I have a 2017 Skoda Octavia TDI estate. Sometimes, after the car has stopped, I hear the engine making a lot of noise. My understanding is that's the fan working to cool the engine down.

Last night, after a 30-minute drive, it started making noise 15 minutes afterwards, and it was very audible from inside the house.

More worryingly, recently the car was parked up for 48 hours, and after 24 hours (of not being driven), I heard the engine making noise for about 10 minutes. Is there any cause for concern?

Edited 27 June, 202527 Jun by boardtc

I would say a cause for concern.

I would want to know why that is happening.

You not say if a TSI or a TDI.

If it did regens because a TDI it should not be a day later.

(updated TDI)
I did not know what regens was but AI tells me...
In diesel engines, "regens" often refers to the regeneration of the Diesel Particulate Filter (DPF).

1. The DPF traps soot particles from the exhaust to reduce emissions, but it needs to be cleaned regularly by burning off the accumulated soot at high temperatures.

2. This cleaning process is called regeneration and can be passive (during long high-speed driving) or active (engine management injects extra fuel to raise exhaust temperature and burn soot).

Edited 27 June, 202527 Jun by boardtc

Regens sometimes begin just before the end of your journey and will continue after you turn off the engine. They can last 10 - 15 mins depending on when, in the cycle, the regen was interrupted.

Unfortunately the ECU isn't smart enough to 2nd guess the distance you've got left to drive when it decides to start a regen.

when you interrupt regen and turn off car, regen stops, fuel in exhaust goes down to dilute oil, and fans are spinning to max speed to cool down DPF, because high temperature without fuel post injection can danage DPF. try not to interrupt renegs, or avoid it as possible, because it dilutes engine oil..

On 27/06/2025 at 15:49, imart143 said:

when you interrupt regen and turn off car, regen stops, fuel in exhaust goes down to dilute oil, and fans are spinning to max speed to cool down DPF, because high temperature without fuel post injection can danage DPF. try not to interrupt renegs, or avoid it as possible, because it dilutes engine oil..

To avoid interrupting the regen, how do you know when to stop your car if a regen is in process?

VAG dpf app if you have android, some cheap obd2 adaper.

i used this one. (9€)

https://www.amazon.com/KVAEY-Car-Auto-Diagnostic-Scanner/dp/B0DKN9VL8Y/ref=sr_1_28?dib=eyJ2IjoiMSJ9.5N2AWbe8pET5wz0alfNdYnJyCOnly6pwgKfedoivlnIkYrAgCvUJb11huYJyo_i75PiUZoQktWj8WqcOIpwH_ZjIHOQSYSl_KsbFk77qXcz_JzV4JdxykCS4ajNMASnp0cHd6UIQQHe31JRi7RgO8uZDroLNaaHs6Rkws_-_ylpf7_pAmaGZhLRTndC3kHLTkFno-KttbFxwxW4mlv--FCPVRXS1UQJJSi0kogrHPDepz81Wk9VGzR7Famiab2PvYSBWio6I3Y5t_Nz3umg_T_RnTEEprkimG_OPj4GX13M.gZnzNl1a9LDQAZKJzlOOvfvu_FpRcPjeOaDSrMdwqKk&dib_tag=se&keywords=bluetooth%2Bobd2%2Badapter&qid=1751364404&sr=8-28&th=1

and google play app (6-7€)

https://play.google.com/store/apps/details?id=com.applagapp.vagdpf&hl=en

9 hours ago, boardtc said:

To avoid interrupting the regen, how do you know when to stop your car if a regen is in process?

One way I have found which is a bit hit and miss is watch the recommended gear, if it's doing a regen it will be recommending a lower gear to increase the exhaust temp

On 01/07/2025 at 19:31, CianKT said:

One way I have found which is a bit hit and miss is watch the recommended gear, if it's doing a regen it will be recommending a lower gear to increase the exhaust temp

Yes and if Its a DSG gearbox it will select a gear lower than expected.

Also the idle RPM will be aprox 1K rpm rather than the usual 850 rpm .

On 01/07/2025 at 19:31, CianKT said:

One way I have found which is a bit hit and miss is watch the recommended gear, if it's doing a regen it will be recommending a lower gear to increase the exhaust temp

Edited 2 July, 20252 Jul by daftbugga
phat fingers