2004 CHEVROLET IMPALA SS

Typical onset: 80,000-120,000 mi

Symptoms: Coolant leaks at front of engine, Overheating, White smoke from exhaust on cold start, Coolant loss with no visible external leak, Rough idle when cold

Fix: Replace lower intake manifold gaskets (Fel-Pro 1200 kit preferred). Requires removing supercharger, fuel rails, and upper plenum. 6-8 hours labor. Also replace thermostat and coolant elbows while you're in there.

Estimated cost: $800-1,400

Typical onset: 100,000-150,000 mi

Symptoms: Loud knocking on cold start that quiets with oil pressure, Metallic rapping that increases with RPM, Low oil pressure warning, Metal shavings in oil during changes, Sudden catastrophic failure with no warning in some cases

Fix: L67 Series II engines have undersized rod bearings from factory. Once knocking starts, you need crank polishing, new bearings, and rod inspection minimum (8-12 hours). Often progresses to full rebuild with pistons and rings when machine work is needed. Many opt for 0.001" oversize bearings as preventive measure.

Estimated cost: $2,500-5,500

Typical onset: 90,000-140,000 mi

Symptoms: Transmission fluid leaking near radiator, Pink fluid dripping under front of car, Transmission slipping or delayed engagement, Milky appearance in transmission fluid (coolant contamination), Overheating transmission

Fix: Steel lines corrode where they attach to radiator. Replace both cooler lines and external filter. If coolant mixed with ATF, flush cooler and possibly rebuild transmission. Lines alone: 2-3 hours. With transmission damage: add 12-18 hours for rebuild.

Estimated cost: $300-600 (lines only), $2,000-3,500 (if transmission contaminated)

Typical onset: 70,000-110,000 mi

Symptoms: Clunking when shifting from Park to Drive/Reverse, Vibration at idle in gear, Visible engine movement when accelerating, Transmission jerking on hard acceleration

Fix: Rear transmission mount deteriorates from heat and torque stress. Replace transmission mount and inspect torque strut mounts. 1.5-2 hours labor. Use OEM or upgraded polyurethane mount.

Estimated cost: $200-350

Typical onset: 90,000-130,000 mi

Symptoms: Whining or squealing from supercharger, Loss of boost and power, Check engine light with MAF/fuel trim codes, Rubber debris in intake, Supercharger spinning freely without resistance

Fix: Rubber coupler between supercharger snout and input shaft deteriorates. Replace coupler and inspect snout bearing. 4-5 hours labor. While apart, check snout bearing play and consider rebuild if loose.

Estimated cost: $400-800 (coupler), $1,200-2,000 (full supercharger rebuild)

Typical onset: 120,000-180,000 mi

Symptoms: External coolant leaks at head/block junction, Overheating, Rough running and misfire, Exhaust gases in coolant reservoir, Rapid coolant loss

Fix: Gaskets fail from age and repeated heat cycles. Requires removing supercharger, fuel system, and both heads. Resurface heads, new bolts required. 12-16 hours labor. Often combined with lower intake gaskets if not already done.

Estimated cost: $2,200-3,800

Typical onset: 100,000-150,000 mi

Symptoms: Hard starting, especially when hot, Loss of power under boost, Fuel smell from engine bay, Check engine light with fuel trim codes, Stalling at idle or during acceleration

Fix: In-tank pump wears or pressure regulator on fuel rail leaks. Tank drop for pump: 3-4 hours. Regulator replacement: 2 hours. Always replace fuel filter during pump work (external frame-mount canister).

Estimated cost: $500-900 (pump), $250-450 (regulator)