2004 MERCEDES-BENZ CLK320 C209

Typical onset: 80,000-150,000 mi

Symptoms: Sudden metallic rattling or knocking from engine, Check engine light with cam/crank correlation codes, Catastrophic engine failure—metal shavings throughout oil system, Often no warning until complete failure

Fix: The plastic balance shaft gear strips teeth and destroys the timing chain, sending debris through the entire engine. Requires complete engine rebuild or replacement—short block minimum, often full long block. 20-30 labor hours for engine removal, teardown, and reinstall.

Estimated cost: $4,500-8,000

Typical onset: 90,000-140,000 mi

Symptoms: Transmission fluid seeping from bell housing area, Pink or red fluid spots under vehicle, Low transmission fluid level, Harsh shifts if fluid gets too low

Fix: The 722.6 5-speed auto has a cooler seal at the front that hardens and leaks. Requires transmission removal to replace seal and often the cooler lines. 8-10 hours labor plus flush and refill with Mercedes-spec ATF.

Estimated cost: $1,200-1,800

Typical onset: 70,000-120,000 mi

Symptoms: Clunk when shifting from Park to Drive or Reverse, Vibration at idle in gear, Excessive driveline movement during acceleration, Visible sag or fluid leak from rubber mount

Fix: The rear transmission mount fails from age and fluid contamination. Straightforward replacement—support transmission, unbolt old mount, install new. 1.5-2 hours labor.

Estimated cost: $300-500

Typical onset: 60,000-100,000 mi

Symptoms: Oil consumption increases, Rough idle or hesitation, Oil leaks from valve covers or front/rear main seals, Whistling noise from engine bay, Check engine light for lean/rich codes

Fix: The CCV valve and hoses clog with oil sludge, causing crankcase pressure that blows out seals. Replace CCV valve, breather hoses, and intake boot. Often need valve cover gaskets while in there. 3-4 hours labor.

Estimated cost: $600-1,000

Symptoms: Window drops into door, Slow or jerky window operation, Clicking or grinding noise when operating window, Window won't go up or down

Fix: The window regulator plastic clips break or the motor fails. Common Mercedes issue. Requires door panel removal and regulator replacement. 2-3 hours per side.

Estimated cost: $400-700

Symptoms: Red brake warning light and multiple warning messages, STOP VEHICLE SEE OPERATOR'S MANUAL message, Hard brake pedal with reduced braking power, ABS and ESP lights illuminated

Fix: If equipped with SBC (Sensotronic Brake Control), the hydraulic pump unit fails and Mercedes issued recalls. Replacement is dealer-only with expensive remanufactured unit. 4-6 hours labor. Many have been retrofitted to conventional ABS under recall.

Estimated cost: $2,000-3,500

Typical onset: 100,000-150,000 mi

Symptoms: Fuel smell in cabin or near fuel tank, Check engine light with fuel trim or pressure codes, Hard starting or stumbling under load, Visible fuel staining on tank

Fix: Fuel pump fails or the in-tank sealing ring cracks. Requires fuel tank drop, pump replacement, and new seals. 4-5 hours labor, must dispose of fuel properly.

Estimated cost: $800-1,400