Porsche Cayman S 3.4 987

The 3.4L M97.21 engine in the 987.1 Cayman S is susceptible to bore scoring, where vertical scratch marks develop on the cylinder walls. This is caused by the Lokasil cylinder liner material combined with tight piston clearances and potential issues with the cooling system design. The 3.4L displacement is more affected than the smaller 2.7L engines due to larger bore diameter. Symptoms include increased oil consumption, light tapping or knocking sounds, and eventually visible blue smoke. A borescope inspection is the only reliable way to detect early scoring. Repair requires an engine rebuild with new cylinders and pistons, costing €8,000-12,000 at a European specialist. The 987.2 DFI engine (9A1) used revised piston and bore coatings that significantly reduced this issue, though it can still occur on a small number of cars.

The 987.1 Cayman S (2006-2008) uses a single-row IMS bearing that supports the intermediate shaft driving the camshafts. Failure rate on 2006-2008 models with the larger bearing design is estimated at around 1% or less, significantly lower than the 8-10% seen on earlier 986/996 models. However, if the bearing does fail, metal debris contaminates the oil and can destroy the engine. Preventive replacement costs €1,500-2,500 when done alongside a clutch job (since the transmission must be removed for access). If the bearing fails and damages the engine, repair costs can reach €10,000+. The 987.2 (2009-2012) eliminated the IMS bearing entirely with its new 9A1 engine design. LN Engineering and other aftermarket suppliers offer upgraded ceramic hybrid bearings that effectively eliminate this risk.

The AOS separates oil vapors from crankcase gases before they re-enter the intake. When the internal diaphragm fails, oil passes into the intake system causing blue or white smoke on cold starts, increased oil consumption, and oily residue in the intake manifold. More importantly, a failed AOS creates excess crankcase pressure that can push the rear main seal outward, leading to the much more expensive RMS replacement. The AOS part itself costs €100-200, but the repair typically runs €400-800 with labor at a specialist. This is one of the most commonly reported maintenance items on the 987, typically occurring between 80,000-130,000 km. Porsche released an updated AOS design that is more durable than the original.

The rear main seal sits between the engine and gearbox and can develop a leak, especially if the AOS has been failing for an extended period (creating excess crankcase pressure). The seal itself costs under €100, but the repair requires complete gearbox removal, making it labor-intensive. At a European specialist, expect €1,500-2,500 depending on whether other work is done simultaneously. The most cost-effective approach is to combine RMS replacement with a clutch job and IMS bearing upgrade (on 987.1 models), since all three require transmission removal. Many specialists recommend replacing the RMS proactively whenever the gearbox is removed for any reason.

The shift cables that connect the gear lever to the mid-mounted gearbox use plastic ball-end connectors that become brittle and crack over time. Symptoms range from increasingly sloppy gear selection to complete inability to engage one or more gears. This typically occurs between 70,000-120,000 km, with the forum consensus placing the middle of the failure bell curve around 70,000-100,000 km. OEM replacement cables cost €200-300, but many owners upgrade to aftermarket options from Numeric Racing or similar, which offer metal end fittings and come with a lifetime guarantee. Total repair cost with labor runs €500-900. Some owners replace the cables preventively.

The water pump can fail due to bearing wear (causing a distinctive squealing noise) or plastic impeller degradation that spreads debris through the cooling system. Signs of impending failure include dried coolant residue at the pump's weep hole and a squealing sound from the engine bay. Failure typically occurs between 80,000-120,000 km. The pump itself costs €200-400, and labor adds €400-800 at a specialist depending on accessibility. If the impeller breaks apart and sends plastic debris through the cooling system, additional flushing and potential radiator replacement may be needed.

The plastic coolant expansion tank deteriorates from repeated heat cycling over 5-7 years, becoming brittle and developing hairline fractures. These leaks are notoriously difficult to locate because the small amount of seeping coolant often evaporates on hot engine components before it can pool. Symptoms include the coolant level warning appearing every few weeks and a faint sweet smell of antifreeze after parking. The part costs €50-100, but diagnosis and labor add to the total. Many specialists recommend replacing the tank preventively during any major cooling system service. An upgraded tank design is available from aftermarket suppliers.

Cars equipped with Porsche Active Suspension Management (PASM) use electronically controlled dampers that adjust firmness. The internal piston rod seals degrade from heat cycling and constant pressure, eventually causing damping fluid to leak. This is visible as oil misting or droplets on the shock body. Replacement with OEM PASM shocks costs approximately €600-800 per corner including parts and labor. Replacing all four dampers runs €2,500-3,000 at a specialist. Aftermarket alternatives like Bilstein Damptronic offer comparable performance at somewhat lower cost. Non-PASM cars use conventional dampers that are cheaper to replace but still wear out at similar mileages.