overheating or normal operation?
 

My 1994 E320 wagon was running quite hot yesterday, the first 70+ F day in a while around here. A few questions:

1. What temperature is the unlabeled hash mark that is right above the labeled 80 C hash mark? Is it 100 C or 90 C? My needle was in between the top white hash mark (120 C) and the unmarked hash mark. The car has a relatively new OE water pump and the car is in very good running condition.

2. Do the auxiliary fans only come on when the A/C switch is engaged?

The mark above 80C is 100C. The aux fans will at least be on low speed with the A/C on in traffic when the pressure is high enough. The fan clutch should be locked by 96C or so.

How hot exactly was it and how long were you sitting in traffic? The temp that your car was running at was 110C

i suppose with the warm weater coming on, there will be a few of these questions. that first line above 80 is 100 degrees. the auxilliary fans will kick in above that at around 105 - 107. under normal conditions, the M104 engine normally does not get up to the 100 degree mark but stop and go driving will do that. after running at highway speeds even some mild stop and go will get it over the 100 mark.

in answer to your second question - the aux fans will turn on at low speed when the A/C is on. it switches to high speed when the temps reach 105 - 107.

DTF,

If you run a search, you will find that these cars run pretty hot. Yes its very alarming to see the temp between the hash mark you described.

Let me do a search...and tell u whats up. I clearly remember a post regarding the AC and auxilary fan.

From what I've seen on my car....its pretty stays @ 80 or just above as I drive with the A/C...but when I stop the temp rises above the hash after 80..actually mid way to 120.

Then I went for a 20mins run with full A/C running @ 75mph with a ambient temp of 72.

Then I drove home....opened the hood....only 1 fan was on but the temp was still the same.

Let the car sit for another 20mins...same thing. The temp never went any higher.

-Ren

<<1. What temperature is the unlabeled hash mark that is right above the labeled 80 C hash mark? Is it 100 C or 90 C>>

All the hash marks are at 20 C. increments, so any unmarked hash is 20C higher than the preceding marked one.

Thanks to all for the prompt response.
Ali: I was driving from stop light to stop light in city driving - not really heavy traffic, always moving unless at a red light. Temp goes back to normal on the highway. Could it be the thermostat? Sounds like the temp thing could be the cause of the wiring harness faiures in these cars in the past.

I have a 300E and for the past few weeks it's been running much hotter at stoplights and over all traffic, so i replaced the thermostat and everything is fine now(runs around 75-80c)...This is a DIY job, very very easy, and there only $30 from the dealer.
Good luck:D :D

if you don't want your temps to see 100 degrees, check this thread out:

modifiying auxilliary fan cut in point

i am curious about that 75 degree thermostat that you can get. anyone have any opinions on this, maybe Arthur?

Problem with powering the thermo is the chances of not running correct heat under normal conditions.

Having played around with this for a while, a couple of my thoughts and observations.

The first that comes to mind is although Benz has told us so many times that these traffic and low speed temps are to be expected and should cause us no concern, I have noted that they have changed the newer aux. fan system to include a
cut in for low speed fan that now is switched by both a/c pressure AND engine coolant....so that tells me something.
[ and something I am working on]

Second, note that they have switched to an electric fan in favor of viscous.
Remember , viscous is supposed to help out before aux., but when we need it the most [ stop light- high heat load], even
if it is locked up, it is only turning at idle speed [ Well, laady-daah]
And I'l be damned if I can tell if these things are slipping at low speed. [ Notice that if you are in a high temp situation at a stop and you go to N and give it a little Rs, the temp drops right down. Well, is that the viscous finally doing some good or are we just incresing coolant flow [ prob both]
As far as thermostat , we seem to be already up to factory spec full open and I have verified this , so a lower thermo is prob not going to help the overall condition [ which is leaning towards a border-line effecient system].
I am confident they are correct that these high running temps are OK, but I don't like them over 100....

OOOpps 1
Joe ,
I meant "Lowering " the thermo, instead of " Powering" it...
but after looking at it for a while, maybe that's the Ticket.,,
We should "POWER the Thermo" !!!
What the hell, we fooled the ECU with the aux fan switch resistor, now we can fool the thermo with some electric heater
element [ maybe an old 4 wire O2 sensor] ...
Sooner or later we will get it , but with all the mods , we might have to up the system to 24V........:)

hi Arthur,

i thought the same thing about that thermostat and didn't go for it. i am using the 1.5k ohm resistor right now and the max temps are a wee bit lower than when using the 1.8k and i do seem to notice that the fans kick in more often. i'll keep it this way for the summer and switch to the higher one in winter.

cheers

Pardon my ignorance here but how does one go about verifying the viscous fan couple is properly operating?

Jeff