it on a highway and push the accelerator on each gear and try to go to the speed limit of the car, there are thing you can notice only at speed like vibrations, if all things below the car are correctly attached, if exhaust sensors are good allow the engine to go full charge. During acceleration regarding turbo cars you should check for loud whistles that may show turbo is worn out.
You should also see if all gears go up ok at speed. Also test briefly brakes and see if the car tends to change direction due to faulty brake pumps or pistons. Also, check if all gears go up well at speed. Also try a road with some some sand or wet and try the ABS by suddenly pushing the brake pedal hard and see if you feel a vibration on your foot and hear the corresponding “rrrrr” noise while the car stops.
Then you stop the car while hot and try to check if cooling fan on radiator switches on by continuously accelerating at 2800–2000 rpm until fan engages and you see it (you may ask the salesman to do it, while you check the fan). During this test also check the temperature to see if it remains stable or does not go beyond the normal limit of 80–100 degrees Celsius limit, otherwise you have a faulty thermostat or fan problems or air in the water pump circuit. Check for water leaks on the bottom plastic fairing below the engine. Also
Inspect the exhaust tip with your finger and see if it is oily. Also ask the sales man to accelerate and deaccelerate shortly to see if smoke comes out - blue smoke smells to burned oil. These two procedures will show if engine is consuming too much oil. White smoke while engine is hot may mean turbo oil leaks.
Carefully inspect all the airbag panels if they aren’t broke or seem to have been fired after an accident.
Check the shock absorbers by using your weight over each wheel to wobble the chassis making it oscillate to its resonance frequency and then suddenly release it while check if it stops immediately or if it continues to wobble by itself.
Also check from each side of the car if all panels adjust correctly and symmetrically. In the front and back with panels hoods open you may want to check for “too new” parts that may have been replaced or if headlights reflectors and protections have both the same usage level. If something is not right here means the car hit something or was hit by something.
Also check your gearbox clutch disk: with the car stopped, pull the handbrake, engage first gear and check if car still tries to raise its front wheels and pull, while you try to gently release the clutch pedal. It should not smell like if it was burning something for a short test.
Then you check the electrics of the car by switching on all light and heating/AC system and still check if temperature does not go up.
Finally you pay a close look at the wheels cavities to check for spilled oil from suspension shock absorbers or brakes. Also check the bottom of the car from above and below to check for spilled oil on parts of the engine compartment parts. Check for smelling to oil or gas that may indicate leaks somewhere over hot surfaces.
If possible take it to a washing a manual washing machine and direct the water jet to every door, windshield and luggage compartment lid and also to the opening roof if it exists and check for infiltrations.
For cabrios with soft or hard hoods try opening and closing them and see if they go quickly up and down. If not it means hydraulic cylinders or main pump are worn out or
If the car passes all these tests it should be Okay :-)
