2010 E350 CDI Cooling Fan Issue

Michael168

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2010 E350 CDI Estate 3000cc
Hi all. Apologies for my first post being such a long one but I am hoping somebody on here may be able to help me with the latest problem on my car. It is a 2010 E350 CDi Estate and i have an issue with the cooling fan. I have been through all the other cooling fan posts on here but can’t find one the same as mine. I have been doing some investigating and i will try and include as much information as possible.

1st Start of the Day - On the first journey of any day (and only the first journey) the car runs well for 7 to 8 miles. The temp gauge starts to rise but when it gets to approx 60 degrees Celsius (7 or 8 miles) the gauge suddenly drops back to 40 degrees. When you stop the car you can hear the cooling fan running at full speed. This will continue to run at full speed no matter how many more miles you drive (i tried for 50 miles), however, if you switch off the ignition and restart it the fan stops and doesn’t come on the fast speed again. However, what it does do it run at a reduced speed all the time you are drinking it so the temp never gets above 60 degrees.

2nd, 3rd or 4th start of the day - The cooling fan will run constantly but at a reduced speed (AC on or off) al the time you are driving it. The temp gauge never gets above 60 degrees unless you get stuck in stationary traffic.

Whilst stationary - whilst the car is stationary and just ticking over the fan does not run (unless you have the AC on) and it warms up as you would expect. When it gets up to temp the fan cuts in and then once it heads cooled it down the fan cuts back out. However, if at any point you give the car a single rev this starts the cooling fan running. If you then let it idle agin the fan stops after about 30 seconds, unless you rev it again. Each time you rev it the cooling fan starts.

What have i done so far? - 6 months ago the fan started running constantly. This was traced to the AC pressure switch which was replaced and until a week ago it behaved perfectly. I have checked the fault codes with an iCarSoft and there are no faults showing. I have removed the ECU (driver’s wheel arch) and checked for water ingress and cleaned the connections. I have checked the connection on the AC pressure switch and given them a clean. I have removed the cooling fan, checked and cleaned all the connections and checked the wiring for any damage. I have also cleaned the ambient air temp sensor behind the front bumper. The AC appears to be working correctly and the temp sensors (coolant and exterior) look to be measuring correctly according to the live data on the iCarSoft.

I am half suspecting that the fault could be the fan controller but i don’t want to just buy one only to find it isn’t the issue, especially as i’ve Seen a couple of posts about ECU problems. Is there any way to check the fan controller without just replacing it?

Apologies for the very long post, but i am hoping with the detail above that somebody may be able to point me in the right direction. I love the car but this is driving me insane and i really need to fix it. It gets annoying having to pull off the motorway after 7 miles just to switch the car off and back on again to stop the fan running at full speed for the whole journey.

Thank you in advance.

Michael
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sensor555

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hi, im no expert on this but my E350 cdi 2010 w 212 runs at 90 Deg. C. after about 3 miles. Could it be a thermostat problem.
 
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Michael168

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hi, im no expert on this but my E350 cdi 2010 w 212 runs at 90 Deg. C. after about 3 miles. Could it be a thermostat problem.

Hi. Thank you for the reply but it’s because the cooling fan is running all the time which is why it’s not warming up.
 

Avnt

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Mercedes c350 cdi estate amg
Hi. Thank you for the reply but it’s because the cooling fan is running all the time which is why it’s not warming up.

On my C Class the fan was running all the time because the air con pressure wasnt correct.


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mioba

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Sounds like a stat issue to me. Stat failing to open, leading to innapropriate temp readings, leading to fan kicking in. Thats just speculation of course.
 

oigle

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Hi. Thank you for the reply but it’s because the cooling fan is running all the time which is why it’s not warming up.

Not so. The thermostat should remain closed until correct temp (circa 90°) is reached, regardless of fan operation. The thermostat should then open and control the temp at the above mentioned figure. The fan continuous operation is a separate issue as suggested by others.
 

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