Skoda Superb Engine Fan Running (even when car hasn't been used)

[DreamensioN]

Hi guys,
So my wife's MY18 TDI Skoda Superb has started playing up.

I'm well aware that on all newer TDI engines, if the diesel particular filter was in the middle of doing a re-generation, that when you turn the engine off it's common for the engine fan to run at full speed for several minutes.

This is just like that - but it's not several minutes. It's 20-30min, up to 1hr. Since she started working from home, she has been doing much shorter drives. Previously she would drive the car for 30-45min twice a day (to/from work), and also go down to the Gold Coast (1hr+) twice a week. These were nice long drives where the DPF could regenerate while driving. Only occasionally would she return home, turn the engine off, and the fan would continue running for a few minutes.

Since March (and the lock down here in QLD), she has been working from home - so most drives are now 15-20min within our local area. She has done a couple of long drives (1hr+), but these are few and far between - maybe once a fortnight etc.

The last 6 months we've noticed the engine fan running a lot more when she returns home. We thought this was normal, but also started to notice that it was running for A LOT longer. About 2 weeks ago, it ran for so long it flattened the battery and because she was away from home - she had to call road side assistance to get a new battery. I also noticed that the fan will run, and if we open the drivers door, it will stop, but then restart again in about 30 seconds. And it will constantly do this for several cycles of about 5 minutes at a time.

And the reason why I'm posting this now is because yesterday (Sunday) she didn't even drive the car all day. And yesterday afternoon we heard this noise coming from the garage, and yep...the fan was on full speed.

Anybody know what would be trigging this, or what I could possibly look at/look for if I hook up the VCDS software? Like I said - I get that it's normal after the car has just been turned off...but I don't think it's normal for it to run for SOOOOO long, and then also for it to just randomly turn on when the car hasn't even been used for 24hrs+. The concern here is that she'll be stuck in middle of nowhere again with another flat battery waiting for roadside assistance.

[Lucas_R]

Was the car locked in the garage when the fans were running yesterday? Or was the car unlocked? If left unlocked, then the car is still "alive" so although odd, I can semi-understand that the fans may turn on. Very odd that it would allow the battery to run flat though.

It definitely sounds like the car is desperately trying to do a DPF regeneration. If your current driving is only 15-20mins then the car would not get up to temperature for the DPF regen to run its cycle, hence the fans running when you turn the engine off. In my experience with my SQ5 TDI, the regen will not initiate until the oil temp reaches 80 degrees and this takes a good 15 mins of driving for the oil to get to this temp. The actual regen process takes a good 15-20 mins so with that in mind, you need to take the car for a good 40-60 min drive to let it get up to temp and allow the DPF regeneration process to carry out its task in full.

I would also heavily suggest you invest about $50 into a Carista dongle and the VAGDPF app so you can monitor your cars DPF levels and regeneration process: VAG DPF app on Android to monitor DPF

[Lucas_R]

Any update? Not sure what covid restrictions you might have in QLD, but if you can, I would suggest taking the car for a good spin on the freeway for at least 40 mins. Once the DPF regen starts, you can potter around town if you want and it will continue to clean, but the best way to get it started is a 80kph or more drive on the freeway once the oil etc is all up to temp.

[ope126]

I can't offer any advice on your TDI, except if it is still under warranty, take it back to the dealer for a check.

The kms you do are no different to my Passat (same engine) and it does not have the same symptoms.
Yes the fans run, but not to the extent of yours.

These guys are located at Beenleigh and might be worth a try; Diesel Particulate Filter | DPF Cleaning Brisbane | DPF Replacement Brisbane

Let us know how you go!

[DreamensioN]

Thanks guys.
I got the wife to take it for a 1.5hr drive yesterday, so we're keeping an eye on it. Also last night I took the car for a drive but once the engin heated up, I kept it up in the rev range (for a diesel) at 2500-3000rpm in manual mode. I'm hoping that this was enough load on the engine to generate the heat to trigger a regen and burn out whatever it thinks is in there.

We're keeping an eye on it and will see how it goes. I also found on the Ross Tech website how to trigger an "emergency DPF regen" via VCDS. So if this happens again in the near future, I'll do that.

Yep the car is still well within the warranty period. It's only 2.5yrs old (with a 5yr warranty). My wife did mention it at the last service she recently had (about 3 weeks ago), but they said the fan running is normal. I think they may have misunderstood - as we get it's normal...but not normal to run for extended periods, or when the car hasn't even been used.

Out of interest - do any of you know how often the DPF will regenerate? Is it something that only happens once in a while (or takes a while to build up before a regen is triggered?), or is it actually something that can happen everytime the car is driven if conditions are right?

[Lucas_R]

Out of interest - do any of you know how often the DPF will regenerate? Is it something that only happens once in a while (or takes a while to build up before a regen is triggered?), or is it actually something that can happen everytime the car is driven if conditions are right?

Different engines will need to regenerate at different times, but as a rough guide, my SQ5 with the V6 TDI needs to do a regen every 450-500km or so with our type of driving, but if driven solely on the motorway the soot accumulation is much slower, so it would be every 700-800km or so. With urban driving and constantly being on and off the throttle, the soot accumulates much more quickly.

For a very small outlay, the VAGDPF app and Carista dongle as mentioned in my previous post would be a valuable tool and will pay for itself in no time. Much more convenient than VCDS and the information is displayed in a way that makes it basically foolproof to misunderstand.

Ahh, almost forgot - so if the car has exceeded 100% in terms of DPF soot level, and has tried on several occasions to do a regen but has been interrupted (eg engine turned off) then it will go into a soft limp mode (may or may not show a light on your dash at this stage) but basically it will cease even trying to initiate a regen. This will require a manual regen triggered with VCDS or Carista. But if the soft limp has gone on for too long, it may require a trip to the mechanic to have the DPF cleaned manually (either with chemicals sprayed into it or removal of the DPF and cleaning with high pressure water).

In my case, the soft limp mode went on for too long, mechanic could not trigger a manual regen, resulting in a full on limp mode shortly after with absolutely no power (seriously dangerously slow - absolutely absurd how slow the car was) and I had to physically remove the DPF and flush them out with high pressure water, before using VCDS to reset all of the DPF parameters (basically telling the car that a new DPF has been fitted).

[ope126]

Similar to Lucas_R, the Passat does a regen every 400-500kms. And you know it is taking place.
I have owned a couple of MD Mondeo Titanium's in the past and they use a "High Flow" DPF and basically, I never really could tell when the regen took place. It was that efficient.
Here is a guy at Browns Plains who can doe on car DPF cleans also; On-car DPF Cleaning - Steve Sorensen Mechanical

[JustCruisn]

Hey DreamensioN I thought your handle looked familiar, I remember having your 'Bedroom Sessions 7' on high rotation many many years ago. I feel old now.

[DreamensioN]

Thanks for the tips guys - and I've placed an order for that dongle. Cheers!

Hey DreamensioN I thought your handle looked familiar, I remember having your 'Bedroom Sessions 7' on high rotation many many years ago. I feel old now.

Haha yep - that's me! Wow... BS7 was such a long time ago! I had my own podcast for about 10yrs on AH.FM - Leading Trance Radio, but I've since given that up just due to life getting in the way. I still dabble now and then with it though but nothing consistent or serious quite a while.

[DreamensioN]

Hey guys - just looping back to this.

The car kept doing it and most recently we finished a 5hr drive (Harvey Bay -> near Beaudesert) and after finishing that trip the fan kept running non-stop for 1hr and 20min. That's when the battery started running out of power. We filmed the whole thing and took photos, and the battery eventually went flat.

While this was happening, doing things like opening the drivers side door, locking/unlocking the car would cause the fan to stop for about 20 seconds, then it would just start up again.

The car ended up on the back of a tow truck to Skoda, and it turns out there was a faulty fan relay. It couldn't turn off.

So the car is now fixed and hopefully that's the end of that.