BMW 740i
Closed-deck aluminium block as standard — a feature normally reserved for racing engines. Water-cooled turbo with mechanical wastegate linkage that rattles at cold start — by design, not dangerous. Barely audible at idle; from 3,000 rpm a rich, deep six-cylinder thrust builds linearly to 6,500. The B58 sounds fuller than the S55 from outside — but inside the motorsport aggression is absent. Dual injection (direct + port) reduces intake valve carbon build-up significantly. The PCV membrane in the valve cover is the known weakness: BMW had to extend the warranty to 15 years. Plastic oil filter housing cracks around 100,000 km — coolant mixes into oil, act immediately. Oil changes every 10,000 km; inspect the cooling system from 70,000 km. Tuning: Stage 2 brings 500 hp — the closed deck makes it possible.
Inline-six 7 Series
B58 in the 7 Series — authoritative, the 740i never puts a foot wrong.
Engine Weaknesses 12
On B58-equipped M140i/M240i the oil filter can disintegrate on first change and distribute filter material through the oil circuit. BMW covers the costs with proven service history.
Symptoms: Oil pressure warning, metallic noises, engine damage after oil change
The plastic oil filter housing becomes brittle from heat cycling and cracks — often during oil changes from overtightening the filter cap. Coolant and oil mix; engine damage likely if unnoticed.
Symptoms: Milky oil on the filler cap, coolant loss without visible leak, oil pressure warning, coolant level drops slowly
The PCV membrane in the integrated valve cover tears or hardens from heat cycles. Crankcase builds positive pressure, oil is forced through seals. BMW extended the warranty to 15 years/150,000 miles.
Symptoms: Whistling or squealing from the engine bay, white or blue smoke, rough idle, oil in the charge pipe or air filter
Many B58 owners observe a regularly dropping coolant level without external leaks. Suspected components are heat exchanger gaskets, plastic lines, and the expansion tank cap.
Symptoms: Coolant warning message; coolant level regularly low after topping up; no visible leak on the ground
The mechanical seal of the belt-driven water pump fails prematurely. Coolant seeps from the weep hole below the pulley. Often only slowly detectable — early visual inspection is advisable.
Symptoms: Coolant residue or drops under the engine, coolant level drops without major visible leak, coolant level warning
The small plastic bleed hose between the oil filter housing and expansion tank becomes brittle and develops hairline cracks. Often perceived as coolant loss with no obvious cause.
Symptoms: Coolant loss without visible puddle, damp spot at oil filter housing, pressure loss in cooling system
The standard plastic charge pipe between the intercooler and throttle body bursts under boost pressure — especially on tuned cars or in summer. Immediate limp mode.
Symptoms: Immediate power loss, limp mode, audible hissing or bang when it splits, engine runs with severely reduced power
Like the B48, the B58 turbocharger wastegate linkage rattles by design on cold start and at low revs. BMW has issued a specific repair kit as a goodwill measure.
Symptoms: Metallic clattering or rattling from the turbo area on cold start; sounds like a loose metal bolt; usually only in the first few minutes
VANOS solenoid valves on the B58 get clogged by oil-contaminated deposits or fail electrically. Individual valves are cheap to replace; delay risks follow-on damage to the camshaft phasers.
Symptoms: Idle fluctuation; power loss below 3,000 rpm; ticking on cold start similar to a diesel; fault code 2A82 or 2A87
Direct injection does not wet the intake valves — blowby vapours bake carbon onto them. The B58 also has port injection which slows carbon build-up significantly compared to pure DI engines.
Symptoms: Rough cold start, power loss at higher revs, misfires, increased fuel consumption
The auxiliary belt tensioner rattles on cold start — sometimes from just a few thousand kilometres. BMW warranty repair, but problem can return after replacement.
Symptoms: Metallic rattling or clattering on cold start, noise fades after warm-up, worsens when AC is switched on
The rubber valve cover gasket hardens from extreme heat cycling and leaks oil onto spark plugs and the engine block. Separate from the PCV issue — pure seal degradation without membrane failure.
Symptoms: Burning oil smell, oil marks on engine block below valve cover, oil on spark plugs, slight oil consumption
Vehicle Weaknesses 16
Wiring harness problems or CAN bus faults cause fault messages across many control units simultaneously.
The PHEV system has no alternator. A fault in the SME module opens the contactors and the 12V battery discharges while driving.
Air bellows become porous from around 100,000–150,000 km; the compressor overheats from frequent pumping and fails. Car sags on one side or completely.
Signal fault in the motor position sensor can deactivate hydraulic brake assist. Approximately 1 million vehicles worldwide.
Recall KBA 16187R: a potentially misrouted cockpit wiring harness can be damaged during cabin filter replacement. A short circuit can cause smoke or fire — 337,374 vehicles worldwide affected.
G11 sags unevenly at all four wheels overnight. No fault code stored.
NOx sensor upstream of the SCR catalyst fails. Complete tank replacement costs 2,500–3,000 €.
Blocked or porous panoramic roof drain tubes channel water into the cabin instead of outside. Water collects in the headlining and runs toward the battery or control units.
Driver assistance systems on the G11 (lane keep assist, blind spot warning, junction assistant) malfunction frequently and require software updates or camera reinitialisations.
Faulty comfort access system draws continuously elevated current and drains the battery.
The interior door opening button integrated into the diamond light strip fails and no longer illuminates. Climate controls on the same side can also fail simultaneously. BMW replaces the entire light strip — approximately 4 weeks lead time.
Heavy luxury saloon with large brake discs. Surface rust after standing causes squealing.
Over-the-air updates can cause malfunctions: eSIM loses connection, settings reset.
The i7 shows significant range loss in cold conditions due to battery thermal management.
The G70's integrated eSIM module frequently loses connection at vehicle startup. BMW addressed the issue with software update 11/2023.42; improvements confirmed by several owners.
Soft-close doors don't retract reliably; comfort exit function stops working after OTA updates. Various body electronics functions show sporadic failures.
Reports & Tests
13 owner complaints filed with NHTSA (2015–2022). Most reported: Engine (3), Electrical (3), Seat Belts (2).