BMW Water Pump and Timing Belt/Chain – 2001 325i E46 M54/56
This answer is applicable for many BMWs in addition to the one listed below.
I have a 2001 325i with 91,000 miles. No one will give me a straight answer on when the timing belt should be changed. When should it be changed and what would be the estimated cost? Also should the water pump be changed at the same time since the front of the motor is already apart?
The M54/M56 engine in your 2001 325i (and many other BMW models; X5, X3, E39 5-series, E60/61 5-series, Z3, Z4) does not use a timing belt. The cams are driven via a timing chain that does not require any regular maintenance or replacement until 150,000 or more miles. At this point, an inspection of the chain and the tensioner and guide rails would be recommended. Most likely, all will be fine (with this M54 engine).
Some BMW engines, such as the M60 and M62 V8s and the M42 and M44 4-cylinders, are starting to show broken chain guide rails in the 150,000 to 200,000 mile range. This will cause a rattling or slapping noise from the timing chain area.
The water pump on these engines, however, should be replaced at around 60,000 miles, due to historic failure data. It’s a lot easier, and usually less expensive, to replace the pump before it fails (out on the road someplace). We typically also replace the accessory drive belt and the tensioner and idler pulleys (for the belt). The Bentley repair manual details all of this. Additionally, I’ve attached a copy of the Spring 2007 issue of our Fast Times newsletter, which contains an article on replacing the water pump on a 2001 330i (similar to your 325i).