Ford fiesta rattle/purr noise (video)

brainiack

hi all,

Does anyone have any idea what this noise can be, it’s a Ford fiesta 2016 plate and happens on a cold start (not if already used earlier in the day) rattle/purr noise on starting.

Video link here: https://www.dropbox.com/scl/fi/rk7ps6zb1ysydnadfk2sz/IMG_7524.mov?rlkey=vejrbnjrgqr0awg6k23ew9fc7&st=wjhuzzu6&dl=0

Bigphil1474

I don't know what it is , but it reminds me of the noise the battery makes when it is flat, which it obviously isn't.

Goudy

It sounds to me like one of the electrical relays repeated opening and closing quickly for a few seconds after start up.

Power for things like the starter motor which takes a lot of amps, doesn't pass directly via the ignition to the key/starter button. The key/starter button will produce a small electrical current that opens a relay (electrical switch) and the relay sends the power to that circuit.

It sounds like one of these relays is sticking.

If you have a owners handbook, that might tell you which relay does what as the car will usually have two fuse boxes (one inside and one under the bonnet) stuffed with relays.

You might want to check the ones you know operate on start up like the starter relay.

Get someone to start it up while you listen or feel for the rattling relay.

Something else to listen out for is the starter solenoid, that's an electromagnet on the starter motor that engages it with the starter relay opens. That can often click like that if it's on it's way out, but I expect that to be noisier without the slight delay after starting.

Or on some models of Fords, it's the heater actuators. The small motors on the heater flaps and temperature control can often click and rattle if/when the teeth strip.

Arunmor

The thing I noticed is lack of movement on the rev counter up until the noise stops.

Goudy

https://forums.moneysavingexpert.com/discussion/comment/81898899#Comment_81898899

You might be on to something there.

I wonder if it's due to a low/failing battery. On cold start whatever amps are left in the battery are all being directed to the starter circuit and the ticking is just relays without enough power to actually open them properly until the engine is running and the alternator spinning up.

Try charging or jumping the battery at next cold start, see if that improves things.

Arunmor

https://forums.moneysavingexpert.com/discussion/comment/81899028#Comment_81899028

It sounded a bit like a worn cog on the dial pointer. If it was me I would be leaving it well alone, that will no doubt be a whole new dash cluster. Might give it good rev and see if the needle has a fit.

OP tricky I know but can you narrow down the source of the noise a bit?

brainiack

Thanks guys, I'm hoping its just a battery issue and can be a simple new battery to sort it. Can't find the same on youtube vids etc elsewhere online so it's a mystery.

Going to be selling in a few months but doubt I'd get this noise past potential buyers - will try a battery replacement (hasn't been changed since 2022) so it's about time it was swapped out.

Will report back

Arunmor

A bit of a stab in the dark, good luck with that.

brainiack

Took to garage today and they tested the battery. Its 50% or less and recommended to replace asap to aovid a nasty breakdown or non-start in near future