The 2018 740i with the B58 engine is generally reliable for a BMW flagship, but the ZF 8-speed transmission and its supporting systems are the Achilles' heel, along with some carbon buildup issues typical of direct-injection turbos.
Transmission Oil Cooler Failure
Common · high severityTypical onset: 60,000-90,000 mi
Symptoms: transmission overheating warnings on iDrive, limp mode activation, harsh shifting or delayed engagement, transmission fluid leaking near front of engine bay
Fix: Replace transmission oil cooler and lines, flush transmission fluid. This requires dropping the subframe for access on the 7-series. 6-8 hours labor plus parts.
Estimated cost: $1,800-3,200
Transmission Mount Failure
Common · medium severityTypical onset: 50,000-80,000 mi
Symptoms: clunking when shifting from Park to Drive, vibration at idle in gear, excessive driveline movement felt during acceleration, visible tears or fluid seepage from mount
Fix: Replace transmission mount assembly. Requires supporting powertrain and dropping crossmember. 3-4 hours labor. Often discovered during oil cooler work.
Estimated cost: $800-1,400
Carbon Buildup on Intake Valves (B58 Direct Injection)
Occasional · medium severityTypical onset: 80,000-120,000 mi
Symptoms: rough idle or misfires, reduced power and fuel economy, hesitation on acceleration, P0300-P0306 misfire codes
Fix: Walnut blasting intake valves requires removing intake manifold. 4-6 hours labor depending on access. The G11/G12 7-series has tighter engine bay packaging than the 5-series.
Estimated cost: $800-1,500
High-Pressure Fuel Pump Failure
Occasional · high severityTypical onset: 70,000-110,000 mi
Symptoms: long crank or no-start condition, rough running and power loss, fuel pressure fault codes, metal contamination in fuel system if pump grenades
Fix: Replace HPFP and filter, flush fuel rails if contaminated. On the B58, pump is on the engine side accessible from top. 2-3 hours labor if clean failure, 8+ hours if metal debris requires injector replacement.
Estimated cost: $1,200-2,000 (clean) / $4,000-6,500 (contaminated)
Coolant Crossover Pipe / Thermostat Housing Leaks
Occasional · medium severityTypical onset: 60,000-100,000 mi
Symptoms: coolant smell in cabin or engine bay, visible coolant seepage at front of engine, slow coolant loss between services, low coolant warning
Fix: Replace thermostat housing assembly and crossover pipe with upgraded components. Tight access requires removing intake components. 3-5 hours labor.
Estimated cost: $1,000-1,800
Air Suspension Compressor and Strut Failures
Occasional · medium severityTypical onset: 70,000-120,000 mi
Symptoms: vehicle sagging at one or more corners overnight, suspension fault warnings, compressor running excessively, harsh ride quality
Fix: Replace failed air strut(s) or compressor. Front struts 2-3 hours each, rears 2 hours each, compressor 2 hours. All 740i models have air suspension standard—no escape from this one.
Estimated cost: $1,500-2,200 per strut / $2,000-3,000 compressor
Buy only with comprehensive records and a pre-purchase inspection by a BMW specialist—great to drive but expensive to fix when the nickel-and-diming starts around 60k miles.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.