BMW 740d E65

The E65 740d uses the ZF 6HP26 six-speed automatic, which was the first car to use this gearbox. A small seal between the mechatronic unit and the transmission case degrades over time, causing the transmission to lose hydraulic pressure. Symptoms include harsh shifts, delayed engagement, getting stuck in one gear, or limp mode. BMW originally considered this a sealed-for-life unit, but fluid and filter changes every 60,000-80,000 km are essential for longevity. If neglected, solenoid failures and clutch pack wear follow. Mechatronic rebuild costs €1,500-2,500 at a specialist, while full transmission replacement can reach €3,500-4,000. Cars with confirmed regular fluid changes are significantly less likely to have these issues.

The E65 was BMW's first car with the MOST (Media Oriented Systems Transport) fibre-optic bus connecting the iDrive, navigation, amplifier, telephone module, and other multimedia units. The MOST bus uses a ring topology, meaning one failed module can bring down the entire multimedia system. The most commonly failing modules are the CCC navigation unit, the audio amplifier, and the Bluetooth/telephone module. The CCC unit typically fails after 5-8 years due to a processor chip separating from the PCB or capacitor failure. Dealer replacement costs €800-1,500, while specialist repair services charge €200-400. A complete MOST bus diagnosis and repair session can cost €500-1,000 if multiple modules are involved. Battery drain is a common secondary symptom when a MOST module fails to enter sleep mode.

Many E65 740d models were optioned with rear self-levelling air suspension. The rubber air bags deteriorate over time, developing cracks and leaks. When an air strut leaks, the compressor runs continuously to compensate, which eventually burns out the compressor as well. OEM replacement air struts cost €400-600 per side, while the compressor costs €500-800. Labor is 2-3 hours per strut. Total repair for both struts plus compressor can reach €2,500-3,500. An aftermarket coil spring conversion kit is available for approximately €400-600 for both rears, which eliminates the air suspension entirely but changes the ride character.

The M67 V8 diesel, like all diesels of this era, accumulates carbon deposits in the EGR system. Short-trip driving accelerates this buildup significantly. Symptoms include rough idle, power loss, black smoke, and eventually limp mode. An EGR valve replacement costs €300-500 for parts plus 2-3 hours labor. On the M67, access to the EGR system is more difficult than on an inline-6, increasing labor costs. Some owners opt for EGR delete kits (€100-200), though this affects emissions compliance. Cleaning the EGR valve can extend its life but is typically a temporary fix if the carbon buildup is severe.

The M67 uses twin electronically controlled turbochargers with variable geometry actuators. These actuators can stick from carbon buildup (particularly with gentle driving and short trips) or fail electronically. Symptoms include intermittent limp mode, fault codes 3F67/4D81, and sluggish acceleration. If caught early, actuator repair costs €800-1,200. If the actuator failure damages the turbo internals, a single turbo replacement runs €1,500-2,000, and since the M67 has twin turbos, worst-case scenarios can reach €3,000. The M67's twin-turbo configuration makes access and labor considerably more expensive than on inline-6 diesel BMWs.

The E65 features BMW's Dynamic Drive system, which uses hydraulic actuators on the anti-roll bars to reduce body roll. The system operates at high pressure and uses thin hydraulic fluid that tends to find every possible escape path over time. Common leak points include the actuator seals, high-pressure lines, and the tandem pump. An OEM front active stabilizer bar alone costs €1,500-2,000. Independent specialists can source aftermarket parts and reseal components for significantly less. Some owners choose to disable the system and install conventional anti-roll bars, though this changes the car's handling character.

The E65 is notorious for parasitic battery drain. The car contains dozens of electronic modules that should enter sleep mode when the car is parked. When any module fails to sleep (common culprits: comfort access, MOST bus modules, seat memory), current draw exceeds the normal 50-85 mA threshold and can drain a battery within 2-5 days. Diagnosis requires systematic fuse pulling with a multimeter to identify the offending circuit. The fix depends on which module is at fault. Simple solutions (software update, module replacement) cost €200-500, but complex issues involving multiple modules can reach €800-1,000. A quality battery tender (€50-80) is essential for any E65 that is not driven daily.

At 20+ years old, cooling system components on any E65 are approaching end of life if not already replaced. The electric water pump, thermostat housing, and various hoses and seals degrade over time. A water pump and thermostat replacement together costs €600-1,000 including labor. Coolant hoses and expansion tank add €200-400. If overheating occurs before the owner notices, head gasket or engine damage can follow, pushing costs much higher. Proactive replacement of the entire cooling system is recommended on any E65 that has not had this work done.

The E65 740d uses hydraulic engine mounts that contain fluid-filled chambers for vibration isolation. Over time and mileage, these mounts lose their fluid or the rubber deteriorates, leading to increased vibration at idle and a noticeable clunk when putting the car into drive or reverse. OEM mounts cost €140-200 each, and the car typically needs two. Labor is 3-4 hours due to V8 packaging constraints. Non-OEM mounts made of harder rubber may cost less but often transmit more vibration into the cabin.