The BMW E46 3 Series was made from 1999 to 2006. It is the fourth generation 3 Series, after the E21, E30 and E46. It was replaced by the E90 platform in 2007. The E46 generation is one of the most popular 3 Series models. It combined attractive styling with impressive performance in a relatively compact package. It also is a far more durable platform than the previous E36 3 Series. There are, however, a few areas to pay attention to if you are looking at buying or already own an E46. This does not cover the more specialised M3.
The E46's 2.5-litre M52 (323i, 325i), 2.8-litre M52 (328i) and 3.0-litre M54 (330i) generation engine are quite reliable. On occasion the engine's ECUs (electronic control unit) need to be rebuilt by BMW to fix rough idles, flat spotting or problems with power delivery. This was experienced in 3.0-litre cars with manual gearboxes. Early cars should also be checked for unusual noise from the belt tensioner.
Both the M52 and M54 came with water pumps that really need to be replaced every 60,000 or so miles. Likewise it is recommended that the radiator be replaced at 90,000 miles as preventive maintenance.
Early E46s ball joints are a known weakness but can be replaced with the later and stronger ball joints. Rear coil springs have been known to break. Should this occur, replace both. As on the E36, the E46 3 Series has been known to suffer the dreaded rear floor failure. This occurs when the rear suspension mount literally rips out of the floor. This causes not only a dangerous situation but a hefty repair bill. Some early all wheel drive E46s had issues with the driveline that require replacing the driveshaft, transfer case or rear differential.
Some owners have complained of heavy steering in some model year 2000 cars. BMW has retrofitted some of these cars with later steering racks to add more power boost and make them easier to drive at car park speeds. Also on 2000 model years cars, owners have reported vibrating steering which has been traced to defective front control arms and rotors.
The E46 interiors, as a general rule, hold up well. Problems are usually limited to a failed radio display. The sunroofs are also a problem area on early E46s. BMW's fix sometimes involves replacing almost the whole sunroof. To prevent problems it is recommended to grease the sunroof tracks regularly to keep the sunroof from failing. The sunroof switch has also been known to "lose" the initialisation for the sunroof position. To reset the switch, note the position of the sunroof and then hold the switch in that position for 20 seconds.
All E46 3 Series are great cars if maintained properly. Most of the issues are associated with the early cars but when buying any model, a pre-purchase inspection is recommended.