2005 Bentley Arnage 6.8L Petrol · N29 PHL

Early iterations of the 6.75-litre twin-turbo L-Series V8 in the Arnage Red Label and Arnage T suffer from premature camshaft lobe wear and hydraulic tappet degradation, particularly between 40,000 and 70,000 miles. Caused by aggressive cam ramp angles combined with early Bosch Motronic ECU calibration and modern low-zinc engine oils. If neglected, flattened cam lobes cause valve timing retardation, rough running, and cylinder misfires. Resolving it requires an engine-out teardown to replace the camshaft, pushrods, and lifters, or retrofitting the post-2007 roller-tappet specification.

On early 6.75-litre Crewe V8 models, cylinder head gasket failure is a documented concern resulting from intense thermal cycling and high cylinder peak pressures inside a tightly packed engine bay. The composite gaskets degrade, allowing combustion gas leakage into the cooling jackets, leading to coolant pressurisation, external coolant weeping, and potential engine overheating. Rectification is labour-intensive due to minimal clearance, requiring the cylinder heads to be skimmed and upgraded multi-layer steel gaskets installed.

With a kerb weight approaching 2.6 tonnes, the double-wishbone suspension and adaptive dampers suffer heavy wear on UK roads. Rubber bushes in the front upper and lower wishbones perish, causing knocks over road irregularities and erratic front tyre wear. In addition, the electronic active dampers and hydraulic accumulator spheres lose damping performance with age, leading to a harsh, jiggly ride rather than the cloud-like compliance intended by Bentley.