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Old 06-28-2011, 03:35 PM   #1 (permalink)
BenzWorld Member
Date registered: Jun 2011
Vehicle: 1994 Mercedes E320
Location: Georgia
Posts: 63
1994 E320 temp issues

I have recently purchased a 1994 E320 with 200000 miles on it, the temp gauge is erratic, the records included with the car show erratic temp readings as far back at 1996 @ 42000 miles. The car appears to run hot at times, I have replaced the viscous fan clutch and thermostat, cleaned the fan, the temp had dropped back to the 80 deg c mark, I have driven the car with the a/c on for 30 highway miles, and 5 city miles, the temp remains constant average ambient temp was 85 deg f. today I have driven the car 10 miles, average ambient temp was 85 deg f, a/c on, the temp gauge is reading from 80 to approx 100 c today. the coolant is not the correct MB orange. My next plan of attack is replace the temp sending unit, flush the cooling system and replace with correct coolant, if this does not work the water pump and or radiator next. Any suggestions. Thanks
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Old 06-28-2011, 05:36 PM   #2 (permalink)
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Date registered: Jun 2009
Vehicle: 1991 300E
Location: Maryland's Eastern Shore
Posts: 601
The W124 Discussion Forum will have the expertise you're looking for. Please search the W124 forum before posting, however, because this topic has been well covered, especially recently.

Basically, your temp is not wildly out of line and likely isn't doing damage. If it remains up around 100C while driving, you may have any one of a number of issues. If the temp goes that high only while in traffic or idling, I think you're more or less fine.

An item that caused me trouble is the viscous fan clutch. A simple test for this is to roll up some newspaper and use it to try to stop the fan from spinning while it sits at idle. If it does, it's bad. The common solution is replacement, but some say they've had good luck simply draining and refilling the fluid in the clutch.

However, don't start throwing parts at this. That can make your car very, very expensive to own. Diagnose first. Also, there are many threads already covering suggested online suppliers of well-priced, quality parts. Most of the possibilities for your troubles have reasonable DIY solutions that are well-discussed in the W124 forum.

Welcome to Benzworld. Good luck with your car. Enjoy it and don't worry about it too much.
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Old 07-02-2011, 04:24 PM   #3 (permalink)
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Date registered: Jun 2011
Vehicle: 1994 Mercedes E320
Location: Georgia
Posts: 63
Have replaced the defective fan clutch, replaced a fuse in the electric cooling fans, replaced thermostat, replaced temp sending units, actual temperature is now running around 180 or so measured on the outside of the thermostat housing with an infrared thermometer, gauge shows over 120 at times, shows 80 at times, I have changed the sending unit. Any suggestions? it is more of an aggravation than a problem at this time, I really dont want to mount an after market temp gauge under the dash.

Thanks for any suggestions.
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Old 07-02-2011, 04:59 PM   #4 (permalink)
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Check the rad hose's, the inner part of the hose may have separated from the outside on the inside causing a blockage.
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Old 07-14-2011, 07:08 AM   #5 (permalink)
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Date registered: Jun 2011
Vehicle: 1994 Mercedes E320
Location: Georgia
Posts: 63
Erratic temp readings

The temp gauge will from time to time peg out over 120C when driving, it may stay there for a few miles, it may peg out on startup in the morning after sitting overnight, the gauge may bounce from 80-90C while driving. when the temp gauge is pegged over 120 if i unplug the sending unit wire the gauge will sometimes go back to normal operation. I have checked the actual temp with a digital infrared thermometer and it is normally between 175 & 185 F. The engine wiring harness was changed a coulple of years ago, the sending unit has been changed, all sensors on the thermostat housing have been replaced with new ones, thermostat has been replaced, cooling system has been flushed, hoses have been checked for defects, viscous fan clutch has been replaced, correct coolant is in use.

Anyone have any suggestions of ideas?'''

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Old 07-29-2011, 09:55 AM   #6 (permalink)
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Date registered: Jan 2005
Vehicle: 1991 300CE, 1992 300CE, 1995 E320, 1998 E320
Location: Southeastern PA
Posts: 18
Install a new Wahler thermostat. Fill the block with coolant via the thermostat housing before installing the new thermostat. Also, fill the radiator with coolant (50/50 mix of MB coolant and water) before reinstalling the upper radiator hose. After running the engine up to operating temperature and cooling down make sure the coolant in the expansion tank is at the full level.
Fred Hoelzle
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Old 07-30-2011, 05:33 AM   #7 (permalink)
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Date registered: Jun 2011
Vehicle: 1994 Mercedes E320
Location: Georgia
Posts: 63
Thanks for all the ideas. However the problem can occur at cold startup, when engine has not been run for several days. when the gauge pegs or shoots over temp I can unplug it, this seems to reset the gauge and it again works correctly.
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