2019 W205 Radiator Fan runs at high speed after a journey as soon as the ignition is turned off

[RobWales]

I recently bought a petrol 2019 C Class Mercedes C200 AMG W205 saloon, 32k miles (1.5 turbo engine)
It runs well, but after any journey, even only a couple of miles, as soon as I switch the ignition off the radiator fan kicks off at high speed, and continues running for approx 6-7 mins before turning itself off.
Called in to my local indy Mercedes garage earlier this afternoon, and they popped their diagnostic tool on it, but found no error codes, so said to "keep an eye on it"
Should I be concerned about this, or just accept it and hope over time it doesn't knacker the battery?
Cheers, Rob

 

[BfgSLKMan]

Well if it was a diesel then I would say it was doing a particle filter regen when you swtiched it off. Some petrols to have them too - and yours is one of them: Mercedes-Benz M260/M264 engine - Wikipedia
Hard to believe that the MB Garage couldn't work that out?

 

[alexanderfoti]

Ac pressure sensor is a favorite for causing this

 

[RobWales]

Ac pressure sensor is a favorite for causing this

Thank you for this comment, I suspect you may be right - but wouldn't this show an error code on their diagnostic?
Tia, Rob

 

[alexanderfoti]

No, it if in range. If the car things the ac pressure is maxed out, it won't be a fault if its hot outside.

 

[optimusprime]

Make sure about this , on some cars its to cool down the engine and interior after a long run .

 

[alexanderfoti]

Make sure about this , on some cars its to cool down the engine and interior after a long run .

Possible but op says:

I recently bought a petrol 2019 C Class Mercedes C200 AMG W205 saloon, 32k miles (1.5 turbo engine)
It runs well, but after any journey, even only a couple of miles.

It has to be roasting hot for it to do this.

 

[RobWales]

Many thanks you guys for your advice.

Having had the fan blast away for 6 mins again this cool autumn morning after a local 3 mile journey, I bit the bullet and phoned my local MB Main Dealer service dept, where I received prompt, enlightening and helpful advice from their service manager .ie
- this is definitely not normal fan behaviour - something is amiss. (aha, progress)
- on checking his computer he was pleased to advise my model has the latest software that transmits engine info direct to their MB computer, and on look up he could see the 2 error codes that were generated earlier this morning (wow, I didn't know this was possible)
- the 2 error codes were Radiator Flap, and DPF Regen (as mentioned above yes a petrol car, but one of the earliest models to have DPF)
- plus a software update is required (which they will do after pinning down the true causes of the error codes)

So full marks to the local Main Dealer, who will do a full diagnostic check and cost of repair report late next week (for £99 which I hope to recover eventually from the warranty claim)

Will make a final posting to conclude this thread when the work has been completed.

 

[RobWales]

Well here we go, my update following the local Mercedes dealerships diagnosis (Cost £99) earlier today.

Firstly, they tested the radiator flap function and found no issue there. Then they tested and found the Petrol Particulate Filter (PPF , or GPF for the Gasoline acronym ) regen to be working ok. So no remedial work required.

So, me being rather unsatisfied with this explanation, and having spent £99 for another negative outcome diagnostic, I asked to speak with their maintenance manager for a fuller explanation....

He was very pleasant and we had an interesting 15 min discussion, where my constant probing as why should this 3 year old 32k mile Mercedes have a 6 minute fan overun everytime I turn the ignition off ... and this was the eventual advice......

....because I only use the car for short local journeys of typically 2-3 miles, "the PPF is constantly trying to do a PPF regen to burn off accumulated soot particles. But because it doesn't get hot enough to finish its cycle it will over-run the fan for upto 6 Mins after the ignition is turned off."

So, I asked, have I bought the wrong spec Mercedes as I only ever do short journeys theses day being retired, and usually take my other car a 20 year old Z4 away for longer trips. To which this was his advice...."yes unless you take it out for a long run regularly this is the wrong car for you"

To which I replied that having just spent £22k buying this car I am reluctant to trade it in anytime soon, so how should I keep the PPF regen working properly meanwhile, to which I was advised "you should plan to take it on the motorway for a 40-50 mile run about once a fortnight, and don't just cruise but keep the revs high"

Dumbfounded, I paid my bill, and left the dealership.

If his advice is right, Mercedes are knowingly marketing and selling new petrol cars that have PPF systems fitted, in the knowledge that they are not suitable for buyers/drivers who do not regularly do long motorway type journeys? Surely not!

 

[RobWales]

Well here we go, my update following the local Mercedes dealerships diagnosis (Cost £99) earlier today.

Firstly, they tested the radiator flap function and found no issue there. Then they tested and found the Petrol Particulate Filter (PPF , or GPF for the Gasoline acronym ) regen to be working ok. So no remedial work required.

So, me being rather unsatisfied with this explanation, and having spent £99 for another negative outcome diagnostic, I asked to speak with their maintenance manager for a fuller explanation....

He was very pleasant and we had an interesting 15 min discussion, where my constant probing as why should this 3 year old 32k mile Mercedes have a 6 minute fan overun everytime I turn the ignition off ... and this was the eventual advice......

....because I only use the car for short local journeys of typically 2-3 miles, "the PPF is constantly trying to do a PPF regen to burn off accumulated soot particles. But because it doesn't get hot enough to finish its cycle it will over-run the fan for upto 6 Mins after the ignition is turned off."

So, I asked, have I bought the wrong spec Mercedes as I only ever do short journeys theses day being retired, and usually take my other car a 20 year old Z4 away for longer trips. To which this was his advice...."yes unless you take it out for a long run regularly this is the wrong car for you"

To which I replied that having just spent £22k buying this car I am reluctant to trade it in anytime soon, so how should I keep the PPF regen working properly meanwhile, to which I was advised "you should plan to take it on the motorway for a 40-50 mile run about once a fortnight, and don't just cruise but keep the revs high"

Dumbfounded, I paid my bill, and left the dealership.

If his advice is right, Mercedes are knowingly marketing and selling new petrol cars that have PPF systems fitted, in the knowledge that they are not suitable for buyers/drivers who do not regularly do long motorway type journeys? Surely not!

Addendum: after a subsequent 26 mile motorway "blast", turned off the ignition, and guess what, immediately there was 6.5 mins of a high radiator fan blast. Not sure what to do next.

 

[alexanderfoti]

I think worth a second opinion. I don't think they have any evidence of it actualyl doing a regen, and are just assuming its that.

 

[Bayleaf]

Only just come across this thread so apologies for being late. But this is the first time I have ever heard of a petrol engine having a particulate filter.

 

[FiveAlive]

Well, nowadays they sometimes do thanks to ever-stricter emissions regulations. The petrol ones don't tend to have the same issues as diesel ones because the exhaust can be brought up to burn-off temperature more easily. But, as the OP discovered, only ever doing 2-3 mile journeys clearly isn't quite enough for them. Speaking of whom, the OP would probably be best off with an EV - no worries about premature wear due to never getting the engine warmed up.

 

[RobWales]

Well, nowadays they sometimes do thanks to ever-stricter emissions regulations. The petrol ones don't tend to have the same issues as diesel ones because the exhaust can be brought up to burn-off temperature more easily. But, as the OP discovered, only ever doing 2-3 mile journeys clearly isn't quite enough for them. Speaking of whom, the OP would probably be best off with an EV - no worries about premature wear due to never getting the engine warmed up.

I have been driving the car daily for over 3 months now, invariably on journey of 3-5 miles. I have found that the previous Dealership advice above to be correct ie after about 4-5 weeks of my short journeys the fan starts overunning again, and to correct this I take it out for a 30 mile high rev blast on my local motorway, which resolves the issue.
Its a great car otherwise so I am not at all tempted to go EV yet, but it something to be aware of.

 

[Riverman]

I have been driving the car daily for over 3 months now, invariably on journey of 3-5 miles. I have found that the previous Dealership advice above to be correct ie after about 4-5 weeks of my short journeys the fan starts overunning again, and to correct this I take it out for a 30 mile high rev blast on my local motorway, which resolves the issue.
Its a great car otherwise so I am not at all tempted to go EV yet, but it something to be aware of.

Hi Rob
Very interested to read your report on fan shutdown delays
I purchased a new c43 AMG Coupe in June 2023. Like you most of my journeys are now local. I never experienced the 'running fan' problem until about 3 or 4 months ago. I used to drive about 12,000 miles per year but since retiring, buying this new car and moving home my mileage last year was only 2000. The car has just started showing the same symptoms you describe. After parking and turning the car off the engine fan runs at high speed for about six minutes. I don't quite understand why the fan should be running at high speed after parking following a short journey. If the PPF if not getting hot enough during short journeys to regenerate why does the engine need extra cooling from the fan after shutdown?

I assume the fan takes a fair amount of power judging by the fuse rating and because of the short journeys I suspect the battery may not be recharged enough during these short runs. When I leave the car garaged during holidays I connect a C-TEC charger to keep the car battery topped up.
I am now tempted to connect the charger after every journey if this is deemed a 'normal' car shutdown procedure.

I love this great car after exchanging my Jaguar XKR 5 litre supercharged for this 4 x 4 box of electronics but there seems to be a lot to learn about how it all works. I also love these forums and appreciate the knowledge and experiences of other owners

 

[Supernoodle]

I don't know much about the C43, but what you you describe sounds like fans are being requested in after run (time after key off). I'm guessing from your description this isn't normal and doesn't coincide with some update or other event?

Normally in the ECU software multiple features (oil, exhaust, fuel, AC, etc) can request cooling during the after run. It works on a max wins basis. There will so be a max time the ECU can be in after run before it shuts down ( possibly why it's always 6 mins for you). It's quite possible that some feature is receiving some dodgy temp that makes it think it needs the additional cooling. First check for errors, if none check all the temps possible on a diag tool, preferably Xentry to see if they are plausible. Stuck in range sensors may not generate a fault.

 

[recycled]

Well here we go, my update following the local Mercedes dealerships diagnosis (Cost £99) earlier today.

Firstly, they tested the radiator flap function and found no issue there. Then they tested and found the Petrol Particulate Filter (PPF , or GPF for the Gasoline acronym ) regen to be working ok. So no remedial work required.

So, me being rather unsatisfied with this explanation, and having spent £99 for another negative outcome diagnostic, I asked to speak with their maintenance manager for a fuller explanation....

He was very pleasant and we had an interesting 15 min discussion, where my constant probing as why should this 3 year old 32k mile Mercedes have a 6 minute fan overun everytime I turn the ignition off ... and this was the eventual advice......

....because I only use the car for short local journeys of typically 2-3 miles, "the PPF is constantly trying to do a PPF regen to burn off accumulated soot particles. But because it doesn't get hot enough to finish its cycle it will over-run the fan for upto 6 Mins after the ignition is turned off."

So, I asked, have I bought the wrong spec Mercedes as I only ever do short journeys theses day being retired, and usually take my other car a 20 year old Z4 away for longer trips. To which this was his advice...."yes unless you take it out for a long run regularly this is the wrong car for you"

To which I replied that having just spent £22k buying this car I am reluctant to trade it in anytime soon, so how should I keep the PPF regen working properly meanwhile, to which I was advised "you should plan to take it on the motorway for a 40-50 mile run about once a fortnight, and don't just cruise but keep the revs high"

Dumbfounded, I paid my bill, and left the dealership.

If his advice is right, Mercedes are knowingly marketing and selling new petrol cars that have PPF systems fitted, in the knowledge that they are not suitable for buyers/drivers who do not regularly do long motorway type journeys? Surely not!

so if it doesnt get hot enough it over runs the fan? What is the fan doing? cooling dow nthe car that is not hot enough?

 

[Riverman]

so if it doesnt get hot enough it over runs the fan? What is the fan doing? cooling dow nthe car that is not hot enough?

This original post has gathered some interesting comments. I have the same problem and can definitely say that the advice given by the dealer’s service manager is correct

Short journeys do not let the regeneration of the PPF complete. After I take a longer drives the ‘problem’ goes away and the fan does not stay on at the end of the long drive. Like the other responders I cannot understand how the software logic keeps the fan running if a regeneration is not completed. But I am not the software coder who considered the implications of not completing the PPF regeneration

But I am now satisfied that my car seems to be working as designed and that is the end of the matter

 

[HITECH]

A regen ONLY starts according to all the parameters being correct. Yes a petrol engine will get up to temp quicker. It is NOT NORMAL for any petrol or diesel car to constantly regen UNLESS the content goes high enough to kick in OR the pressure sensor is faulty. My guess is the cars doing it have been software updated with newer emmisions (lower) tolerances. Also a Mercedes will not regen if there are any DTC codes in the ECU.
I work on all types of german cars and find this is common more so with VW's since the recall to give them all software updates after the vw emmision crap stuff.
So mercedes have to follow the band wagon. update software and when they update it and lower the emmision tolerances what the manufacturers HAVE NOT DONE is replace the pressure sensors aswell as they are spec'd to go hand in hand with software from date of manufacture.
All the cars with this on running fan after engine off had got software updates within the last 4 weeks. I think you will find you will also get an EML light which will complicate matters and dealerships will automatically go to filers, flaps etc etc. The fix is a software downgrade or get a good ECU mapper with the older software.
I serviced a car last year and customer was sticking his car back to dealership for a simple recal. i said to him make a written request for no software update of any kind other than if required for the recal work (airbag). I took a log of the software before the recal and when he got it back it had a complete newer update. 4 weeks later EML light, fan running etc etc etc. This was definetely a software update fault.
But a smaller possibility on some cars is a faulty coolant temp/pressure sensor of some sort that will NOT always throw up a DTC. Temp or pressure goes out of spec concerning engine cooling then the following ECU procedure is engine fan. It costs nothing to replace coolant. Well not an expensive thing to do is what I mean. This is only my own experiences / thoughts on this so chucking it in here.

 

[Riverman]

A regen ONLY starts according to all the parameters being correct. Yes a petrol engine will get up to temp quicker. It is NOT NORMAL for any petrol or diesel car to constantly regen UNLESS the content goes high enough to kick in OR the pressure sensor is faulty. My guess is the cars doing it have been software updated with newer emmisions (lower) tolerances. Also a Mercedes will not regen if there are any DTC codes in the ECU.
I work on all types of german cars and find this is common more so with VW's since the recall to give them all software updates after the vw emmision crap stuff.
So mercedes have to follow the band wagon. update software and when they update it and lower the emmision tolerances what the manufacturers HAVE NOT DONE is replace the pressure sensors aswell as they are spec'd to go hand in hand with software from date of manufacture.
All the cars with this on running fan after engine off had got software updates within the last 4 weeks. I think you will find you will also get an EML light which will complicate matters and dealerships will automatically go to filers, flaps etc etc. The fix is a software downgrade or get a good ECU mapper with the older software.
I serviced a car last year and customer was sticking his car back to dealership for a simple recal. i said to him make a written request for no software update of any kind other than if required for the recal work (airbag). I took a log of the software before the recal and when he got it back it had a complete newer update. 4 weeks later EML light, fan running etc etc etc. This was definetely a software update fault.
But a smaller possibility on some cars is a faulty coolant temp/pressure sensor of some sort that will NOT always throw up a DTC. Temp or pressure goes out of spec concerning engine cooling then the following ECU procedure is engine fan. It costs nothing to replace coolant. Well not an expensive thing to do is what I mean. This is only my own experiences / thoughts on this so chucking it in here.

Dear HITECH
This is the best explanation of the over running fan that I have seen on here.

My car was registered in late December 2022. I assume it had this latest software installed. I bought it in June 2023. An ex dealer demo car 160 miles so had done only short demo drives. Most of my drives are now less that 30 miles which is when I noticed the problem.
After longer drives there is no problem at all and car shuts down quietly.