What exactly is the BMW E46? To understand the E46 it is necessary to understand what a BMW chassis code is first. BMW started labeling their models with the “E” designation in 1968 starting with the E3 and E9. The E3 was the sedan version and the E9 was the coupe. The factory uses this terminology to reference the different models. Sometimes these models are different years but essentially are the same car.
BMW will build the same car for several years with only minor changes. This is highly beneficial because it allows them to use the same parts for a span of years. Lets take the E46 for example. The E46 began production in 1998 as a sedan and 1999 as a coupe. Production continued for the sedan until 2005 and 2006 for the coupe and M3. For the most part, all of these cars were the same and share many common parts.
The engines were changed several times during the production run for updates or different powerplant options so the internal motor parts would vary from model to model. 5 different engines were used in the E46. The base option from the dealer is the 2.5L (M52TUB25) and was used in the 323i and 323ci from 1998-2000 but was then updated to 2 different motors with the same displacement, the M54B25 and the M56B25 used in the 325i and 325ci.
The second, larger engine offered was in the 328i and 328ci from 1998-2000 was a 2.8L with the designation of M52TUB28 however, this was replaced in 2001-2005 with the 3.0L M54B30. The M3 had its own separate engine, the 333HP S54B32 and was loosely based of the standard M54. BMW installed these in the M3′s from 2001-2006.
With the exception of the different engines and the unique parts that go along with them, the BMW E46 shares many other common parts. The suspension however is practically identical from 1998-2006 with a few exceptions of course. Those being the sport package suspension and the M3 suspension. All other models, which make up for 70% of the E46 production use the same components in the front and rear suspension. The exact same control arms and bushings and the exact same shocks and struts.
This carries true to the optional equipment parts like the climate control, windows, lighting and other systems. The A\C condenser is the same on a 1998 323i as it is on a 2006 M3. The same goes for the window regulator and washer pump. The body components share these traits also. With the exception of the M3 and coupes, all sedans share the same fenders, hood, trunk and doors. The bumpers are a cosmetic piece that has been updated through the years to give a little variation from year to year.
There has also been little variation in the safety and control systems. Many components of the ABS system and airbag system have remained the same for the span of the E46 although many have received updates over the years. It is very common for a part to be re-designed halfway through production and then re-applied to past models. Many parts become what is called superseded.
Superseding parts is necessary when it has a high failure rate. One prime example is the power steering pumps. They have been updated and changed almost a dozen times due to the fact they have many problems. The early versions were to weak to handle the demands of the steering system and would overheat due to not enough fluid moved through the internal vane.
The most common parts replaced on the E46 are cooling system components. The water pumps and thermostats fail at a very high rate. The black plastic cooling components like the radiator and expansion tank become brittle with age and tend to crack and leak. Other than a few other components, the E46 is rather reliable and perhaps one of the best cars BMW has ever built. It shows in the sales numbers making the E46 the most successful BMW ever.