It seems like this is a popular topic lately. I would like to know what temp the other other members cars at running at. Please give us your model, temp, ambient temp and both data for traffic driving and freeway driving:
My W124 400e:

in traffic:
ambient_temp coolant_temp
65 F 85 C - 100 C

Freeway:
65 F 70 C - 80 C

Does this seem normal?

Hey neighbor!
'89 300se
65-98 F ambient runs 80C city and freeway.

'95 c280
65F ambient runs 85C approx to 90C approx. in
city and 80C on freeway.

The 300se has more open space under hood for
ventilation and does not retain the heat
so long after shut off.
The c-280 is cramped under hood and gets HOT
in there as well as retaining heat long after
shut off. This is probably one reason that the
wiring harnesses begin to deteriorate besides
poor design of insulation.

Maybe your radiator needs renewing of fluid
with less antifreeze.
Try redline waterwetter combined with less antifreeze in the mix.
Keep an eye on it!

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1979 300D
133K miles
1989 300SE
1995 C280

My 1984 300D runs as follows:

Outside temp 100F, engine 90C (then up to 105C at idle);

Outside temp 78F, engine 78C...

or thereabout.

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Matt
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Grey/black '84 300D, 194K

Ditto what Zoonhollis posted' on my 83 300D 185K miles

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Keith Schuster
99 Harley Davidson Ultra Classic
97 Dodge Ram
83 300D
Heavy equipment\hydraulic mechanic 20 yrs

Hey Rabbit,
I'm just down the highway from you a bit in Santa Cruz. My '86 300e runs at about the same temps as your 400e does. If I let it idle too long parked, it starts to really heat up.


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Kyle De Priest
1986 300e
1972 BMW R75/5 (Best there is)

My question is about ambient temparature. I would have thought that regardless of the outside temp, the coolant temp should be more constant and not be as affected by the ambient. Perhaps I am way off base here. Anyone have any good scientific or simple explanation for this? Thanks everyone for answering these questions. The engineer in me just does not want to let this rest.

FYI, my friend in Hawaii has a 99' e430 and it always seems to run about 85-95C no matter what he is doing. The temp in Hawaii is always around 70-80 F.

Well, let's take a look at thermodynamics. Thermal energy will flow from hot to less hot or cold if you will. If you have two objects at the same temp sitting in close proximity, nothing will happen. If one is cooler than the other, the the hotter of the two will transfer heat to the cooler object until both are at equilibruim, so, if you have a car with a cooling system at operating temp, the heat transfer will be affected by the temp of the other part of the system, namely the ambient air. Now we all know that it's much nicer to have a fan blowing cool air in your face rather than hot air. IF the air is dry and you're sweating, the evaporation of the sweat will help cool you down. If the air is damp, we all know what that feels like. Could be they called the evaporator in A/C systems that name for that reason. At any rate, when, the air that is "cooling" your engine is almost as hot as the coolant air interface AKA radiator, very little heat transfer is going to take place. If the ambient air is cooler or cold, you will get a much imporved heat transfer. That's why we have thermostats. We all know it takes a bit longer in the winter to get things up to operating temp, when in the summer on a 100 degree day, the car is at operating temp by the time you roll down the window. Anyway, when it's hot out, the cooling system has to work a lot harder to move the heat than when it's cool. This is directly related to the ambient temp of the air passing thru the radiator and the condenser. BTW, why do you think the condenser is in front of the radiator?? 50 points for the correct answer...

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE

I've got all you guys beat regarding the coolant temperature readout. This is on my 1995 S420.

On the Freeway, things look OK:
With ambient temps <80 degrees F, my readout is usually at 85 C. Above ambient temps of approx. 85 F, I'll have my A/C on, and I'll see gauge temps of 85-95 C.

In Traffic:
With ambient temps <80 degrees F, my readout is approx. 85-95 degrees C. I think I've seen readouts as high as 100 C (No A/C). Above ambient temps of 80 F, with my A/C on, I regularly see gauge temps of 95-100 C. Above ambient temps of 90 F, A/C on, my gauge readouts commonly show 110 C. This is where I think that either the coolant temp is too high, or the gauge is reading higher than the actual temperature. My auxillary fans click on at 110 C gauge. But like all late-model M-B's I've observed, the fans blast for about 15 seconds, then shut off for awhile. The fans repeat this short cycling period. My fans shut off before the temp readout drops below 110 C. I'm sure this sounds familiar to many.

Let me quote a clipping I keep in my M-B service folder. It's from Popular Mechanics magazine, "Car Care", "Service Tips", April 1996: "All M-B cars may indicate hot temperatures (up to the red zone) while under a heavy load or stuck in traffic. This is normal and no cause of concern."

I repeat this to myself when I see 110 C on my coolant temp gauge. It helps somewhat.

Mike

In two years my engine temp guage has only gone above 80, when I've done Italian tune ups (short bouts of high rev driving in lower gears). It went up a little over 90 then. Other than that longest trip I've taken was 22 hours of straight driving in temps around 80 degrees (This is Canada after all) Temp never went over 80.

JP

Very good reply macS420. I will repeat that to myself evertime the temp reading goes above 100C. no harm, no harm... yikes!

It is a little errie. And yes, my temps does go to about 95-100C when the ambient outside is 85F and above.

My car runs around 90-95 deg C in normal driving and 95-100 with the AC running. This does seem a bit high to me, although I did have my thermostat changed a while back. Prior to this, it took an 8 mile drive to get it to 80; it would warm up only to 60 degrees after a few miles. I guess I should be happy that I'm getting warmed up fully; mileage at 60 deg C was about 5 mpg worse than normal. My '77 300D held 80 deg. C constantly unless the AC was on.

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Robert W. Roe
1984 300SD 173K mi

Mine constantly running any where from 85C up to 110C.....there shouldn't be anything to worry about as long as the needle doesn't hit the red zone of the guage....

Andy Kuo

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• 1992 Mercedes-Benz 400SE
  
• Pearl Grey/Black Leather
  

ICQ#26950002
Mercedes Owners ICQ ActiveList ID#61730549
Mercedes S-Class Page
http://akry.homestead.com

well i am always wondering about running temps, my 82 300D has been running at 100 Celcius since i bought it, and lately at about 105. i'm not sure if thats healthy tho.

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Maciej Jamrozek
Born in '82
'82 300D TurboDiesel 500+K

My R129 always at 95 with AC on regardless of the ambient temp. Occasionally it will get up to 100 or 105 when in city traffic. Whereas my ML always at 85 regardless of hte ambient temp (summer or winter has no effects on the reading). I often wonder if my R129 is running too hot. It will be great if someone can tell us what is the optimal range of operational temps are.

95 R129
98 ML320

The 300SD runs at 85C. On the rare occasions I can go faster than 70mph on the freeway, it creeps up slowly. If I try to sustain 80-85mph it creeps to 90; I haven't gone fast enough long enough to see if it keeps going up.

The E300 Diesel stay rock-steady at 85C. (I was going to say it was "Like a rock" but that's another brand and another forum...

None of the cars exhibit variation with outside air temperature.

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'96 E300D 60k mi (wife's daily ride)
'95 Audi 90 120k mi
'92 GMC Suburban 139k mi
'85 300SD 234k mi (my daily ride)