P000B on Ford

Edge Sport and Edge ST owners with the 2.7L EcoBoost report a distinct 2-3 second metallic rattle on start-up after the vehicle has sat overnight. Oil bleeds out of the variable cam timing phasers while parked; on start-up there is no oil pressure to hold the phaser locking pins, so the phaser internals and the chain tensioners knock until pressure builds. Worn locking pins or their receptacles make the noise progressively longer and louder. Some low-mileage cars have needed chains, guides and phasers outright, with owners in these threads tying early failures to extended intervals and thin bulk oil at dealer services. Unlike the 3.5L Duratec chain stretch issue, this is the boosted 2.7 Nano V6's own phaser/tensioner behavior, and Ford has generally characterized a brief start-up rattle as non-damaging while lengthening rattle indicates real wear.

Separate from the internal water pump, the 3.5L Cyclone's timing drive itself wears. The primary and secondary chain guides and the hydraulic tensioners lose their ability to hold tension when oil pressure bleeds down overnight, so the first two or three seconds after a cold start produce a loud rattle from the front of the engine. Owners report worn tensioner teeth at mileages as low as 56,000, and cases where the noise was ignored until metal debris from a chain sprocket circulated through the oil and forced an engine replacement. Extended oil change intervals and low oil level accelerate the wear because the tensioners are oil-fed. Once cam-to-crank timing drifts far enough, the PCM sets correlation codes and driveability suffers.