2004 BMW 645Ci
The 2004 BMW 645Ci marked the return of the 6 Series after a long hiatus, offering a blend of luxury and performance in a stylish coupe and convertible. Its defining characteristic is its elegant design and relatively powerful V8 engine. The primary engine option for the 2004 645Ci is the 4.4L N62B44 V8 engine, producing 325 horsepower and 330 lb-ft of torque. This engine was paired with either a 6-speed manual, 6-speed automatic, or SMG transmission. Owners generally appreciated the car’s sporty handling, luxurious interior, and distinctive styling. Common complaints included electrical gremlins, high maintenance costs, and some reliability concerns related to the engine and transmission.
Engine
4.4L N62B44 V8
- Valve Stem Seal Failure
- Description/Symptoms: Excessive oil consumption, blue smoke from the exhaust upon start-up or after extended idling. This is due to hardened valve stem seals allowing oil to leak into the combustion chamber.
- Solution: Replacement of the valve stem seals. This is a labor-intensive job, often requiring the removal of the cylinder heads.
- Estimated Cost to Fix: $3,000 - $6,000+
- Recalls: None Found
- Coolant Leaks (Valley Pan)
- Description/Symptoms: Coolant leaks from the valley pan located under the intake manifold. This can lead to overheating and coolant loss. The coolant may be visible as a puddle under the car or a sweet coolant smell.
- Solution: Replacement of the valley pan gasket or the entire valley pan assembly. This requires removing the intake manifold.
- Estimated Cost to Fix: $1,500 - $3,000
- Recalls: None Found
- Alternator Bracket Oil Leak
- Description/Symptoms: Oil leak originating from the alternator bracket gasket. This can be difficult to diagnose as the leak may be subtle at first.
- Solution: Replacement of the alternator bracket gasket. Requires removing the alternator and bracket.
- Estimated Cost to Fix: $800 - $1,500
- Recalls: None Found
Transmission
6-Speed Automatic (ZF 6HP26)
- Slipping/Rough Shifting
- Description/Symptoms: Delayed engagement, harsh shifts, slipping between gears, or failure to shift. These problems often stem from degraded transmission fluid, worn solenoids, or issues with the valve body.
- Solution: Transmission fluid flush/replacement (initially, if the fluid is in bad shape, a full replacement is not recommended as it may cause more issues), solenoid replacement, valve body replacement, or complete transmission rebuild/replacement.
- Estimated Cost to Fix: Fluid flush $300 - $500, solenoid replacement $800 - $1,500, valve body replacement $1,500 - $3,000, transmission rebuild/replacement $4,000 - $7,000+
- Recalls: None Found
Suspension
- Active Roll Stabilization (ARS) System Failures
- Description/Symptoms: Warning lights on the dashboard, clunking noises from the suspension, and reduced handling performance. The ARS system uses hydraulic actuators to control body roll. Failures can occur in the hydraulic pump, valve block, or sway bar actuators.
- Solution: Diagnosis of the specific component failure and replacement of the faulty part. This may involve replacing the ARS pump, valve block, sway bar actuators, or hydraulic lines.
- Estimated Cost to Fix: $800 - $2,500+ depending on the component.
- Recalls: None Found
- Control Arm Bushings
- Description/Symptoms: Clunking noises from the front suspension, especially when going over bumps. Poor handling and uneven tire wear.
- Solution: Replacement of the worn control arm bushings.
- Estimated Cost to Fix: $400 - $1,000+
- Recalls: None Found
Electrical
- Battery Drain Issues
- Description/Symptoms: Dead battery overnight or after short periods of inactivity. This can be caused by a variety of factors, including a faulty comfort access module, a failing voltage regulator, or other parasitic drains.
- Solution: Diagnosis of the source of the battery drain and repair/replacement of the faulty component. This may involve testing individual circuits to identify the drain.
- Estimated Cost to Fix: $200 - $1,000+ depending on the source of the drain.
- Recalls: None Found
- iDrive System Malfunctions
- Description/Symptoms: Freezing, slow response times, or complete failure of the iDrive system. This can be caused by software glitches, a faulty control unit, or issues with the display screen.
- Solution: Software update, replacement of the iDrive control unit (CCC), or replacement of the display screen.
- Estimated Cost to Fix: Software update $100 - $300, CCC replacement $800 - $2,000+, display screen replacement $500 - $1,500+
- Recalls: None Found
- Comfort Access Issues
- Description/Symptoms: Intermittent or complete failure of the comfort access system, which allows keyless entry and start. This can be caused by faulty door handles, a failed comfort access module, or wiring issues.
- Solution: Diagnosis of the specific component failure and replacement of the faulty part. This may involve replacing door handles, the comfort access module, or repairing wiring.
- Estimated Cost to Fix: $300 - $1,500+ depending on the component.
- Recalls: None Found
Exterior
- Convertible Top Issues (Convertible Models)
- Description/Symptoms: Failure of the convertible top to open or close properly, error messages on the dashboard, hydraulic leaks, and mechanical binding.
- Solution: Diagnosis of the specific issue and repair or replacement of the faulty components. This may involve repairing or replacing hydraulic cylinders, hoses, sensors, or the convertible top motor.
- Estimated Cost to Fix: $500 - $3,000+ depending on the complexity of the repair.
- Recalls: None Found
Interior
- Seat Motor Failure
- Description/Symptoms: The seat motor stops working, preventing the seat from moving.
- Solution: Replace the seat motor.
- Estimated Cost to Fix: $300 - $800+
- Recalls: None Found
Summary
The 2004 BMW 645Ci, while stylish and enjoyable to drive, presents owners with a range of potential issues. Engine problems, particularly valve stem seal failure and coolant leaks, can be quite costly to address. Transmission issues, especially with the automatic transmission, can also be expensive to repair. Electrical gremlins are common, and suspension issues can affect handling and ride quality. Overall, potential buyers should be aware of these common problems and factor in potential maintenance costs when considering the purchase of a 2004 BMW 645Ci. Pre-purchase inspections by a qualified BMW mechanic are highly recommended.