Help? Strange Engine Rumble

[DGraham]

I have recently bought a 2015 model KA which I'm pretty happy with. 

However, recently the engine is making a noise where it sounds like its revving itself but the rev counter doesn't move. The noise lasts only for 15-20 seconds each time and sometimes I hear a louder sound just before it that seems like a valve opening or something like that. It tends to happen when the engine is idling at lights or when at low speed around car parks etc.

I've recorded the noise and uploaded via the link below. The valve type noise is about 15 seconds in then the revving/rumble noise starts

https://whyp.it/tracks/149691/ford-ka-car-noise-1?token=VqERU

I've asked our mechanic to take a look but he's basically said 'unless it happens whilst its in the garage i dont have a clue'. 

Is this a normal engine function? It seems to be getting more frequent.

[KittyKa]

Hi,

I used to have a similar thing on my 2016 KA where it sounds like there is a load on the engine and it rumbles for 10-15 seconds before going back to normal, my lights also used to flicker a little bit when this happens, I believe it could be the alternator charging the battery? Honestly not certain though, I'll report back if I notice mine doing it still.

Hope this is somewhat helpful.

[Oriskany]

Have you got air conditioning? This sounds like the magnetic clutch for the compressor kicking in which drops the engine revs for a while and makes the engine sound like it's under load until the refrigerant starts moving round.

[KittyKa]

Yeah I have air conditioning, does the compressor turn on even when AC is not in use?

[Oriskany]

On 1/21/2024 at 6:50 PM, KittyKa said:

Yeah I have air conditioning, does the compressor turn on even when AC is not in use?

My Ka is a Mk1 with no AC so I don't know, sorry, but perhaps the compressor is occasionally engaged to stir the refrigerant and expel any water build-up. If this effect is in any way predictable you might see the centre of the AC pulley turn as the clutch engages - it should be still when the AC is not engaged. Alternatively, and dependant of access you could either mark the centre of the pulley to see if it moves (with the engine off) or take a picture of its position and then compare this to the pulley later. Good luck.

[DaveT70]

Link doesn't work

[KittyKa]

On 1/16/2024 at 11:23 AM, DGraham said:

I have recently bought a 2015 model KA which I'm pretty happy with. 

However, recently the engine is making a noise where it sounds like its revving itself but the rev counter doesn't move. The noise lasts only for 15-20 seconds each time and sometimes I hear a louder sound just before it that seems like a valve opening or something like that. It tends to happen when the engine is idling at lights or when at low speed around car parks etc.

I've recorded the noise and uploaded via the link below. The valve type noise is about 15 seconds in then the revving/rumble noise starts

https://whyp.it/tracks/149691/ford-ka-car-noise-1?token=VqERU

I've asked our mechanic to take a look but he's basically said 'unless it happens whilst its in the garage i dont have a clue'. 

Is this a normal engine function? It seems to be getting more frequent.

Okay just tried figuring out why my car does this, turns out it's the fan relay, the fans in the Ka turn on and off to keep the engine at 90C. A relay clicks on then the fan runs for 10-15 seconds and then turns off again, doesn't happen when driving at speed but when sat idling it turns on and off occasionally. It's perfectly normal, I hope this helped 🙂

[KittyKa]

This is for the KA MK2 but I'd imagine this happens on most cars tbh

[KittyKa]

Just wanted to come back to this, previously when the fan would click on there would be a rumble, turns out my timing belt has perished and was stretched, replaced it last weekend w the pump etc and now when the fan comes on there isn't really an idle rumble, it just gets a little louder. May be worth taking the top cover off and having a look at it, mine hadn't been changed in 80k miles as I wrongly assumed the previous owner had changed it or gotten it changed 😅

[KittyKa]

On 1/24/2024 at 10:19 PM, KittyKa said:

Okay just tried figuring out why my car does this, turns out it's the fan relay, the fans in the Ka turn on and off to keep the engine at 90C. A relay clicks on then the fan runs for 10-15 seconds and then turns off again, doesn't happen when driving at speed but when sat idling it turns on and off occasionally. It's perfectly normal, I hope this helped 🙂

Also wanted to correct myself, the fans don't turn on when the engine is up to temperature, they turn on when the coolant reaches a threshold temperature.