I have a C63s that I bought new in 2021. I am currently doing very low miles in it, and each journey is normally only 2 to 10 minutes. I haven't driven it on a run longer than 30 minutes for over six months. Due to other circumstances I am not able to take the car on a longer drive at this point in time.

For the past two months or so, I have noticed that after I switch off the engine, the fan runs for about 15 minutes at full speed and then 5 minutes at low speed. This happens now every time, even if I drive slowly 100 yards up the road and switch off. The engine is still virtually stone cold and the blue dashboard warning light is still on telling me that the engine is not yet up to temperature.

The other related problem is that all the fan running is flattening the battery and I am forever having to put it on the charger. Possibly the battery may be on the "way out" but this has only started happening since the fans have been coming on after switch off all the time. Previously I have had no problems with maintaining sufficient battery charge even though I am doing low mileage.

Any suggestions of why I am now experiencing this fan issue? I am aware that with normal driving the fans often come on when the engine is switched off to cool the turbos etc., but that is after the engine has heated up . I am having it happen in the middle of UK winter with a cold engine!

I read somewhere on some forum (can't find it now) where someone seemed to be having similar issues and it turned out that it was due to the petrol particulate filter, in that the engine software was needing to heat up the particulate filter to burn it off, but does not get a chance to get it up to temperature due the short drives, and keeps on trying. Does that make any sense? And how that is connected to the fans running is beyond me!

Can anyone help explain what's going on here?

 

That is a head scratcher for sure. I wonder if it will help if you use a block heater? You really want to get the vehicle to operating temperature that is for sure, condensation and stuff can't be burnt off and is bad. The engine oil will go bad quicker that way.

 

In regards to the battery, recommend using standby mode but only if you have a secure garage as it disables the auto-theft and all connections to Mercedes' servers. You also need to activate it everytime. Each time you hit the ignition it will reset back to normal mode.

 

In regards to the fan turning itself on and off for some reason I wonder if doing a reboot will help. Like unplugging the battery and all that stuff.

 

Another thing is I recommend scanning the vehicle if there are stored diagnostic codes. With a Mercedes capable scanner.

 

How to reboot: https://mbworld.org/forums/e-class-w...eboot-how.html

 

How to put the vehicle in standby mode: https://mbworld.org/forums/c63-c63s-...-function.html

 

Hope that helps. Be sure to post pictures of your ride : ) optional of course.

 

I hate to tell you, but that kind of short distance driving is not good for the engine. You are asking for all kinds of troubles down the road from fuel and moisture contamination in the oil to carbon build up on the valves.

You are also correct on the OPF. It periodically has to burn off the trapped particles or it will eventually clog up. This is done by raising the exhaust temperature temporarily, but yes if you never drive in a way that even fully warms up the engine you will eventually have to have it cleaned manually.

Not particularly sure what's going on with your fan, but yes your engine might try to heat itself up enough in a short time to start the OPF burn cycle, but then you quickly park the car again, so it has to get rid of all the extra heat.

As for the battery, there are multiple concerns here. The fan running won't help, but all those frequent engine starts will drain your battery w/o the sufficiently long drives to replenish it. The starter motor uses a lot of juice, so you have to drive enough to recharge. At 4-5 years, the AGM battery is also starting to reach its end of life. I just changed the battery in my 2019 due to age.

I know life sometimes doesn't go as planned, but this is not the car to drive for 2 minutes and then park it again. I don't take mine out for short drives. I either walk, ride my bike or take the wife's normal car if I need to run a short errand for which I need a car. We both work from home, so neither of us drives very much, but her car is now 20 years old with a lot less fancy engine tech, so short distance driving isn't a problem. Your kind of driving would be perfect for an EV. No worries of having to warm up the engine, dealing with an OPF etc. It'll happily drive 2 minutes at a time without any issues.

 

Ya exactly, OP can't even enjoy the V8 properly when the oil temperature never reaches the operating temperature.