BMW 3 Series E90/E91/E92 Common Faults: N47 Chain, Electric Water Pump and VANOS
E90 3 Series cars are still daily drivers around London. This is the workshop list: diesel chain rattle, electric water pump, VANOS, battery drain and the rust BMW never fully solved on this generation.
Which E90 you actually have
E90 saloon, E91 estate, E92 coupe and E93 convertible (2005–2013) share a lot of hardware. Petrol N46/N52/N53/N54 and diesel M47/N47 all show up at Forest Road. The diesel 320d N47 is the car people ask about first because of the timing chain. Petrol cars more often come in for VANOS, electric water pumps and coil packs. We identify the engine from the VIN in ISTA, not from the badge.
N47 timing chain — the expensive rattle
On N47 the chain sits at the back of the engine. A cold-start rattle that lasts more than a second is not “diesel nailing”. If the chain has jumped, valves meet pistons. We inspect with ISTA correlation data and a mechanic’s listen; replacement is an engine-out or a specialist in-situ job depending on the variant. Budget properly — this is not a £200 tensioner clip. See our dedicated N47 chain guide for the decision tree.
Electric water pump and thermostat
The electric pump on N52/N54 petrols fails by going slow, then throwing an overheat warning. Coolant on the floor under an E90 in a Redbridge car park is often the pump housing, not a “head gasket”. We replace pump and thermostat as a pair when the pump is original, bleed with ISTA, and check the auxiliary radiator on the M Sport packs.
VANOS, DISA and ignition
VANOS solenoid screens clog on neglected oil. DISA flaps on N52 rattle and can drop into the intake. Ignition coils are a routine MOT-week failure when a misfire light appears. None of these need a dealer to diagnose; they do need ISTA to confirm which bank and to clear adaptations after the repair.
Body, rust and electrics
Rear-arch and jacking-point rust is an MOT regular. Battery drain from the boot-lid module or a tired IBS is a classic “it was fine until I left it three days”. We test sleep current before throwing a battery at it. iDrive CIC units that reboot on speed bumps are a known hardware fault; sometimes a solder rework, sometimes a used unit plus coding.
Is an E90 still worth repairing?
A clean 320d with a documented chain or a 330i with a fresh pump is still a sensible London car. An auction 320d with a rattle and no history is a parts donor. We will say which is which after an ISTA inspection at Hainault.