C43 Cooling Fan Issue

[Wisherw]

Hi
I have a facelift C43 and am struggling to love it! The latest issue is the cooling fan staying on when I switch the car off. This was happening in winter and after driving the car very gently so took it to MB who fixed it. It’s happening again and the petrol consumption also increases when this happens. I’m not driving hard, sitting in any traffic and the weather is cool so something isn’t right. Anyone else had this issue or got any thoughts? Many thanks

 

[Steve84N]

Most likely a dodgy thermostat or the coolant isn't circulating properly due to a poor pump or air in the system.

 

[Wisherw]

Most likely a dodgy thermostat or the coolant isn't circulating properly due to a poor pump or air in the system.

Thanks, can’t understand how MB can sort the issue and then it happens again? Cheers

 

[Blazer]

You could try taking it back to MB on the basis that it has started doing it again within a year??

 

[Mike9999]

Did this ever get fixed , as I’ve noticed mine has done this today and yesterday ? Wondering whether to contact the dealer

 

[mattgod69]

My C43 has also started doing this lately.... could it be due to the cold weather? Mine is a 68 plate. I noticed it stays on for a few mins when I turn the engine off. Cheers. Matt

 

[sgregory124]

For people with the problem, are you certain that this isn't by design behaviour? My previous car (Audi A6) would run the fans after engine switch off frequently, it wasn't ambient temp dependent either and would happen on cold days as well as warm. It was done to cool down certain components after shutdown. It usually ran on for 5-8 minutes then went off by itself.

Nothing to worry about i'd say.

 

[Mike9999]

I've stopped worrying about it now - it only lasts a few minutes - and my other car does it as well. So will just leave it

 

[cws196]

I've heard of VAG diesels with similar behavior and it's apparently for cooling of DPF/emissions control-related parts. Pure speculation but could facelift C43 engines be doing this as they now have an OPF fitted?

 

[Swiftos9]

Hi
I have a facelift C43 and am struggling to love it! The latest issue is the cooling fan staying on when I switch the car off. This was happening in winter and after driving the car very gently so took it to MB who fixed it. It’s happening again and the petrol consumption also increases when this happens. I’m not driving hard, sitting in any traffic and the weather is cool so something isn’t right. Anyone else had this issue or got any thoughts? Many thanks

This has just happened to mine but in reverse bizarrely!!! The fan has always come on when I turned the car off after a drive and MPG was rubbish. The last week fan no longer comes on when I turn the car off and MPG has improved significantly. I assumed the fan was coming on to cool the turbos even though the engine temps were always ok.

 

[Swiftos9]

Further update on this. My fan has today came on again when I switch the engine off and MPG has dropped. I have also noticed the gearbox is dropping down from 9th to 8th when cruising on the motorway at random times! Never done this before. Think I’ll book it in to get looked at as something is not right. For the last 3 months the car has been great, smooth and good MPG (if I drive it careful!).

Anyone else had this issue??

 

[Germgh0st]

My fan is on for a few mins after I switch the car off, it's done this from new. I assumed it was normal, my Focust ST used to do the same.

 

[vijilants]

The over running of the cooling fan used to be a design feature on turbo equipped cars. When when you switch the engine off, the engine actually gets hotter due to the fact that there is no coolant circulation and there is no quick heat dissipation under the bonnet. So, to protect the turbos, they used to over run the fans after the engine was switched off.

 

[Swiftos9]

The over running of the cooling fan used to be a design feature on turbo equipped cars. When when you switch the engine off, the engine actually gets hotter due to the fact that there is no coolant circulation and there is no quick heat dissipation under the bonnet. So, to protect the turbos, they used to over run the fans after the engine was switched off.

I understand the point about fan staying on to cool things down when you have switched the car off. The issue for me is the fan used to come on every time I switched the engine off, then about 3 months ago the fan stopped coming on, but also the mpg increase by about 25% and the car was a lot smoother through the gears. Just drove better and in my mind how it should be. This was great, but two days ago the gear shifts aren’t as smooth and the mpg has fallen by 25 - 30%. It just feels a bit jerky on cruise now. I do the same run to and from work every day, same roads et. so I know when the car is not right. This is not right. I did the gearbox reset but it’s made no difference. I’ll book it in to MB to have it looked at as something ain’t right.

 

[vijilants]

I understand the point about fan staying on to cool things down when you have switched the car off. The issue for me is the fan used to come on every time I switched the engine off, then about 3 months ago the fan stopped coming on, but also the mpg increase by about 25% and the car was a lot smoother through the gears. Just drove better and in my mind how it should be. This was great, but two days ago the gear shifts aren’t as smooth and the mpg has fallen by 25 - 30%. It just feels a bit jerky on cruise now. I do the same run to and from work every day, same roads et. so I know when the car is not right. This is not right. I did the gearbox reset but it’s made no difference. I’ll book it in to MB to have it looked at as something ain’t right.

Best get it plugged in to the Star Xentry diagnostics system and have the codes read. You never know, there may be a software update which will sort it out.

I havn't noticed a fan overrun on mine that I can remember, however I am out in it later today and will check.

 

[Swiftos9]

Further update. Still getting awful MPG and fan coming on when I turn the car off after a long run. Went into MB yesterday, they checked it over and could find no faults. They said sometimes the fan comes on and could find no issues with the fan. All they did was plug it in the computer and checked for faults and that it had all the latest software updates. Told them something is not right. If I drive in Individual mode with every thing paired back and not going over 60mph I can’t get above 29mpg on a 35mile motorway run!

MB have asked me to take the master tech out in it tomorrow to show him how it behaves and the awful mpg. Will update you on what they say, I’m not hopeful this will get resolved!

 

[Germgh0st]

To be fair 29mpg isn't that bad, I drove to Ripon and back from South Shields last weekend and that was part motorway part single lane roads and I averaged 28mpg, driving mainly nicely with the odd bit of fun. Best I've had from a long (100 miles +) motorway run is about 33.

Not sure why you would choose individual mode with everything pared back and not just use comfort - it's the same?

I think it's maybe not the cooling fan that's your issue but rather your MPG expectaions?

 

[vijilants]

I can’t get above 29mpg on a 35mile motorway run!

As per Germgh0st, 29mpg is about right. I've never seen above 30, 32 mpg and thats driving in Eco mode mainly motorway with very light throttle movement when we had the fuel shortage.

After all, it is a 3 litre twin turbo, tuned for performance so I wonldn't expect high mpg figures.

Personally I am super happy with the mpg figures I get as I actually expected a lot less when I bought this car.

If it is economy you are after, forget about buying AMG engined cars. They are primarily designed for performance, and not enconomy. Getting heavy on the right foot on occasion is irresistable as that is what they are about. and that costs petrol

 

[f17ant]

If it helps my friends C43 is only slightly better on petrol around town compared to my C63 (both driving like granny’s I can get 20mpg and he will get 22)

 

[Swiftos9]

As per Germgh0st, 29mpg is about right. I've never seen above 30, 32 mpg and thats driving in Eco mode mainly motorway with very light throttle movement when we had the fuel shortage.

After all, it is a 3 litre twin turbo, tuned for performance so I wonldn't expect high mpg figures.

Personally I am super happy with the mpg figures I get as I actually expected a lot less when I bought this car.

If it is economy you are after, forget about buying AMG engined cars. They are primarily designed for performance, and not enconomy. Getting heavy on the right foot on occasion is irresistable as that is what they are about. and that costs petrol

It’s juts strange that I was getting upto 39mpg which was great! Good to know people are getting the around 29mpg, I knew what I was buying, just strange that I was averaging 39mpg in eco mode which gave me a false sense of economy!!!

It’s not the end of the world to be fair but will keep you guys posted on how things go.