E350 Engine Overheating / AC Blowing Cool
Thread Starter
Newbie
Joined: Aug 2018
Posts: 7
Likes: 1
E-350 Sport Sedan
E350 Engine Overheating / AC Blowing Cool
Hello all,
Sometimes, but not always, when I have the AC on (blowing cool) the cooling fans will suddenly come on high, and the car starts to overheat. This is not in hot weather nor stop and go traffic.
Actually, it only happened twice. Once while parked, but the temp only climbed a little above what it usually is, but the electric engine fans were screaming loud. I shut it off and back on, and everything was okay again.
The second time while driving, but this time the temp went just about to the red line. I quickly shut off the AC and turned on the heat. The temp immediately dropped back down to normal.
Any ideas what's going on here?
Thanks!
Phil
Sometimes, but not always, when I have the AC on (blowing cool) the cooling fans will suddenly come on high, and the car starts to overheat. This is not in hot weather nor stop and go traffic.
Actually, it only happened twice. Once while parked, but the temp only climbed a little above what it usually is, but the electric engine fans were screaming loud. I shut it off and back on, and everything was okay again.
The second time while driving, but this time the temp went just about to the red line. I quickly shut off the AC and turned on the heat. The temp immediately dropped back down to normal.
Any ideas what's going on here?
Thanks!
Phil
Out Of Control!!
Joined: Apr 2019
Posts: 12,191
Likes: 6,888
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
round-robin
seems to me you were overwhelming the engine radiator cooling ability in both cases. What you observed was somewhat normal because of the extreme temperatures.
When you run A/C you are trying to cool your engine with already super heated air.
Hot ambient air heated by all the cabin heat is used to absorb additional heat... don't be surprised if the single fan goes screams until its bearing quits!
Warped heads are never out of question during overheat events. I am not 100% positive if Benz still use the amazing aluminum heads fasteners that were made famous by poping off the V8 ...
✌️
When you run A/C you are trying to cool your engine with already super heated air.
Hot ambient air heated by all the cabin heat is used to absorb additional heat... don't be surprised if the single fan goes screams until its bearing quits!
Warped heads are never out of question during overheat events. I am not 100% positive if Benz still use the amazing aluminum heads fasteners that were made famous by poping off the V8 ...
✌️
Last edited by CaliBenzDriver; May 2, 2021 at 02:37 AM.
Out Of Control!!
Joined: Apr 2019
Posts: 12,191
Likes: 6,888
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Last edited by CaliBenzDriver; May 2, 2021 at 01:32 PM.
MBWorld Fanatic!
Joined: Oct 2010
Posts: 5,142
Likes: 1,295
From: Southern US
2010 E550, 273 Engine: 2012 S550, 278 Engine
Hello all,
Sometimes, but not always, when I have the AC on (blowing cool) the cooling fans will suddenly come on high, and the car starts to overheat. This is not in hot weather nor stop and go traffic.
Actually, it only happened twice. Once while parked, but the temp only climbed a little above what it usually is, but the electric engine fans were screaming loud. I shut it off and back on, and everything was okay again.
The second time while driving, but this time the temp went just about to the red line. I quickly shut off the AC and turned on the heat. The temp immediately dropped back down to normal.
Any ideas what's going on here?
Thanks!
Phil
Sometimes, but not always, when I have the AC on (blowing cool) the cooling fans will suddenly come on high, and the car starts to overheat. This is not in hot weather nor stop and go traffic.
Actually, it only happened twice. Once while parked, but the temp only climbed a little above what it usually is, but the electric engine fans were screaming loud. I shut it off and back on, and everything was okay again.
The second time while driving, but this time the temp went just about to the red line. I quickly shut off the AC and turned on the heat. The temp immediately dropped back down to normal.
Any ideas what's going on here?
Thanks!
Phil
The fans running fast simply tells the engine and/or A/C needs more cooling power and when you turn A/C off and heat on and this drops the engine temperature it means that you have issue in the front of the car. Your engine radiator is not working properly and this is either because it is not filled properly with the coolant or you don't have enough flow thru the system. The third would be the fan problem but that obviously is working.
MBWorld Fanatic!
Joined: Jul 2008
Posts: 8,384
Likes: 800
2019 G70 6MT & 2022 Ford Maverick XL
Yep, make sure the coolant level is OK. You're not getting any warning lights? The thermostats in these cars are designed to stick OPEN which would give you a P0128 and the car would never warm up to normal temps, so it doesn't sound like that is the issue. Have you had any AC work done lately? Any work done to the coolant system, coolant added, anything? The engine fan is controlled by the computer and high AC pressure could be a cause. You might want to check the condenser - maybe it needs to be cleaned? Just brainstorming here.
I would get it scanned with a MB specific scanner just to see what it is saying. Even in extreme ambient temps, stop-and-go traffic, etc.. the car should not do this.
I remember a case from a few years back where an E-class kept having similar issues and it ended up being a faulty sensor.. I want to say it was a faulty oil temperature sensor, which was odd. I can't find the thread.
And yes, the cars will go into limp mode rather quickly during an overheat event.
I would get it scanned with a MB specific scanner just to see what it is saying. Even in extreme ambient temps, stop-and-go traffic, etc.. the car should not do this.
I remember a case from a few years back where an E-class kept having similar issues and it ended up being a faulty sensor.. I want to say it was a faulty oil temperature sensor, which was odd. I can't find the thread.
And yes, the cars will go into limp mode rather quickly during an overheat event.
Last edited by LILBENZ230; May 3, 2021 at 02:34 PM.
MBWorld Fanatic!
Joined: Jun 2020
Posts: 1,363
Likes: 1,012
'11 E350, '11 E550, '98 M3, '95 E320
Engine coolant temps will rise with A/C ON, especially when not moving or in stop and go. Yes, the fan will go 100% "screaming" t he higher the temp. All that's normal. When the OP says overheating... what was the actual temp? Even without A/C being ON, the car will try to maintain 80-100*C. Overheating is in the RED and not just a brief excursion.
That said, checking the obvious like has been stated is a good thing and scanning for any codes (with MB-specific code reader) as well.
That said, checking the obvious like has been stated is a good thing and scanning for any codes (with MB-specific code reader) as well.
