2004 MERCEDES-BENZ C240 W203

Typical onset: 80,000-150,000 mi

Symptoms: Metallic rattling or knocking from front of engine at idle or low RPM, Metal shavings in oil filter and on magnetic drain plug, Check engine light with camshaft position sensor codes (P0340/P0345), Sudden catastrophic failure—loss of oil pressure, seized engine

Fix: The M112 balance shaft gears wear prematurely, sending metal through the entire oiling system. Once contamination occurs, bearings (mains, rods, cam) are compromised. Repair requires complete teardown: new balance shaft assembly, all bearings, machine work on crank/block if scored. Many shops recommend short block or used engine swap due to labor economics. Figure 25-35 hours labor plus parts.

Estimated cost: $4,500-8,000

Typical onset: 70,000-120,000 mi

Symptoms: Pink or red fluid dripping near front of engine/under radiator, Transmission fluid level dropping, topped off repeatedly, Harsh shifting or delayed engagement if fluid level gets low, Burnt transmission smell if run low for extended period

Fix: The quick-connect fittings at the radiator end tank crack or the internal cooler develops pinholes. Some techs replace just the lines (~3 hours), but smart move is radiator replacement since the internal cooler often fails simultaneously. Includes fluid flush and refill with 236.14 spec fluid.

Estimated cost: $800-1,400

Typical onset: 60,000-140,000 mi

Symptoms: No-start condition with cranking but no ignition, Intermittent stalling while driving, restarts after cooling, Check engine light with P0335 or P0385 code, Loss of tachometer reading during failure event

Fix: Sensor mounted on bell housing fails from heat cycling. Requires raising engine slightly or working from underneath with transmission crossmember dropped for access. Quality OE sensor critical—aftermarket failures common. 2-3 hours labor.

Estimated cost: $350-550

Typical onset: 90,000-160,000 mi

Symptoms: Harsh 2-3 or 3-4 shifts, especially when cold, Limp mode—stuck in 2nd or 3rd gear with warning light, Erratic shifting patterns, flaring between gears, Multiple transmission control codes stored

Fix: The 722.6 five-speed auto's internal wiring harness (conductor plate) and solenoids fail. Requires pan drop, valve body removal, plate and filter replacement, plus software adaptation. If caught early, prevents clutch damage. 6-8 hours labor. Use genuine Mercedes parts—remanufactured plates fail quickly.

Estimated cost: $1,200-2,000

Typical onset: 80,000-130,000 mi

Symptoms: Clunking when shifting from park to drive or reverse, Vibration at idle in gear that disappears in neutral, Visible engine rocking during throttle blips, Accelerated wear on exhaust hangers and halfshaft boots

Fix: Hydraulic engine mounts deteriorate, allowing excessive drivetrain movement. Front mount most critical. Right mount (near timing cover) also common. Replace as a set for best results. 3-4 hours labor depending on which mounts.

Estimated cost: $600-1,000

Typical onset: 70,000-150,000 mi

Symptoms: Rough idle, intermittent stalling at stop lights, Hesitation or flat spot during acceleration, Poor fuel economy—dropping 3-5 MPG, Check engine light with P0100, P0102, or P0103 codes

Fix: Hot-wire MAF sensor fouls from oil mist or debris. Clean with MAF cleaner first (sometimes works temporarily), but usually requires replacement. Some techs see reoccurrence if crankcase ventilation system clogged. 0.5 hour labor.

Estimated cost: $200-400

Symptoms: Window drops into door with loud crack or won't roll up, Grinding or clicking noise during window operation, Window moves slowly or binds in one section of travel, One-touch auto function stops working

Fix: Plastic carrier clips and regulator mechanism fail. Front windows far more common than rears. Requires door panel removal, regulator replacement. OEM regulators include motor; aftermarket motors often fail quickly. 2 hours per door labor.

Estimated cost: $350-600