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 severity
Typical 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 severity
Typical 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 severity
Typical 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 severity
Typical 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.
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 severity
Typical 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
Owner tips
Run premium fuel exclusively and do short oil change intervals (5,000-6,000 mi) to minimize carbon buildup and turbo wear
Have transmission fluid changed at 60,000 mi regardless of BMW's 'lifetime' claim—prevents cooler and valve body issues
Budget $2,000-3,000 annually for repairs once past 60,000 miles; these are complex, expensive cars to maintain
Find a BMW specialist with ISTA diagnostic software—generic scanners miss half the faults on G11 chassis
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.
Fitment notes: AGM battery required; located in trunk; requires battery registration after replacement
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Every control module on the 2018-2021 BMW 740i — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
⚠️ Basic VIN coding; most aftermarket tools can perform
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2018 BMW 740i 3.0L I6 Turbo B58 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Mechanic · 20+ years.