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E90 Common Problems by Engine
How reliable each E90 really is — N52, N54, N55, N20, the diesels and the S65 M3, the issues they all share, and which engine to buy.
Read the guide →335i Common Problems
The turbo deep-dive — the twin-turbo N54 versus the single-turbo N55, problem by problem, and which to buy.
Read guide →N54 Problems — Which Matter
The legendary twin-turbo six, ranked honestly — the failures that count, and the ones that are mostly myth.
Read guide →M3 Problems (Manual & DCT)
The S65 V8 M3 — rod bearings, throttle actuators and the manual-versus-DCT choice.
Read guide →Buying
DIY Guides
Electric Water Pump & Thermostat
The defining E9x job — replacing the failure-prone electric pump and thermostat, including the all-important electronic bleed.
Read guide →Oil Change (N52 & N54)
The routine service done right, with the correct oil for your engine.
Read guide →Front Brake Pad & Rotor Replacement
Pads, rotors and the wear sensor up front — the straightforward half of the E92 brake job. In the works: the rear (with the electronic parking brake).
Read guide →Spark Plug Replacement
Fresh plugs by engine — the right gap and interval for the N52, N54 and N55, plus the colder, tighter-gapped plug a tuned turbo wants. (Walnut blasting guide coming.)
Read guide →Valve Cover & Filter Housing Gaskets
The E9x's two classic leaks — how to tell which is which, and reseal both yourself.
Read guide →Cabin & Engine Air Filters
The easiest wins on the car — both filters swapped in under half an hour with basic tools.
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