The valve cover gasket is a well-documented failure point on the N55. Oil leaks from the gasket can drip onto hot exhaust components and cause misfires when oil enters spark plug wells. Forum data confirms failures as early as 47,000 miles on some units.
The oil filter housing gasket is prone to leaking on the N55, allowing oil and coolant to mix or escape externally. Forum snippets confirm this is a recurring service item, with costs around €1,500 CAD reported for related repairs on BMW platforms.
Oil or coolant leak near oil filter housing
Coolant loss without visible external leak
Oil contamination in coolant
Low oil or coolant warnings
DIY: Moderate
Rod Bearing Wear€1,500-4,000 · 100,000-180,000 kmHIGH
Multiple forum sources report N55 engines seizing due to spun rod bearings at higher mileages. Community mechanics and technicians specifically flag this as a concern beyond 75,000–100,000 km, particularly on unmaintained examples.
The CVV or oil separator can fail on the N55, leading to increased crankcase pressure, oil consumption, and external oil leaks. Forum posts highlight this as a likely cause of excessive oil consumption on the 135is N55 variant.
The N55 is known to consume oil between service intervals. BMW has factory-authorized oil consumption guidelines, but community experience suggests monitoring is essential. Consumption often worsens with a failed CVV or gaskets.
Low oil level between changes
Blue smoke on acceleration
Oil warning light illuminating
DIY: Low
Turbo Coolant Line Rust and Leakage€300-800 · 100,000-180,000 kmMODERATE
Forum data shows turbo coolant lines on N55 platforms can rust and leak, particularly at clamp connections. While reported as less common than some other leaks, neglected examples in salt-belt regions are at higher risk.
Coolant loss
Overheating
Visible rust or wetness around turbo coolant lines
NHTSA recalls cover certain E90/E92 335i models for faulty Takata airbag inflator modules on the driver side. This is a safety recall and must be verified as completed on any used example.
No warning symptoms; risk of inflator rupture in a collision
DIY: Dealer Only
Electrical System Wiring Recall€0-0 · 0-999,999 kmLOW
NHTSA recalls affect 2006–2011 3 Series including 335i for electrical wiring system faults. Verify recall completion status before purchase.
Intermittent electrical faults
Warning lights
DIY: Dealer Only
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Buying Checklist
Run the VIN through NHTSA recall database and confirm all 4 open recalls (especially Takata airbag) are completed
Inspect valve cover gasket area and spark plug wells for oil contamination and evidence of leaks
Check oil filter housing area for oil or coolant staining; request recent OFHG replacement records
Ask for full oil change history and verify intervals were no longer than 8,000–10,000 km using OEM-spec 5W-30 LL-01
Do a cold-start listen for lower-engine knocking that could indicate rod bearing wear
Check coolant level and condition; inspect turbo coolant lines for rust, cracking, or wetness at clamp ends
Service Reality
Community oil interval8,000 km
Oil specificationBMW LL-01 5W-30 fully synthetic
Est. ownership cost (2yr)€1,200–3,500 per year including consumables, oil leaks, and periodic gasket work on a 100,000+ km example
The N55 is a meaningful reliability step up from the N54, but it is not a trouble-free engine — oil leaks from the valve cover and oil filter housing gaskets are a matter of when, not if. Rod bearing wear is a legitimate concern on high-mileage or poorly maintained examples, so full service history is non-negotiable. Budget €800–1,500 upfront for deferred maintenance on any used example and avoid cars with no documented oil change records. If the recalls are unresolved, walk away until the seller can confirm completion.