I have a 2013 F-150 with 77k miles and the 5.0L engine. A few months ago, I started hearing an odd rattle during startup. I checked the heat shield clamp and it seems to be intact and tight. Ended up taking my truck to the dealership to have an oil leak repaired and they were not able to replicate the rattle (although I hear it at every single cold start and sometimes when warm).

Just last week, I had my truck back at the dealership reworking all of the IWE and asked for them to check out the "rattle" again. They were finally able to replicate it and diagnosed it as "chain slap." They said it could be related to any one of the timing components. Long story short, they replaced all the phasers, timing chains, tensioners, sprockets, guides, etc. and after all that work the "rattle" is still there! Completely unchanged.

I have attached a few videos below. The first video is a cold start where you hear the rattle a few seconds after startup, it stops for a few seconds and then rattles again (it almost sounds like it pauses when the A/C compressor engages?). This occurs at every single cold start. The second video is when the engine is warm and it rattles very briefly at initial startup.

Any ideas? I have been pulling my hair out. Any help would be greatly appreciated.

 

Maybe have someone watch the tensioner pulley, see if that’s jumping around at all. Also try a cold start with you foot on the gas so it cranks only and doesn’t start, see if the sound is still there.

 

Tensioner pulley looks fine - not moving around and doesn't seem to be creating the noise.
Held down the gas pedal and started for about 10 seconds - no "rattle" present during dry start. Immediately started the engine afterwards and the "rattle" was still there/unchanged.

 

Only other thing I can think is maybe take the belts off and spin water pump by hand, I’ve had those make a funny startup rattle, wish I could help more.

 

Ford dealership is thinking it is the starter. They said the gears might be worn out and it is trying to reengage post start.

I am not sure that I am convinced. It seems like it wouldn’t make a difference if it was a cold start or warm start if the problem is the starter itself (rattle is consistently much worse on cold start). Thoughts?

I’ve attached another video for reference.