Fan still running after engine off

[Fpm]

Just bought a four year old octavia estate 1.6 . Sometimes fan stays running for a while after engine is turned off 

[Ootohere]

Welcome to the forum.

Maybe it needs to run for a short time and only a short time if there is a regen happening & if this is a 1.6 TDI CR.

 

Is the coolant level correct and the Anti Freeze / Summer Coolant / Corrosion Inhibitor strength correct.  ie the Antifreeze.

[VRS_White_Hatch]

It used to be the case that when the turbo was still spinning the fan stayed on. If your drive is on boost until shortly before you stop its likely a turbo spinning at 100,000 rpm will still be spinning when you stop. It's just something I heard or read - maybe someone can confirm or correct me?

[MarkyG82]

More likely to be a the dpf doing a regen.  I can't remember whether it's still doing the regen when it happens or if it's been interrupted and needs to go again next startup.  If needs to go again it wont do it till you are up to speed/heat.

[lway]

 

Big Sticky at top of the forum

[Fpm]

Sorry what is a regen . I read that if the fan runs like this to long or often it can damage the fan also that it could be something like a relay replacement 

[daftbugga]

sounds to me like a regen that has been interrupted.

regen is a regeneration on the  DPF ( Diesel Particle Filter ) long story short is the particulates ( soot  ) is burnt & turned to ash , the filter needs to get vey hot for that to happen.

 

 

https://www.rac.co.uk/drive/advice/emissions/diesel-particulate-filters/

Also have a look @ the thread that Iway  has shown.

Edited 12 October, 2020 by daftbugga
Added a link

[Fpm]

I’ve not had a warning light come on . It doesn’t stay on all time , I’ve only noticed this a few times mainly because my last car never did this . 
I went out yesterday drove for just over an hour parked up stopped engine no fan yet when I drove home again just over an hour I parked up and fan ran for at least 5 mins after I shut engine off 

[varaderoguy]

54 minutes ago, Fpm said:

Sorry what is a regen . I read that if the fan runs like this to long or often it can damage the fan also that it could be something like a relay replacement 

 

A Regen or Regeneration process - is the process whereby the car burns off the excess carbon build up in the DPF (Diesel Particulate Filter).  This is done by usually injecting some extra diesel into the DPF and a controlled burn happens which cleans out the DPF.  It is recommended that at least once a week, that a longer journey takes place - and that you push the car a bit faster and harder (some folks like to call it the Italian Tune-up method).

 

In therory, keep the engine speed at around 2000rpm over a period of miles (maybe drop a gear) - will help the car to achieve the cleaning process.  The fan kicks in to help promote the burning cycle.

[daftbugga]

25 minutes ago, Fpm said:

I’ve not had a warning light come on . 

 

You don't get a warning light come on until the DPF is very clogged, it's  then time  for an Italian tune up , ignore that & the car is likely to go into limp mode.

you can drive like miss daisy for 1 hour & the filter wont get hot enough .

[MarkyG82]

@Fpm what does your driving pattern look like?  Is it mainly town driving or motorway? Do you drive with economy in mind or push a bit harder?  This will give us an idea of the condition of the DPF.  A 4 year old 1.6tdi driven around town for its life will almost certainly be in need of a long run at higher than normal revs.

[J.R.]

If the fan remains on after you shut down then (if you have the time) take it for a drive above 2.5k rpm for 10-15minutes to allow the regen to complete its work.

 

I would rather do that and get the benefit of the fuel wasted starting the reaction than to lose it and have the fans running to cool down a smoking hot DPF.

[daftbugga]

One thing I forgot to mention is RPM @ tickover , when a regen is happening  you will find that the revs @ idle  are 1000 rather than the usual 850-900 it will feel almost as though the throttle has partially stuck open.

[Fpm]

Tbf 7 miles ether way to work through the week . Long drive out once or twice a month . 
just seems strange it was fine I my drive out was parked for 2-3 hours before hour drive back . 
so if you drive long enough for the regen to complete the fan should not come on when engine is turned off . 
My last car was diesel and never experienced this fan situation with that car 

[durhamfisher]

Unless you get a warning light just ignore the fan, is working as designed. Yes, if a regen starts and you drive far enough for the regen to complete the fan will not be on when you park up. Another indication of a regen in operation is 1k revs at tick over and stop start not operating when parked.

Edited 12 October, 2020 by durhamfisher

[paulski]

2 minutes ago, durhamfisher said:

Unless you get a warning light just ignore the fan, is working as designed. Yes, if a regen starts and you drive far enough for the regen to complete the fan will not be on when you park up. Another indication of a regen in operation is 1k revs at tick over and stop start not operating when parked.

 

Totally agree with above. So to sum up for you. 

 

1. Fan stays on and if you get out the car there will be a acrid burning smell accompanying this. 

2. At idle the revs increase to 1000rpm when the car needs to actively carry out this. Start stop will not function until the regeneration has completed. 

3. It's totally normal for this to happen. 

4. You can turn the engine off during a regeneration process. It won't do any damage. 

5.  you will get a warning light if the DPF is too clogged. If you get this then don't ignore it else it could be costly. 

 

 Hope that helps. 

 

 

[Fpm]

So I’ve only had the car a few weeks and the fan has come on a few times now should it be this frequent

[daftbugga]

1 hour ago, Fpm said:

So I’ve only had the car a few weeks and the fan has come on a few times now should it be this frequent

 

it all depends on the sort of journey you are doing, lots of shortish trips with not many revs on that will happen .. if you routinely do trips of 10 or more miles most of it done with engine revving @ 1500  -  2000 or more rpm it may never happen .

like I said earlier you can drive like miss daisy for 1 hour & the filter wont get hot enough, you need to remember the higher the rpm the hotter the exhaust gases.

[Fpm]

Thank you for all your help it’s put my mind at ease . 😀