2017–2020 Ford F-150 3.5L EcoBoost: Cold-Start Cam Phaser Rattle

Symptom: A loud rattling or “can of marbles” noise from the front of the engine for about 2–5 seconds after a cold start, especially after the truck has sat 2–6+ hours. The noise usually goes away once oil pressure fills the phasers. Day-to-day driving may otherwise feel normal.

Vehicle focus: 2017–2020 F-150 with 3.5L EcoBoost (also reported on related 2018–2020 Expedition / Navigator with the same engine family).

Likely causes (ranked)

1. Worn / failed VCT (cam) phaser locking pins — Consensus cause. Oil drains from the phasers while parked; a failed locking pin lets the rotor slap the housing until oil pressure returns.
2. Inadequate oil pressure at the phasers on startup — Related design/wear issue; Ford and techs describe delayed oil fill as part of the rattle.
3. Earlier “updated” phasers that still fail — Owners who had phasers replaced under older campaigns sometimes got HL3Z-series parts that rattled again tens of thousands of miles later; later ML3Z-series enclosed phasers are widely preferred.
4. Not the same as Gen 1 timing-chain stretch rattle — First-gen EcoBoost (roughly 2011–2016) had more primary-chain issues; Gen 2 (2017+) mainly fights the phaser locking problem.

Rough cost range

Ford’s customer satisfaction / prorated phaser coverage (e.g. CSP 21N03 era) has largely expired for many trucks; confirm any remaining coverage with a dealer using your VIN before paying cash.

DIY or shop?

• Shop job for most owners. Requires valve covers, front cover access, timing care, and often specialty tools.
• Experienced DIY is possible and discussed heavily on EcoBoost forums, but mistakes risk serious engine damage. Not a beginner job.

Useful steps

1. Confirm the noise is short (a few seconds) after a cold soak, from the front cover area — matches Ford’s TSB description.
2. Ask the shop to replace all four VCT units and use the latest phaser part numbers (owners emphasize ML3Z-series over older HL3Z stock).
3. Expect a PCM calibration update as part of Ford’s procedure on applicable trucks.
4. Keep strict oil-change intervals with the correct viscosity; low oil level makes cold-start oil fill worse.
5. Do not ignore a continuous rattle, misfires, or timing codes — that may be a different (more serious) timing issue.

Safety / mechanic note

Ford’s documentation generally treats this as an annoyance that does not by itself affect safety, performance, or emissions. Still have a technician confirm you do not have chain stretch, tensioner failure, or related timing damage — especially if the rattle lasts longer than a few seconds or returns while driving. Verify diagnosis with a Ford tech or trusted indie shop before approving a multi-thousand-dollar repair.