2004 PORSCHE 911

Typical onset: 40,000-80,000 mi

Symptoms: Metal shavings in oil during changes, Rattling or knocking from engine at startup, Sudden loss of oil pressure, Complete engine seizure without warning in worst cases

Fix: IMS bearing is buried in the engine between the crankshaft and transmission. Preventive replacement requires transmission removal (12-16 hours labor). If it fails, you're looking at complete engine rebuild or replacement. Many owners do this preventively during clutch jobs. 2004 models have the larger, slightly more robust bearing than earlier 996s, but failure still happens.

Estimated cost: $2,500-4,000 preventive replacement; $15,000-25,000 if engine damage occurs

Typical onset: 60,000-100,000 mi

Symptoms: Blue smoke on cold startup that clears after warm-up, Excessive oil consumption (more than 1 qt per 1,000 mi), Loss of compression in one or more cylinders, Rough idle when cold

Fix: The M96 engine uses Lokasil-coated aluminum cylinders that can score due to cold starts, low oil, or poor break-in. Only fix is complete engine rebuild with new cylinders and pistons (40-50 hours), or short block replacement. Borescope inspection during pre-purchase is critical. 3.6L engines slightly more prone than 3.4L.

Estimated cost: $18,000-28,000

Typical onset: 50,000-90,000 mi

Symptoms: Oil drips or puddles under engine/transmission area, Oil spots on garage floor after sitting overnight, Visible oil coating on rear of engine and bell housing, Oil smell in cabin after highway driving

Fix: The rear main seal between engine and transmission develops leaks from age and heat cycles. Requires transmission removal to access (10-14 hours). Most owners wait until doing IMS bearing or clutch work to address all three simultaneously, since labor overlaps. Not dangerous but messy and will eventually consume significant oil.

Estimated cost: $1,800-2,800 standalone; $600-900 parts/labor added to clutch or IMS job

Typical onset: 70,000-120,000 mi

Symptoms: Visible cracks in plastic coolant reservoir, Coolant smell in engine bay, Coolant level drops frequently, Puddles of coolant under vehicle after sitting

Fix: The plastic expansion tank becomes brittle over time and develops cracks, usually at mounting points or seams. Easy DIY fix (1-2 hours) but can leave you stranded if it fails completely and overheats the engine. Check carefully during pre-purchase inspection. Replace proactively if original tank shows any stress marks.

Estimated cost: $200-400

Typical onset: 80,000-130,000 mi

Symptoms: Transmission fluid leaking from front of car, Pink/red fluid on ground (not oil), Transmission slipping or delayed shifts after highway driving, Low transmission fluid warnings

Fix: Tiptronic models have metal cooler lines that corrode from road salt and moisture, particularly at crimped connections. Lines run to front-mounted cooler and can fail suddenly. Replacement requires removing front bumper and splash shields (4-6 hours). Manual transmission cars don't have this issue. Check all Tiptronics carefully for weeping around cooler area.

Estimated cost: $1,200-2,000

Typical onset: 60,000-100,000 mi

Symptoms: Clunking over bumps from front end, Wandering or vague steering feel, Uneven tire wear on inside edges, Vehicle pulls to one side

Fix: Front control arm bushings wear and crack, especially on cars driven in cold climates or on rough roads. Porsche sells complete control arm assemblies rather than individual bushings. Replace both sides simultaneously for even handling (3-5 hours). Aftermarket polyurethane options available but harsher ride.

Estimated cost: $1,000-1,800 both sides

Typical onset: 70,000-110,000 mi

Symptoms: Excessive white smoke from exhaust (not coolant-related), Oil consumption increases dramatically, Oil in intake manifold or throttle body, Check engine light for lean/rich codes

Fix: The air-oil separator diaphragm tears, allowing crankcase pressure to force oil into the intake system. Engine burns this oil, creating smoke and fouling. Located under intake manifold, requires significant disassembly (6-8 hours). Failure can cause catalytic converter damage if ignored. More common on cars with frequent short trips.

Estimated cost: $1,400-2,200