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Howdy: I purchased my 1991 3 liter 300E in 1995, it's always run a little warm and hot to hotter in the summers.
The last several years the temp has ticked up a couple notches at a time, every year seems to run hotter & hotter. When the outside temp is 50 degrees F after driving around town or freeway, come home and idle for 5 to 8 or 10 minutes the eng. temp will climb to just over 100 C. the crazy thing is I've replaced all cooling components with BRAND NEW O.E.M. parts, radiator (2X) fan clutch (2X) water pump, hoses, thermostat more times than I can remember, The big huge resistor that controls low-speed of auxillary fans and on and on ad infinitum. The car had a valve job at 100K miles! The AC radiator which sits in front of the engine radiator has been pressure back washed to remove bugs and dirt. The aux. electric fans kick in at the correct temp. and the AC system pressure has been check and rechecked with Freon added to kick the fans in a little early. NOTHING BUT NOTHING BUT NOTHING HAS HELPED. The really odd thing is, go out on the freeway and within a few miles the temp will drop below 80 F. even a on hot summer day with the AC on.
SO, do you have an answer? Sure would appreciate some help as I'm really stumped here. Thank you
Zarcov
 

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1987 260E Mercedes
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154 Posts
Hey, I understand your concern. I have a similar issue. Any help would be appreciated!!!
 

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1994 E320
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1,730 Posts
Well, I'd hate to shock you, but the way your car is behaving sounds perfectly normal to me.
My car does the exact same thing. When it runs idle for a few minutes or when I'm in heavy stop&go traffic, the temp climbs to the neighborhood of 100-110 (near and beyond the lone notch between 80 and 120.) As soon as I drive on, it drops right down to 80 (and even below that when I had the 65C thermostat.) By the time the car warms up to 80, the engine fan is engaged (you can actually hear it roaring.) The auxiliary fan doesn't start running at high speed until the temp hits 115, and after that it cools right down to 90, when it reverts back to low speed (with the AC on, disconnects when AC is off.) And I live in Saudi Arabia!!! I've never had any problems with the car. So I wouldn't lose any sleep over it. (But that's my opinion, and I could be wrong.)

Shady
 

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I also think its close to normal. But I would rev it with the radiator cap off to purge the system of air and double check that you are running a godd 50/50 mix of coolant and water.
 

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mercedes 350sdl, 2005 ML350, 1991 300E 2.6 to 3.0, 1988 300E
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165 Posts
also check your windshield washer heater, the unit is heated by coolant and is known to crack, i replaced my radiator thinking it had a leak but my cooland was ending up on the winshield washer bottle. the heater is located inside the winshield washer tank.
 

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'96 sl500, 87 300td
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134 Posts
Sounds about normal for a gas engine. My 124 is a 300td but my sl500 does the same things with the temp.
 

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Chevy Monte Carlo SS
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I had the same issues with my 300E. I replaced all the parts you did, even the coolant temperature sensors. I still had the car running warm. I hear its normal, but I did not like the fact that the temp went that high. After exhausting my funds tracking down the culprit to the warm running condition, I sold the car. The new owner also has a W124 that does the same thing. He said it is normal for a car that old, and the car has not overheated once, even in stop-and-go traffic. I say, flush the coolant,bleed the system of air, and if that doesn't work, sell it!
 

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Depends on the day!
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From what I have seen this is quite normal. Friend of mine Completely rebuilt his 300SE, still regularly tops 100+. Everything in that car is genuine MB..
His car did the same thing prior to the rebuild. M103's just like to run hot.
Oh, he now has 250K on the motor w/o warping or excess wear etc, etc..


Jonathan
 

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92-93 MB E320
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i have corrected/change everything listed but still overheating with average 90-100c

1. radiator hose leaks
2. cracked windshield heater tube
3. plugged heater hose
4. coolant temperature sensor
5. coolant temp fan switch
6. relayed the fans to increase voltage
7. reconditioned the viscous fan clutch

but finally the culprit was the ac filter pressure switch. the electric fans should switch on when AC compressor is working. i corrected it temporarily by using the compressor power to switch it on until i can finally replace my filter drier which is defective despite its 6 months old.

my temperature now ranges from 80-85c

1 almost have replaced my water pump because of this long battle with overheating

hope this helps
 

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92-93 MB E320
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21 Posts
i have corrected/change everything listed but still overheating with average 90-100c

1. radiator hose leaks
2. cracked windshield heater tube
3. plugged heater hose
4. coolant temperature sensor
5. coolant temp fan switch
6. relayed the fans to increase voltage
7. reconditioned the viscous fan clutch

but finally the culprit was the ac filter pressure switch. the electric fans should switch on when AC compressor is working. i corrected it temporarily by using the compressor power to switch it on until i can finally replace my filter drier which is defective despite its 6 months old.

my temperature now ranges from 80-85c

1 almost have replaced my water pump because of this long battle with overheating

hope this helps
 

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1987 260E Mercedes
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154 Posts
The only reason why I asked was due to the fact that I warped a cylinder head about 6 months ago from my car somehow overheating... [:(]
 

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How is the condition of your car now on the overheating ? I have the same problem. In my case I've changed most of the things as mentioned by the other members but the problem of overheating stays.
Is by changing the ac filter pressure switch really work.
 

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1995 E320 86 16v
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71 Posts
had a 95 E320 and does the same thing. There's an article on the current STAR magazine that discuss a "hot running 400E", they did a mod on the fan clutch to cure the problem.
 

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Chevy Monte Carlo SS
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189 Posts
I think it's a problem. With the added heat, the engine parts are under more stress. The engine oil becomes less viscous, and coolant temps rise . When my car ran "warm" in traffic (100C), it would begin to idle really rough, and the horn would become really weak. I lost my first motor on my 300E due to the "warm" running condition. The car never overheated, but the constant heat ended up warping the cylinder head. It was, bye bye gasket and hello new motor. The sad part is I always paid attention to the temp, and the motor still blew. I replaced the motor with another one, and all was great for about 1 1/2 years. The car then started to develop the same problem, temperature was high, but not overheating. I replaced all the "usual" parts, and more, yet the problem continued. I went to very reputable MB shops and got the same reason every time, " These cars are supposed to run like that" or "It's an old car, what do you expect?". I was tired of hearing those excuses, and was not about to lose another motor. The W124 had to go, so I sold it. I guess it's a textbook situation, you love something, but you still had to get rid of it.

Some call it quitting, some call it giving up, but I call it, a new beginning. I love my Monte Carlo [:)]
 

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'89 260E
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18 Posts
over heating is a problem...

I once drove a W124 230E in Malaysia (tropical humid climate) and in the middle of the day, the car stalled and engine cut off. I sat in the car for 5 mins while it cooled down, then started it up again and it was fine. [:I]
 

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My 300E does this also. I live in Fl and it didn't used to do this. I could leave it a idle or in traffic for an hour. Now I have to turn on the heater when the outside temp gets above 95. I have replaced all the above and more. I decided it was a blocked engine and lived with it another year. I replaced the engine and still the same!
From 90 outside air down I must turn off the AC when I stop at lights. I'm changing the AC now hoping to fix it once and for all.
 

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89 300E 195000
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124 Posts
you can drive a 300E even when the temp in almost in the red... it will not hurt it. dont believe me? call mercedes in germany... stuggart i think it is. they will tell you what i have told you. they make the things so tough that they dont break from overuse they break from years of overuse.
believe it or not but for the earlier year benzs (pre 95) this is totally accepted. i would be concerned about the newer ones only because chrysler is now involved and too much bean counting.
 

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89 300E 195000
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and if you dont believe me... just look at where shady lives... think it gets hot over there? and i bet his car laughs at the heat.
 
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