Porsche 911 996 Targa

All 996 Targas were produced from 2002-2005 and use the single-row IMS bearing, which has an estimated lifetime failure rate of around 8-10%. The bearing supports the intermediate shaft that drives the camshafts. When it fails, metal debris circulates through the engine, blocking oil passages and causing severe internal damage. There is no predictable mileage pattern - failures have occurred from 20,000 km to over 200,000 km. Preventive IMS bearing upgrade costs €1,500-2,500 (parts + 10-14 hours labour). If the bearing fails before replacement, budget €8,000-15,000 for an engine rebuild or replacement. Regular use and frequent oil changes with quality oil reduce the failure risk. Verifying whether the IMS bearing has already been upgraded is the single most important pre-purchase check.

The M96 engine uses an open-deck crankcase with Lokasil/Alusil cylinder linings. Under thermal and mechanical stress, cylinder 6 runs hottest and distorts slightly, causing the piston to contact the liner and initiate progressive scoring. Symptoms include a rhythmic metallic ticking at cold idle, rising oil consumption, and sooty exhaust on the driver's side. A bore scope inspection before purchase is essential - any qualified Porsche specialist can perform this for €100-200. If scoring is found, repair requires machining the case and fitting Nickies aluminium sleeves with forged pistons, costing €5,000-6,000 for the cylinder work alone. Including engine removal and rebuild, expect €10,000-15,000 total. Shorter oil change intervals (every 8,000 km or annually) and a slightly heavier oil grade help reduce the risk.

The 996 Targa uses a sliding glass roof with metal drive cables, an electric motor, and numerous microswitches. Specialists report more than 70 cable replacements on 996/997 Targa models alone. Common failures include stretched or jammed cables, worn corner tubes, broken microswitches in the rear hatch mechanism, and clogged drain tubes that can flood the cabin. Lubricating the drive cables with oil or grease is a well-known mistake that attracts dust and debris, eventually seizing the mechanism. A full cable and tube refurbishment at a Porsche specialist runs €1,500-3,000. Rear hatch motor or microswitch repair is typically €400-900. Drain tube cleaning should be done twice a year. Roof creak and squeak is considered a characteristic rather than a fault - there is no permanent cure. Always test the roof and hatch through a full open/close cycle before buying.

The rear main seal sits where the crankshaft exits the engine block to meet the clutch and gearbox. Porsche revised this seal several times during M96 production without fully resolving the issue. When it fails, oil leaks onto the flywheel and clutch, and in severe cases the clutch friction material becomes contaminated. The seal itself costs under €50, but the gearbox must be removed for access (6-8 hours labour). Most specialists combine RMS replacement with clutch replacement and IMS bearing upgrade because the gearbox is already out. Standalone RMS replacement costs €1,200-1,800; combined with clutch work expect €2,000-3,500 total.

The AOS links the crankcase to the intake manifold to recirculate blow-by gases. Over time the internal diaphragm degrades, allowing liquid oil to be drawn into the intake. Mild failure causes a hunting idle, higher oil consumption, and slight blue smoke. Severe failure produces dramatic white smoke clouds from the exhaust. The part itself costs €100-150, but access requires 3-4 hours of labour. Total replacement cost is €400-800 at a specialist. Always use genuine Porsche parts - aftermarket AOS units are known to fail quickly. AOS failure can also contribute to bore scoring by leaning out the fuel mixture on one bank, so prompt replacement is important.

The Targa has several rubber seals around the rear glass hatch and the sliding roof perimeter. The outer rear window seal peels off without adhesive and simply press-fits into the channel, so it can loosen or tear over time. Water ingress shows as damp carpets, misting windows, or puddles in the rear luggage well. A Porsche dealer quote for replacing Targa roof and window seals is approximately £900 (around €1,050). The outer rear window seal part itself is approximately €80; DIY replacement with silicone lubricant is feasible. Interior dampness also accelerates corrosion of electrical connectors under the carpets.

The plastic coolant expansion tank becomes brittle with age and thermal cycling. After 8-10 years, hairline cracks develop that may only weep under pressure, making diagnosis difficult. The plastic elbow pipes running to the oil cooler also have thin walls near the O-ring seal that crack over time. Small puddles behind the car or a slowly dropping coolant level are typical symptoms. Porsche's labour time on the expansion tank is 5.5 hours including coolant fill and bleed. Parts cost €100-250, total repair €400-900. Elbow pipe replacement adds €200-400. Unnoticed coolant loss can cause overheating, head gasket damage, or accelerate bore scoring. Preventive replacement is recommended on any 996 still running original cooling system plastics.

The M96 water pump uses a plastic impeller that weakens through thermal cycling until individual blades break off. Fragments travel through the cooling system and can block passages in the cylinder heads, creating localised hot spots that accelerate bore scoring. Symptoms include gradual coolant temperature rise, especially in traffic, and poor cabin heating. Replacement with an updated pump (aftermarket metal impeller available) is recommended every 60,000-80,000 km or 5 years. Parts cost €100-200, labour 2.5-3.5 hours. Total cost at a specialist: €500-1,000. Given the potential for cascading damage from overheating, this is one of the more worthwhile preventive replacements on the 996.

All 996 Targas are now 20+ years old and exhaust corrosion is increasingly common. Rust at connection points creates exhaust leaks that trigger check engine lights. The main exhaust header pipe leading to the catalytic converter can crack and fail completely. Catalytic converter replacement is the most expensive component at €1,500-2,500 per side for OEM units, though aftermarket alternatives exist for €600-1,200. Complete exhaust system replacement including upgraded sports cats and silencers costs €2,000-3,000. Repair of individual corroded sections runs €800-1,500.