Randomly Overheating
My vehicle, 2009 Mercedes Benz E350 W211, randomly overheats with
“Overheat icon” on the center dash display, and has been for nearly two
months now. I had an engine misfire on the interstate around this two month
mark as well. I have spark plugs and ignition coils to put on the vehicle still. I
haven’t had an engine misfire since this time so I’ve held off on this
installation, but plan to do so in the coming weeks.
When this “overheat” occurs, the Engine Temperature gauge goes from
80 to 95 then to 75 then back to 80 rapidly all within a few seconds
repeatedly. It can be stuck in this loop for a few seconds to almost a minute
at times. It's very difficult to recreate this situation as I have tried to, and
seems to go away randomly as well. It has happened when stopped at a
light, slow traffic, on the interstate going 80mph.
I used to think it was an AC compressor going out or malfunctioning
when it would “overheat,” because I would have the AC on in the car and it
seemed like it would trigger this “overheat” a bit after running the AC for a
while at operating temperature. I then noticed the AC not being as cold as
before, there was no flashing light indicating low freon (I believe that’s a
flashing air recirculation button light), but I still checked the levels with
gauges and all seemed okay. There was a light clicking that seemed to be
coming from the compressor as well when the “overheat icon” would show
on the dash once as well, and it seemed to be coming from the AC
Compressor(only occurred when the icon would flash on my dash), but I’m
not 100% sure.
I still went ahead and still drained the Freon because the levels hadn’t
been checked in the 3 years I’ve had the vehicle, then also vacuumed out
any moisture and proceeded to refill the compressor with Freon, but it won’t
take any. So that leads me to think the AC Compressor is on its way out
because it isn’t accepting any Freon and charging up?
Come to find out later though, the “engine overheat” still does happen
when the AC and blower is off as well when out driving though too. I know
this 2009 E350 has a clutchless AC Compressor so it’s always running, so
could this still be an AC Compressor issue? I have a new AC Compressor,
Accumulator/Drier, Expansion Valve coming in over the next few days to see
if that could be the issue I’m having.
The only recent work I have done on this vehicle is replacing the
Thermostat and Upper Radiator Hose, as well as the Temperature Sensor on
the rear of the engine block. The Thermostat and Upper Radiator Hose were
replaced almost 6 months ago over the Winter, and the Temperature Sensor
on the block was replaced about a month ago. I currently have PEAK 50/50
Antifreeze in the vehicle as well after flushing the coolant.