1998 Daimler Super V8 4.0L Petrol · N20 JAG

Early 4.0-litre AJ-V8 engines (AJ26S and AJ27S) in the X308 Daimler Super V8 were fitted from the factory with plastic-bodied secondary camshaft timing chain tensioners. Over time, engine oil heat cycles and mechanical fatigue embrittle the nylon plastic bodies and slipper shoes. The plastic body cracks or breaks away completely, allowing the timing chain to slacken and jump sprocket teeth on startup. In the worst cases, the camshaft skips multiple teeth, causing the valves to strike the pistons and destroying the cylinder head. Upgrading to robust metal-bodied third-generation tensioners with shorter bolts is an essential preventative modification.

Prior to late 2000, 4.0-litre AJ-V8 blocks used a nickel-silicon carbide (Nikasil) electro-plated bore coating in place of traditional cast-iron cylinder liners. High sulphur concentrations in 1990s UK petrol reacted with combustion moisture to form acidic compounds that chemically eroded the Nikasil coating. Pitted cylinder walls caused piston ring blow-by and loss of cylinder compression, resulting in difficult cold starting or total refusal to fire after short start-and-stop moves ('bore wash'). While modern low-sulphur fuels halted active erosion, surviving original Nikasil engines must be checked for stable compression and blow-by before purchase.

Both the X308 and X350 generations of the Daimler Super V8 utilise an independent rear suspension layout featuring multi-link arms, aluminium wishbones, and rubber-metal bushes. The immense torque (up to 400 lb-ft) of the supercharged powertrain combined with UK potholes and speed bumps places enormous stress on the lower wishbone bushes and hub carrier ball joints. The rubber perishes and develops excessive play, allowing the rear wheels to steer passively under acceleration and braking. In addition to creating an unsettling floaty sensation on motorways, worn bushes result in MOT failure and rapid inner tyre shoulder scrubbing.