The 2017–2020 F150 rattle on cold start Ford confirmed in writing

Start here: your engine and your build date

A rattle on cold start that runs two to five seconds and then clears is the noise Ford documented on the 3.5L EcoBoost. Everything below applies to 2017–2020 F-150s with that engine, built on or before November 30, 2019.

Start with the situation you’re in:

• You just heard it. The next two sections tell you whether what you’re hearing matches what Ford described.
• You’re scared to drive it. Ford put its own position in writing. Section four has it.
• You’re holding a quote. Skip to the parts and hours Ford’s own documents authorize.
• You’re deciding whether to fix it at all. Coverage closed in 2023, which changes the maths.
• Different engine, or a 2020 built later than that? Our Gen 1 and Gen 2 build-date tables sort that out first.

ℹ️ Safety Note: This article covers an engine timing component and the cost of replacing it. It is general information, not a coverage decision or a quote for your truck. Have the noise confirmed by a qualified technician before you authorize a repair that runs to nine and a half hours of labour.

What the phaser rattle sounds like, and what it isn’t

Ford’s program documents describe two distinct noises from a worn cam phaser: a rattle when the engine starts after sitting, and a knock at idle once the engine is warmed up. The cold-start version follows a cold soak of six hours or more and comes from the top front cover area of the engine.

Ford’s dealer documents even include reference sound clips for both noises, which is unusual and tells you how often the wrong noise got diagnosed.

What it is not:

• A noise that keeps going once the engine has been running a minute.
• A 5.0L V8 complaint. The V8’s timing-related noises are separate bulletins with their own build dates.
• Anything the 21B10 software update will silence on a truck whose units are already worn. That update was written to protect phasers, not to quiet ones that have gone.

📋 On the Record: Ford TSB 23-2143, issued 4 May 2023, supersedes 22-2200 and covers 2017–2020 F-150s with the 3.5L EcoBoost built on or before 30 November 2019. It describes a ticking, tapping or rattle noise from the top front cover lasting 2–5 seconds after a cold soak of six hours or more, and attributes it to a worn variable camshaft timing unit. Status checked September 12, 2026: current.

Why it rattles cold and goes quiet warm

A variable camshaft timing unit — the phaser — sits on the end of each camshaft and is positioned by engine oil pressure. Your 3.5L has four of them, two intake and two exhaust.

After the truck sits overnight, oil has drained down and pressure takes a moment to build on startup. A unit with internal wear has play in it until that pressure arrives, and that brief window is what you hear.

🔍 Why It Happens: Oil pressure is what holds a phaser where the computer put it. Cold, with pressure not yet built, a worn unit can move under the camshaft’s own load and knock against its stops. Once pressure comes up it’s held firmly again, which is why the noise vanishes and doesn’t come back until the truck sits.

Ford’s bulletin also lists a second symptom on the same worn units: an intermittent failure to auto-restart during Auto Start-Stop operation, with or without code P164C stored.

Can you keep driving it?

Ford answered this in writing, in the program letter it sent every dealer.

📋 On the Record: In Customer Satisfaction Program 21N03, Supplement #4, dated 25 March 2022, Ford states that a cam phaser which has developed an undesirable noise “does not affect the vehicle safety, performance, or emissions.” The same document scopes the program to 2017–2020 F-150s built at Dearborn from 10 March 2016 and at Kansas City from 15 April 2016, both through 30 November 2019.

That statement covers the noise. It does not cover a warning light, a misfire, or a truck that won’t restart at a stoplight, and none of those are things to drive on while you think about it.

✅ Do This: If a check-engine light is on alongside the rattle, ask the shop to pull and write down every stored code before anything is cleared, and to say specifically whether P164C is present. That record is what tells you whether you’re looking at noise alone or noise plus a driveability fault.

What Ford’s documents actually authorize

This is the part worth taking to a service desk. Ford published exactly which parts and how many hours this job takes, and explicitly told dealers not to go further.

Source: Ford CSP 21N03 Supplement #4 (25 March 2022) and Ford’s current cam phaser bulletin, both filed with NHTSA. Labour times are Ford’s warranty allowances, which are not the same as an independent shop’s book time.

The ML-series numbers matter. They are the later parts Ford moved to, with the earlier HL3Z parts listed only as a fallback when the updated units aren’t available.

Coverage ended, and what that leaves

No Ford program is paying for this repair as of September 12, 2026.

Program 21B10, the software update, ran through 31 July 2022 with no mileage limit. CSP 21N03, the prorated phaser replacement, expired 1 January 2023 and only ever applied to trucks whose 21B10 reflash appeared on a repair order dated 28 February 2022 or earlier. Ford’s separate refund offer for owner-paid repairs closed on that same February date.

Source: Ford’s 21N03 program terms, Supplement #4, filed with NHTSA. Lincoln vehicles used a different table. Shown for context — the program is closed.

Two things are still worth doing. An active Ford Protect contract can cover this repair, and Ford’s own claiming instructions were built to split a bill between the program and Protect. And coverage always transferred with the truck, so a used-truck buyer may find the work already done.

✅ Do This: Ask a dealer to pull your VIN in OASIS and tell you whether 21B10 and 21N03 show as completed. Then check the VIN yourself on NHTSA’s recall lookup, because open safety recalls never expire and are repaired free. Our Recall & VIN Lookup Helper walks through both, and the full F-150 coverage tables list everything Ford is still paying for.

Auditing the quote you’re holding

Start from Ford’s hours, because that number is published and your shop’s is not.

💵 On these numbers: Costs shown are typical ranges, not quotes. Labour rates vary sharply by region and between dealer and independent shops, and parts pricing moves. Use these to judge whether a quote is in the right neighbourhood, not to predict your invoice.

💵 What It Costs: Take Ford’s 9.5-hour allowance and multiply by your shop’s posted rate. At $120 an hour that’s roughly $1,140 in labour; at $180 an hour it’s about $1,710 — before parts, fluids, tax or diagnostic time, and before any related damage found once the front of the engine is open. The hours are Ford’s warranty figure for a non-Raptor F-150, not a retail book time, so an independent using its own labour guide may land higher or lower.

⚠️ Watch Out: The single biggest swing in these quotes is a full timing kit — chains, guides and tensioners — added to the phaser job. Ford’s documents instruct dealers not to replace additional VCT or engine timing components. If a quote includes them, ask what was inspected or measured to justify it, and get that answer on the repair order.

F-150 cold start rattle FAQ

What to do next

Confirm the noise matches Ford’s description, confirm your build date falls on or before November 30, 2019, then take the bulletin number and the 9.5-hour allowance to whoever quotes the job. Coverage is gone, so the only leverage left is knowing exactly what Ford authorized. Every campaign number and date here comes from a Ford bulletin filed with NHTSA, checked September 12, 2026.