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1997 E320 Elegance- 140,000 miles, Black with Interior 204 (Leather, Saffron/Java)
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448 Posts
Discussion Starter #1
Hello all...

Chasing after what seems to me to be an anomaly in my engine temps (97 e320). Just put on about 300 miles driving up to seattle and noticed some things...Driving down longer mountain grades at about 70f the temp on the ac diagnostic mode showed as low as 175f (79.5c).

Going uphill it would warm as high as 188f or 190f (86.7c/87.8c)

On the freeway at 75mph with the A/C off it sits around 184-186 (fell once to 182) or 83-86c...AC on adds about 2-4 degrees.

Sitting in traffic or at lights is what concerns me...I can pull up to a light at 186f and by the time the light turns green I can be running at 195f (91c)...I've even seen it as high as 200f (93c) and that's in 78-85 degree weather...

Is that kind of variation in temp. normal on the M104? I've never had another car vary by that much and it seems to me that constant changes in temp is how head gaskets get killed.

I've looked at the thermostat, it's good...fan clutch is good. Aux fan works as advertised and has a new belt so it's good...
 

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1999 E430; 2005 ML500
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1,687 Posts
Sounds like my M113 in hot weather with AC on. Idling there just isn't enough flow to get great heat transfer, so temps increase. Your temps are completely within normal range. When it gets really hot, your aux fans kick in.

Note also that most / many other modern cars don't have real temp gages anymore anyway. Se http://forum.chryslerminivan.net/showthread.php/15711-Does-temperature-gage-gage
 

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Outstanding Contributor Always Remembered RIP
216 with everything. 2002 SL500 with everything. 2009 SL500 with everything.
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6,543 Posts
That sounds normal to me as well and just fine :)
 

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E320/E250 Bluetec Ford F350 6.7l
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36,707 Posts
Just to avoid such question most of manufacturers will put "dummy" gauges on the dashboard. It looks like a gauge with a scale, but will not show you any change until you go to extreme.
I consider 79-85C variations normal, as that is the range most of thermostats start to open to full opening. Anything above that is indication that the radiator is at full load and needs help from the fan for cooling. I drive my diesels with engine fans removed.
 

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1997 E320 Elegance- 140,000 miles, Black with Interior 204 (Leather, Saffron/Java)
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448 Posts
Discussion Starter #5

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1997 E320 Elegance- 140,000 miles, Black with Interior 204 (Leather, Saffron/Java)
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448 Posts
Discussion Starter #7
You thermostat is most probably about to die
Guess you missed the part where I said I tested the thermostat and it's good. Plus, it's only 6 months old anyway.
 

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E320/E250 Bluetec Ford F350 6.7l
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36,707 Posts
So what do you do when you inevitably have to stop moving?
Keep the engine running with AC at full blast :D
I did full test a week ago driving in 98-102F temperatures. At 70 mph the engine would stay in 78-82C range. In the city it went up to 96C, but left idling (electric fan on low) it dropped down to 92C after some time on parking lot.
 

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C180 1995
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7 Posts
The stat should be sensitive enough to absorb the temp variation almost in real time. So it is not easy to test if it operates as it should. The same concept applies also for the viscous fan.
 
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