Rotational rattle noise.

[Intuit]

It’s never “great” to hold the clutch pedal in on any manual car because it loads up the crankshaft thrust bearing. Ironically, it’s less stressful on the thrust bearing to hold the RPM up (as in two-step/launch) - higher shaft speed = stronger oil film on any fluid film bearing.

Yes this is actually in the owner's manual for our vehicles. Not the case with the prior vehicle and motorcycles.

I suspect the additional heat from holding the RPMs higher would contribute to a higher failure rate. Never had to touch the slave with the first vehicle but it was on the outside of the bell housing. (where it should be for a daily driven passenger vehicle)

 

[Yelbom15]

And just so I understand. When I release clutch, RPMs rise to normal idle. When pressing, RPMs drop ever so slightly. I assume that’s the computer getting ready for you to shift? If I understand correctly, brake system and the slave cylinder use no power from the engine. It’s just a hydraulic system. I know it varies from vehicle but I also feel a “pulsation” when in first.
I’m coming from a MK6 TDI that also had some quirky things. Just want to learn the normal side of these Fiestas.

 

[Intuit]

As I cruise and I see a green light turn to a red light, I press on the clutch, shift into neutral and let it coast to a stop with my foot down on the clutch. That is when I hear the chatter. Once I stop even with the clutch still pressed, the chatter disappears.
Shifting and holding a gear is smooth as butter but the noise always had me curious due to everything else being perfect.

I don't believe this is the same thing that I was referring to then.

And just so I understand. When I release clutch, RPMs rise to normal idle. When pressing, RPMs drop ever so slightly. I assume that’s the computer getting ready for you to shift? If I understand correctly, brake system and the slave cylinder use no power from the engine. It’s just a hydraulic system. I know it varies from vehicle but I also feel a “pulsation” when in first.
I’m coming from a MK6 TDI that also had some quirky things. Just want to learn the normal side of these Fiestas.

Sitting still at idle, the RPMs are not notably affected by depressing/releasing the clutch pedal with mine; whether in neutral or first gear. It could be the throw-out bearing that @Dialcaliper mentioned or/and the clutch dragging. If the "pulsation" only occurs with your foot on the pedal in first gear, it may be dragging. Since there's no adjustment (that I'm aware of) may try power bleeding the hydraulic system. My prior vehicle had a hydraulic system for the clutch pedal, but there was an adjust at the clutch pedal.

 

[Yelbom15]

@Intuit thank you. I’ll look into bleeding the system. It’s very intermittent. I’m sure if I took it to the dealer, it wouldn’t make the noise with my luck.