The 2008 BMW 335i, part of the E90/E92 generation, is a thrilling sport sedan with serious performance capabilities, thanks to its twin-turbocharged N54 engine. But as impressive as it is to drive, the 335i is equally infamous for a range of mechanical and electrical issues—many of which can be expensive if not addressed early. This guide outlines the most common problems with the 2008 BMW 335i, how to spot them, and what to expect when it comes to repairs.
Is the 2008 BMW 335i Reliable?
The 2008 BMW 335i offers solid performance but is not the most reliable in its class, largely due to the complexity of the N54 engine and its associated systems. Owners often describe it as rewarding to drive but demanding to own. Reliability improves significantly with proactive maintenance and updated replacement parts.
Common 2008 BMW 335i Problems
1. High Pressure Fuel Pump (HPFP) Failure
The HPFP is one of the most notorious issues in the early N54-powered BMWs, especially between 2007 and 2010 models.
- Symptoms: Long crank times, engine misfires, hesitation, limp mode
- Fix: Replace HPFP (revised units available with better durability)
- Cost: $900–$1,500
2. Turbocharger Wastegate Rattle
The factory turbos often develop loose wastegate arms, which rattle and eventually cause boost issues.
- Symptoms: Rattling noise at idle or deceleration, underboost codes, loss of power
- Fix: Replace turbos or install upgraded wastegate arms (if caught early)
- Cost: $2,000–$3,500 for full turbo replacement
3. Fuel Injector Failure
The piezo-style injectors in the N54 are prone to leaking and causing unburnt fuel to reach the oil system.
- Symptoms: Misfires, rough idle, black smoke from exhaust, fuel odor
- Fix: Replace injectors with updated “Index 12” versions
- Cost: $250–$400 per injector; often done as a set
4. Water Pump and Thermostat Failure
The electric water pump fails suddenly, often without warning, and can cause immediate overheating.
- Symptoms: Coolant warning lights, overheating, fan running at full speed
- Fix: Replace pump and thermostat together
- Cost: $800–$1,200
5. Oil Filter Housing Gasket (OFHG) Leak
This common oil leak can cause oil to drip onto the serpentine belt, leading to belt failure or worse.
- Symptoms: Oil leaks around the oil filter housing, low oil levels
- Fix: Replace oil filter housing gasket
- Cost: $300–$600
6. Carbon Buildup on Intake Valves
The N54 uses direct injection, which means fuel doesn’t wash over the intake valves—leading to carbon buildup over time.
- Symptoms: Loss of power, rough idle, poor throttle response, misfires
- Fix: Walnut blasting of intake valves
- Cost: $400–$700
7. Valve Cover and Gasket Leaks
Plastic valve covers on the N54 can crack or warp, causing oil to leak onto the engine.
- Symptoms: Oil smell, smoke from engine bay, visible oil on the valve cover
- Fix: Replace valve cover and gasket
- Cost: $400–$800
8. Ignition Coil and Spark Plug Failure
Misfires are common with older coils and plugs, especially on tuned or high-mileage cars.
- Symptoms: Engine shaking, misfires under load, check engine light
- Fix: Replace coils and plugs every 50,000–60,000 miles
- Cost: $200–$400
9. Transmission Issues (ZF 6HP Automatic)
The automatic transmission is durable but can develop issues if fluid is never changed (despite BMW’s “lifetime” claim).
- Symptoms: Rough shifting, hesitation, gear slip
- Fix: Fluid service or software update; rebuild if damage is advanced
- Cost: $400–$600 for service; $3,000+ for rebuild
10. Battery and IBS Sensor Failures
The Intelligent Battery Sensor (IBS) can malfunction and shut down accessories or cause no-start conditions.
- Symptoms: Electrical malfunctions, low voltage warnings, hard starting
- Fix: Replace IBS sensor or battery, register battery afterward
- Cost: $250–$400
Known Recalls and Service Bulletins
- HPFP Recall: BMW extended warranty coverage to 10 years/120,000 miles for HPFP issues
- Turbo Wastegate Bulletin: Service bulletin covering wastegate rattle and turbo replacements in some cases
- Battery Cable Recall: Positive cable connection may come loose and cause power failure
Typical Repair Costs
| Problem | Estimated Repair Cost |
|---|---|
| HPFP Replacement | $900–$1,500 |
| Turbo Replacement | $2,000–$3,500 |
| Fuel Injector Set | $1,000–$1,500 |
| Water Pump & Thermostat | $800–$1,200 |
| Oil Filter Housing Gasket | $300–$600 |
| Walnut Blasting | $400–$700 |
| Valve Cover & Gasket | $400–$800 |
Maintenance Tips to Prevent Major Issues
- Change engine oil every 5,000 miles with high-quality synthetic
- Replace HPFP and injectors with updated versions
- Walnut blast intake valves every 50,000–60,000 miles
- Change spark plugs and coils proactively
- Flush and replace transmission fluid every 60,000–70,000 miles
- Use a BMW-specific OBD tool for accurate diagnostics (like INPA or ISTA)
Final Thoughts
The 2008 BMW 335i delivers serious performance, premium features, and a driving experience few cars in its class can match. But it comes at a cost—both financially and in terms of maintenance demands. Common problems like HPFP failure, turbo issues, oil leaks, and injector malfunctions are all well-known in the BMW community.
Thinking of owning one? Budget for repairs, stay ahead on maintenance, and only buy a 335i with a strong service history. Treated properly, this car can offer years of thrilling, dependable performance.