Primary and Secondary Timing Chain Tensioner Cracking
SeriousEngineEarly AJ-V8 engines fitted to the X308 were assembled with plastic-bodied primary and secondary timing chain tensioners. Over years of thermal stress and exposure to combustion byproducts, the plastic casing becomes brittle and fractures. When the plastic guide shoe delaminates, the secondary chain slips on the camshaft sprocket, throwing valve timing out of synchronization and causing the valves to strike the pistons, typically requiring a complete cylinder head rebuild or replacement engine.
Prominent metallic ticking or rattling from the front timing cover during the first five seconds of a cold start, Rough idle with misfire fault codes stored for banks 1 and 2, Sudden total engine failure with rapid cranking speed and zero compression
- Inspect service records for specialist invoices detailing third-generation metal-bodied tensioner replacement
- Ask the seller if the cam covers have been removed to inspect the colour of the upper tensioners (metal body is silver, plastic is orange/brown)
- Listen carefully for mechanical slap around the front of the cylinder heads during a dead-cold startup