Timing Chain Tensioner Failure and Camshaft Rattle (2.5 & 2.7 V6)
SeriousEngineThe 2.5-litre (H25A) and 2.7-litre (H27A) all-aluminium 24-valve V6 engines utilize a complex multi-chain timing system with hydraulic tensioners and plastic-lined guides. Infrequent oil changes or using incorrect oil viscosity causes carbon sludge to restrict oil supply ports to the hydraulic chain tensioners. This leads to collapsed tensioners, severe chain slap against the timing cover on cold starts, guide disintegration, and potential catastrophic valve-to-piston contact if the chain jumps timing teeth.
Loud metallic chattering or rattling noise from the front of the engine for several seconds after a cold start, Persistent rhythmic ticking or buzzing sound that increases in pitch with engine revs, Check engine light illuminated due to camshaft/crankshaft timing position correlation codes
- Start the engine from completely stone cold and listen closely near the front aluminium timing covers
- Inspect the engine oil filler cap and valvetrain through the hole for thick black sludging
- Review service invoices to confirm timing chains and hydraulic tensioners have been renewed