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  #1  
Old 08-24-2003, 07:17 PM
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300E runs hot with A/C on....HELP!!!

Hello Board,

I rarely use my A/C, but today I decided to use it(it was really hot). My temp is usually about 85-90 C . Well I turned on my ac and right as I got into havy traffic the temperature started to climb. I went all the way to about 110 C. Well I had my expansion tank and cap replaced and I also had the cooling system flushed. My cooland/water mixture is a perfect 50/50. I have no leaks, What could have caused my car's temp to run so hot???

Do I need a new thermostat??? If so, what kind? a colder or hotter one???

Help!!!
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1987 mercedes 300E
1995 e320 conversion(hated the 300e grill)
HID/Xenon (D2S)
Keyless Entry
Monochromatic Paint (Custom Blue)
Smoked Tails
Flat Badged (front)
Debadged (rear)
custom "carbon fiber" console
18 inch HP EVO rims
Sold! Now I drive a Monte Carlo SS
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  #2  
Old 08-24-2003, 07:46 PM
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Location: Evansville, Indiana
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110 C is a bit hot, but not catastrophic. Check the operation of your aux fan (does it run with the AC on or not? It should). It should also come one at 100C, and the visco clutch should lock up and cause considerably more noise when then engine is that hot.

Usual culprit here is a bad visco clutch, closesly followed by a bad connection on the resistor for low speed aux fan operation so you don't get a fan until 100C.

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Last edited by psfred; 08-24-2003 at 08:16 PM.
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  #3  
Old 08-24-2003, 08:55 PM
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Join Date: Nov 2001
Location: North Central Kentucky
Posts: 1,065
I'm not sure the temp, but somewhere along the line, your a/c Compressor should shut off and the AUX fan come on. This is controlled by a temp. switch on the head. It has two connectors on it. one two wire and one with only one wire. The plastic in the sensor is probably green. Thing went bad on my daughter's car. A/c would not work and fan ran whenever the key was on. Pain in neck to change. You have to pull the valve cover to get a wrench on it
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  #4  
Old 08-25-2003, 06:54 PM
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I forgot to mention that I have a brand new aux fan. Could it be the thermostat???
__________________
1987 mercedes 300E
1995 e320 conversion(hated the 300e grill)
HID/Xenon (D2S)
Keyless Entry
Monochromatic Paint (Custom Blue)
Smoked Tails
Flat Badged (front)
Debadged (rear)
custom "carbon fiber" console
18 inch HP EVO rims
Sold! Now I drive a Monte Carlo SS
http://memimage.cardomain.net/member.../352975_67.jpg
http://memimage.cardomain.net/member.../748335_24.jpg
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  #5  
Old 08-25-2003, 09:51 PM
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Location: Evansville, Indiana
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Could be, but if it is, it will get that hot without the AC, too, generally.

Does your aux fan actually run (new or not, if ti ain't spinning, it ain't movin air....).

How old is the radiator?

Does the visco clutch work (do a search).

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #6  
Old 08-30-2003, 12:45 AM
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I replaced the thermostat today. It helped a lot. The highest the temp reached was 105 C . I am still looking into what could be the culprit of this problem. My car usually ran at 90 C on a hot day with the AC on high.
__________________
1987 mercedes 300E
1995 e320 conversion(hated the 300e grill)
HID/Xenon (D2S)
Keyless Entry
Monochromatic Paint (Custom Blue)
Smoked Tails
Flat Badged (front)
Debadged (rear)
custom "carbon fiber" console
18 inch HP EVO rims
Sold! Now I drive a Monte Carlo SS
http://memimage.cardomain.net/member.../352975_67.jpg
http://memimage.cardomain.net/member.../748335_24.jpg
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  #7  
Old 08-30-2003, 02:19 AM
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Join Date: Mar 2003
Location: Southern California
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As these cars age, the radiator tubes develop internal deposits, which reduces their heat exchange efficiency. Significant deposit buildup would be normal if the cooling system has been serviced with conventional green antifreeze.

If the car has only been serviced with MB antifreeze or Dexcool, deposit buildup will be less because these formulations either contain no inorganic salts (Dexcool) or a very minimum amount (MB brand). Though inorganic salt formulations can be effective in controlling corrosion, they precipitate out and clog the tubes.

The engine driven fan clutch should nearly lock at about 100C and you should hear fan roar above about 2000 revs. The electric fans should activate at high speed at about 110C. If fan operation is normal, the most likely culprit of consistent hot running is probably a loss of radiator efficiency due to deposit buildup.

Duke
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  #8  
Old 08-30-2003, 12:14 PM
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Duke hit the nail on the head.

How often do you read here where someone replaced anything/everything related to a 15 yr. old cooling system only to still have an overheating problem.

Internals start clogging over time and head gaskets develop slight leaks which cause pressure loss, followed by increased temps.
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  #9  
Old 08-30-2003, 03:41 PM
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Location: SOUTH JERSEY
Posts: 196
Thumbs up same prob here...

have a 92 turbo diesel with same problem however alldata site sez the following in a T.S.B. mind you this is for a 92 turbo diesel

Cooling - High Coolant Temperatures

MD-NET ADMINISTRATIVE MESSAGE

DATE: JULY 22, 1994

MESSAGE #: 322

TO: ALL DEALER SERVICE MANAGERS / ALL DEALER PARTS MANAGERS

SUBJECT: GROUP 20 - ALL MODELS, COOLANT TEMPERATURES


The coolant temperature of MB vehicles may rise substantially above 100C/212F at high ambient temperatures while the vehicle is:

a) stopped
b) in city traffic ("stop and go")
c) when driving uphill
d) when driving at very high speed, i.e. with high engine load


Engine coolant temperature returns to "normal" upon returning to regular driving conditions. In individual cases, the temperature reading may approach the red field of the temperature gauge.

Provided the cooling system is well maintained and in good working order, such temperature levels do not create any danger for the engine and, therefore, give no cause for concern. The boiling point of the recommended coolant mixture (Refer to Service Information 20/9 and Service Microfiche group 20), is much higher than 1OOC.

Copyright 2003 ALLDATA LLC
Terms of Use
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1994 S-350 6cyl Turbo Diesel 158k

1998 300d 6 cyl Turbo Diesel 143K

1993 2.5 124 Turbo-Diesel 236

1990 2.5 124 Turbo-Diesel 228k

1983 SL-500 EURO W/HEATED SEATS 40K

SOLD 1977 Jaguar XJ6 Coupe Antique Roadster 85K

SOLD 1993 2.6 6 cyl 190 E 150k

SOLD 1992 2.5 124 Turbo-Diesel 204k

RIP 1992 124 300 TD 265K OIL PUMP QUIT @ 85MPH
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  #10  
Old 08-30-2003, 03:45 PM
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Join Date: Jan 2003
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..

REMEMBER THAT INFO WAS FOR A 92 2.5 TURBO DIESEL
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1994 S-350 6cyl Turbo Diesel 158k

1998 300d 6 cyl Turbo Diesel 143K

1993 2.5 124 Turbo-Diesel 236

1990 2.5 124 Turbo-Diesel 228k

1983 SL-500 EURO W/HEATED SEATS 40K

SOLD 1977 Jaguar XJ6 Coupe Antique Roadster 85K

SOLD 1993 2.6 6 cyl 190 E 150k

SOLD 1992 2.5 124 Turbo-Diesel 204k

RIP 1992 124 300 TD 265K OIL PUMP QUIT @ 85MPH
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