At its debut, the 996 featured the most significant change from the classic 911 series: a water-cooled engine replacing the previously air-cooled engine. Progressively stringent emissions and noise regulations, environmental concerns, a higher expectation for refinement and the need for a high-performance 4 valve per cylinder engine made the switch necessary.
Most models of the 996 generation of the Porsche 911 (excluding GT3 / GT3 RS / GT2 & Turbo models) sports car were afflicted with a vulnerability in the intermediate shaft (IMS) that drove their engines’ camshafts. Failure of the ball bearing within the IMS leads to varying degrees of engine failure. In general, after an IMS bearing failure, the engine internals could be contaminated with debris from the failure that requires the engine to be stripped and rebuilt. In severe failure modes, cam timing could be affected, leading to valve-piston impact, necessitating a rebuild or replacement of the entire engine.
In 2000, Porsche introduced the 996 Turbo, equipped with a four-wheel-drive system and a 3.6-litre, twin-turbocharged and intercooled flat-six engine generating a maximum power output of 309 kW (420 PS; 414 hp). In 2002, the standard Carrera models underwent the above-mentioned facelift. In addition, engine capacity was also increased to 3.6-litres across the range, yielding gains of 11 kW (15 PS; 15 hp) for the naturally aspirated models.