As you would expect, Series II cars are a better buy; not only because they are younger but the newer series were significantly more reliable than the first one—at least this is what data collected by roadside emergency services like that of the German Automobile Club ADAC shows.
Look for a trailer hitch or the remnants of one. If you find one, don't buy the car. Even if you want to tow something yourself, it's best to find a vehicle that has never towed anything in the past.
Check the tires. Tires that are worn unevenly could be the result of something as minor as underinflation or poor alignment but they could also indicate that some parts in the suspension need to be replaced. Don't forget to check the spare tire as well (it is situated under the trunk, release the bolt inside the trunk with the wheelbrace).
Check the windshield and other window glasses for cracks. A small crack frequently becomes a large one over time. Check the glass of the headlamps and front foglights as well.
Check the chassis and engine numbers to see that they match with the papers. You can calculate the actual production date of the car by looking at the organization number.
Examine the car from a distance of a few meters. Look for uniformity in the color of the paint. Then check it again closely. Cars six years old and newer should not have been repainted. You can check for repaints by looking for non-matching colors or overspray (paint that bleeds over to door handles, bumpers, mirrors and other places where factory paint would not originally appear). Some repaints are very hard to spot—look carefully in various places all over the car. If you find that a trunk or door has been re-painted, that's no reason to automatically panic. Accidents do happen. If you find overspray in different areas of the car, it's safe to assume the car has had a paint job. If you find paint work in the front of a car, it's probably best to find another one: all Citroëns have front-wheel drive and a head-on collision might have badly damaged some parts. Between the black, plastic front grill and the radiator, in front of the engine compartment, there is a cross panel painted in the color of the car body, housing the hood lock as well (see the picture above). The factory glued stickers on it originally (a multilingual warning and stickers specifying the recommended TOTAL fluids). If those stickers are missing, the front might have been repaired and repainted. If in doubt, ask a reliable car mechanic to see whether everything was repaired as it should have been.
Rust should not be a problem on a BX unless it was neglected or some repairs were carried out without paying attention to prevent rust formation. However, check the body, particularly at the bottom of the front wings, the bottom of the doors, on the underside of the body. Some cars have problems with the top hinges of the front door and the area above that. Check the front and rear subframes as well. The exhaust system tends to become rusty over time, it is not too expensive to replace some parts later.
Check that the different body parts are symmetric: bumpers, wings, lamp units should align the same way both on the left and right. If you are at a used car lot having several BXs on display, compare the selected one to the others. The bumpers are not fixed with screws all around, the corner wings are held in place by plastic clips. A little free play is acceptable but really loose bumpers warn of a past accident.
Check that the doors and windows fit closely and are easy to open and close. A door that fits unevenly may indicate rust, neglect or even a collision. Open the driver's door half way and try to lift it to see if the hinges hold the door tightly. The upper hinges of the front doors are known to be a weak spot. Check the rubber sealing all around the door openings.
Look inside the car. Look for excessive wear or tear, but you're not likely to find any (a common piece of advice is to have a look at the clutch and brake pedals but these rubber pads are so cheap and easy to replace...). Look under the floor mats and seat covers, check the upholstery and compare the shape of the seats on both sides, the driver's seat might be much more worn than the other. Make sure the seat is comfortable and that it adjusts to your needs. It should slide forward and backward easily but not loosely. Examine and fasten the seat belts and make sure they are comfortable and snug.
Open the glove box and spend some time looking at the repair history and owner's manual. Take your time. Check the dates of repair against the kilometers you see on the odometer. Check for what was done and what was recommended. Look for regular oil changes and inspections.
Check the battery connections to see that they are clean. Check the oil level to see that it is normal. Oil with a whitish, milky appearance, or with white bubbles, can be a sign of major mechanical problems. Check the coolant fluid; it should not look rusty. Check for leaks and stains under the car, on the underside of the engine, and around hoses and valve covers. Pre-1985 models often have oil leaking from the engine and gearbox. Pre-1986 models often have coolant leakage.
Check whether the ignition key is worn. Start the car. Immediately after the car has been started, check the dashboard. The warning lights of the charging and oil pressure should go out immediately. If the vehicle has ABS, its warning light should go out telling you that the system is functioning. The engine management system warning light works the same way. Sit inside the vehicle for a minute while it warms up. Now it is a good time to try the horn, the signals, the lights, windshield wipers and other electrical items. Play the radio if you'd like to check out the sound system. Try the heater or the air conditioner out but turn it off before going for a test drive to see how the car performs without the latter.
With the engine idling, check the different height settings of the car. It should sink and rise without creaking and without stopping and jumping. Test the suspension spheres. Check the main accumulator (the central sphere behind the radiator) and, if power steering is fitted, the flow distributor valve for leaks. The system normally ticks about once in a minute or even less frequently (measure it with nobody sitting in the car and the engine idling). However, older cars quite commonly have an increased ticking frequency (5 to 10 seconds between ticks). Although this does signal that some parts of the system are worn, the car may perform well for quite a long time, at most with minor repairs over time. However, if the ticking is extremely frequent (1 to 2 seconds between ticks), the main accumulator is underpressurized or even faulty.
After the car has warmed up, check the exhaust pipe. Check for blue smoke that smells burnt. That's bad, and move on to another car if you see or smell any of that; it means that oil is being burned. As a motor warms up, any emissions or water in the exhaust should gradually disappear. Don't buy a car that throws water out the exhaust pipe after it is fully warmed up. It means there is water in the system where it's not supposed to be. Black, gummy soot in the exhaust pipe may mean worn rings, or bad valves, and expensive repairs.
Check the clutch. There shouldn't be any free play, and pressing the pedal shouldn't be too firm. Engage and disengage it several times with the engine idling in neutral and listen for suspicious sounds. If the engine speed drops when the clutch is disengaged, the crankshaft bearings might be at fault and you'd better leave the car alone. Put the car into third gear, apply the handbrake fully, rev the engine up to 3,000-3,500 rpm and release the clutch pedal suddenly. To be on the safe side, be sure that nobody is standing in front of you. If the engine stops immediately, everything is OK. If it goes on, the clutch slips. If the car moves, the handbrake is weak.
When you make a test drive, listen for rattles, squeaks, and wind noise with the windows up, as well as for engine noise: unusual sounds may be signs of major trouble. Observe the oil pressure and coolant temperature meter or warning lamps during the test.
Drive over rough road surfaces and watch for unusual vibrations, noises, or odors. Make several stops and starts, at varying, but safe, rates of speed on a clear, level road surface. The car should accelerate smoothly and should brake without grabbing, vibrating, or pulling to one side. When you step firmly on the brake pedal, it should feel firm, not spongy. If you haven't driven a Citroën before, be careful at first. These cars have wonderful brakes but somewhat different from other cars: it is a so called zero travel type: not the travel of the brake pedal but the pressure on it governs the action of the brakes. For the uninitiated it might seem too harsh at first sight. It is not uncommon for the brake pads to clonk loudly when you apply the brakes while reversing. It is generally only a nusiance, not a real problem. Check the roadholding at 100-120 kmh, wobbling or pulling to one side is bad.
Press and release the throttle pedal a few times and look into the mirror to see if there is smoke from the exhaust pipe.
Try turning at various speeds. Too much sway or stiffness can mean suspension problems. Turn the wheel all the way from one side to the other; power steering should feel smooth, with little or no squealing. Listen for suspicious rattling and squeaking. The steering should feel firm but not stiff.
Check the wheels for "dog-tracking"—have someone stand behind the car as you slowly drive away—if the top of the back wheels head inwards, the rear arm bearing need to be replaced. Unevenly worn rear tires warn of the same problem.
Look for these signs of odometer tampering: white lines between the numbers that do not line up, or vibration of the 1/10-mile numbers while the car is moving.
When you stop the road test, leave the engine idling and check the wheels for excessive heat from the brakes. Look under the hood to check for oil and coolant leaks.