The 2004 RSX is a solid Honda K-series platform with excellent reliability potential, but certain examples suffer catastrophic K20 engine failures from oil starvation or abuse, and second gear synchro wear is the Achilles heel of the manual transmission.
Second Gear Synchro Failure (Manual Transmission)
Common · medium severityTypical onset: 80,000-150,000 mi
Symptoms: grinding or crunching into second gear, difficulty engaging second when shifting quickly, popping out of second under load
Fix: Requires transmission removal and internal rebuild with new synchro rings, hub, and sleeve. Approximately 8-10 hours labor for R&R plus internal work. Some shops replace entire transmission with used unit to save labor cost.
Estimated cost: $1,800-3,200
K20 Piston Ring Failure / Oil Consumption
Occasional · high severityTypical onset: 100,000-180,000 mi
Symptoms: burning one quart or more per 1,000 miles, blue smoke on startup or acceleration, fouled spark plugs, catastrophic failure if oil level drops critically low
Fix: Oil ring land cracks or excessive ring wear require full engine rebuild or short block replacement. 18-24 hours labor for removal, teardown, machining (if salvageable), reassembly, and reinstall. Many opt for used low-mileage K20A2/A3 swap.
Estimated cost: $3,500-6,500
Crankshaft Position Sensor Failure
Common · high severityTypical onset: 90,000-140,000 mi
Symptoms: no-start condition with cranking but no spark, intermittent stalling when hot, CEL with P0335 or P0339 codes
Fix: Sensor is behind timing cover, requires accessory belt removal and partial timing cover access. 1.5-2.5 hours labor depending on familiarity. Sensor itself is cheap ($50-90), labor drives cost.
Estimated cost: $200-400
Transmission Mount Collapse
Common · low severityTypical onset: 70,000-120,000 mi
Symptoms: excessive driveline clunk on throttle application, shifter vibration at idle, visible sagging of transmission when inspected from below
Fix: OEM rubber mounts wear out from spirited driving and engine torque. Replacement requires supporting transmission from below, unbolting mount bracket. 1-1.5 hours labor. Upgrade to polyurethane aftermarket mounts common.
Estimated cost: $150-300
Headlight Low Beam Failure / Wiring Harness Melt
Occasional · medium severitySymptoms: one or both low beams intermittent or dead, burnt smell from headlight area, melted connector at bulb socket, high beams still functional
Fix: Factory halogen wiring undersized for bulb draw, especially with aftermarket high-wattage bulbs. Connector melts at bulb socket. Repair involves cutting out damaged section and splicing in heavier gauge wire or installing relay harness. 1-2 hours labor depending on damage extent.
Estimated cost: $100-250
Fuel Filter Clogging (Early Symptoms)
Occasional · medium severityTypical onset: 120,000+ mi
Symptoms: hesitation or stumble under hard acceleration, fuel pump whine becomes louder, loss of top-end power, lean codes if severe
Fix: In-tank fuel filter often neglected as it's not a standard service item in owner's manual. Requires fuel tank drop or pump access through rear seat area depending on tech preference. 2-3 hours labor including tank drop if needed. Replacement of entire pump assembly common since filter not sold separately by Honda.
Estimated cost: $400-700
Valve Cover Gasket and Spark Plug Tube Seal Leaks
Common · low severityTypical onset: 100,000+ mi
Symptoms: oil pooling in spark plug wells, burning oil smell from engine bay, minor oil seepage visible on valve cover perimeter, potential misfire if oil floods plug wells
Fix: Typical Honda K-series maintenance item. Valve cover removal, old gasket and tube seals replaced. 2-3 hours labor including cleaning surfaces and reinstalling with proper torque sequence. Replace PCV valve at same time.
Estimated cost: $300-500
Buy one with documented maintenance history and a healthy manual transmission—avoid examples with oil consumption or second-gear issues unless you're prepared for $2k-6k in repairs.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.