BMW 320i E90

The N46 engine uses a timing chain with a hydraulic tensioner that can lose oil pressure overnight as the release valve weakens. This causes a distinctive rattle during the first few seconds after a cold start. The issue typically develops between 80,000 and 130,000 km. If the rattle lasts more than a few seconds, the chain, guides, tensioner, and sprockets all need replacing. BMW released an updated tensioner part number. At an independent BMW specialist, expect €1,000-1,500 for the full replacement. BMW dealers quote €1,500-2,200. Ignoring the rattle risks the chain skipping teeth, which causes valve-piston contact and catastrophic engine damage.

The N46 uses BMW's Valvetronic system with an eccentric shaft sensor mounted behind the oil filler cap. Over time, oil migrates through the sensor seal and fills the electrical connector, causing sensor faults. Symptoms include check engine light, rough idle, and reduced power. The sensor itself costs around €80-120, but the repair often requires replacing the valve cover gasket at the same time and is labour-intensive (3-4 hours). Total cost at an independent shop runs €400-800, or €800-1,500 at a dealer. If the eccentric shaft itself has been damaged from prolonged driving with a faulty sensor, the repair escalates significantly.

The Valvetronic motor adjusts intake valve lift continuously. When it fails, the engine enters a default mode with limited power output and a check engine light. The motor costs approximately €250-400 for the part. Labor is 2-3 hours at an independent shop, bringing the total to €600-1,000. At a BMW dealer, expect €1,200-2,000. The motor tends to fail more often on cars that have been driven with a leaking eccentric shaft sensor for an extended period, as the electrical issues compound.

The N46 is known for developing oil leaks from multiple locations as gaskets age. The three most common sources are the valve cover gasket (€300-500 at an independent shop), the oil filter housing gasket (€250-400), and the vacuum pump seal (€200-400). The vacuum pump in particular is a well-documented N46 weak point, with the internal diaphragm degrading and allowing oil to seep past. Many E90 320i owners end up addressing all three leak points within a few years of each other, typically after 100,000 km. If all are done simultaneously, expect €800-1,500 in total. Left unaddressed, oil can drip onto hot exhaust components or contaminate the cooling system.

The E90 uses an electric power steering rack where the assist motor can fail without warning. When this happens, steering becomes extremely heavy at low speeds. BMW does not sell the motor separately, requiring a complete steering rack replacement at the dealer for approximately €2,000-2,500 including labour. Specialist repair shops can rebuild the motor unit for €800-1,200. The replacement units from BMW carry only a one-year warranty and reportedly suffer from the same design weakness. This issue can occur at various mileage points but is most commonly reported between 100,000 and 180,000 km.

Failed window regulators are a widespread E90 issue. The plastic clips that hold the cable mechanism break, causing the window to drop into the door or move very slowly. Rear windows are affected more often than fronts. A replacement regulator costs €80-150 for the part, with about 1-2 hours of labour. Total repair at an independent shop runs €200-350, or €350-500 at a dealer. Repair clips are available as a cheaper temporary fix (€15-30) but the full regulator replacement is the lasting solution.

The E90 uses a rubberized soft-touch coating on interior door pull handles and various trim pieces that degrades over time from heat, UV exposure, and skin oils. The coating becomes sticky, then starts peeling. This is a cosmetic issue that affects virtually all E90s over 10 years old. BMW dealer replacement of all four door handles costs €500+. Aftermarket replacement handles are available for €30-60 each. Refinishing services or vinyl wrapping offer cheaper alternatives at €100-200 for the entire set.