2004 BMW 745i

The 2004 BMW 745i is a luxury sedan known for its innovative technology and powerful performance. It came equipped with a 4.4L V8 engine, producing 325 horsepower and 330 lb-ft of torque. While the 745i offers a comfortable ride and advanced features for its time, it is also known for its complex systems that can lead to reliability issues as it ages. Owners often praise its smooth ride and powerful engine, but dislike its high maintenance costs and complicated electronics. All 2004 BMW 745i’s came with a 6-speed automatic transmission.

Engine

4.4L N62 V8

• Valve Stem Seal Failure
  • Description/Symptoms: Excessive oil consumption, blue smoke upon start-up, especially after sitting for extended periods. This is due to the valve stem seals hardening and cracking over time, allowing oil to leak into the combustion chamber while the engine is off.
  • Solution: Replacement of valve stem seals. This is a labor-intensive job that often involves removing the cylinder heads.
  • Estimated Cost to Fix: $3,000 - $5,000+
• Coolant Leaks (Valley Pan)
  • Description/Symptoms: Coolant leaks often originating from the “valley pan” located beneath the intake manifold. This pan houses coolant passages and tends to corrode over time, leading to leaks. Visible coolant loss, overheating, and a sweet coolant smell are common symptoms.
  • Solution: Replacement of the valley pan and related gaskets. This requires significant disassembly of the top end of the engine.
  • Estimated Cost to Fix: $1,500 - $3,000+
• Alternator Bracket Oil Leaks
  • Description/Symptoms: Oil leaks originating from the alternator bracket, which is mounted to the engine block. The gaskets and seals on this bracket can degrade, allowing oil to leak.
  • Solution: Replacement of the alternator bracket gasket and seals.
  • Estimated Cost to Fix: $500 - $1,000
• Vacuum Leaks
  • Description/Symptoms: Rough idling, decreased engine performance, and possible error codes related to lean fuel trims. Vacuum leaks can occur from various hoses and intake manifold gaskets.
  • Solution: Smoke test to identify the leaks, then replace the affected hoses and gaskets.
  • Estimated Cost to Fix: $200 - $800+ depending on the location and complexity of the leak.

Transmission

6-Speed Automatic (ZF 6HP26)

• Slipping/Harsh Shifting
  • Description/Symptoms: The transmission exhibits slipping between gears, harsh or delayed shifts, or failure to shift properly. These symptoms are often caused by worn valve body components, low fluid level, or degraded transmission fluid.
  • Solution: Start with a transmission fluid and filter change, ensuring the correct fluid type is used. If the problem persists, the valve body may need to be rebuilt or replaced. In severe cases, a complete transmission rebuild or replacement might be necessary.
  • Estimated Cost to Fix: $300 (fluid/filter change) to $5,000+ (rebuild/replacement)
• Mechatronic Sleeve Leaks
  • Description/Symptoms: Transmission fluid leaks originating from the mechatronic sleeve, which is the electrical connector that passes through the transmission housing. This can cause a loss of fluid pressure and lead to shifting problems.
  • Solution: Replacement of the mechatronic sleeve and fluid refill.
  • Estimated Cost to Fix: $300 - $600

Suspension

• Air Suspension Compressor Failure
  • Description/Symptoms: The air suspension system fails to maintain the correct ride height, leading to the car sitting low or unevenly. This is often caused by a failing air compressor, which is responsible for providing air pressure to the system.
  • Solution: Replacement of the air suspension compressor. Also inspect for leaks in the air struts and lines.
  • Estimated Cost to Fix: $800 - $1,500+
• Air Strut Leaks
  • Description/Symptoms: The air struts develop leaks, causing the air suspension system to lose pressure and the car to sag. These leaks can be caused by age and wear of the air bladders within the struts.
  • Solution: Replacement of the leaking air struts. It is often recommended to replace them in pairs.
  • Estimated Cost to Fix: $1,000 - $2,500+ per pair

Electrical

• iDrive System Malfunctions
  • Description/Symptoms: The iDrive system, which controls many of the car’s functions, experiences glitches, freezes, or complete failure. This can affect navigation, audio, climate control, and other features.
  • Solution: Software updates may resolve some issues. In other cases, the iDrive controller or display screen may need to be replaced.
  • Estimated Cost to Fix: $200 (software update) to $1,500+ (component replacement)
• Battery Drain Issues
  • Description/Symptoms: The battery drains quickly, especially when the car is parked. This can be caused by a parasitic draw from a faulty module or accessory.
  • Solution: Diagnose the source of the parasitic draw using a multimeter. Disconnect items one by one to find the source. Repair or replace the faulty module or component.
  • Estimated Cost to Fix: $100 - $1,000+ depending on the complexity of the issue.
• Comfort Access Problems
  • Description/Symptoms: The comfort access system fails. This causes the remote to not open the door, or the vehicle not start.
  • Solution: Test all components of the comfort access system and replace the components not working correctly.
  • Estimated Cost to Fix: $300 - $1,000+

Exterior

• Tail Light Failure
  • Description/Symptoms: One or more of the tail lights fail to function properly, including brake lights, turn signals, and running lights. This can be caused by bulb failure, wiring issues, or a faulty light control module.
  • Solution: Check bulbs first. If bulbs are good, trace the wiring to identify any shorts or breaks. If the wiring is intact, the light control module may need to be replaced.
  • Estimated Cost to Fix: $20 - $500+

Interior

• Sunroof Problems
  • Description/Symptoms: The sunroof fails to open or close properly, gets stuck, or makes excessive noise. This can be caused by a faulty motor, damaged tracks, or debris obstructing the mechanism.
  • Solution: Inspect the sunroof tracks for debris and lubricate them. If the motor is faulty, it may need to be replaced. In severe cases, the entire sunroof assembly may need to be replaced.
  • Estimated Cost to Fix: $50 - $1,000+
• Door Lock Actuator Failure
  • Description/Symptoms: The door lock actuator fails, making it impossible to lock or unlock the door using the remote or the interior switch.
  • Solution: Replacement of the faulty door lock actuator.
  • Estimated Cost to Fix: $200 - $500

Recalls:

• 05V369000
• 05V487000
• 06V207000
• 07V355000
• 07V458000
• 13V074000

Summary

The 2004 BMW 745i, while offering a luxurious driving experience, is prone to various mechanical and electrical issues as it ages. Engine issues such as valve stem seal failure and coolant leaks are relatively common and can be expensive to repair. Transmission problems, particularly slipping and harsh shifting, also pose a significant concern. Electrical issues with the iDrive system and battery drain can be frustrating for owners. The air suspension is another area where problems often arise. Overall, owning a 2004 BMW 745i requires a commitment to maintenance and a willingness to address potential issues, which can be costly.