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Discussion Starter #1
Hello:

I'm a complete newbie and got a 1993 W124 E220 recently. I made the mistake of presuming everything worked properly (by the look of it) and took it on the road several times following the purchase. The car was a bit shy of 110000km. The previous owner was elderly and didn't drive much. The car was garaged and looked clean inside the engine bay, with oil and coolant both looking good, hence the presumption.

I did not know how to read the temperature gauge correctly, but I did notice that the thermometer would go above the unmarked bar above 80C. I checked the owner's manual and it doesn't really say what temperature it is. (is that mark 100C?) It goes above that bar a bit but below 120 when I drove it for a while and then stops for traffic, or parked for a while. Engine also has a slight pinging noise when it goes above that bar which I didn't think was related, but was suspecting some carbon build up due to lack of driving.

However, several days ago, when it got pretty hot outside (32C), with AC on, the AC suddenly didn't feel very cold. I did notice the gauge to go a bit higher like usual, especially after parking. I then drove on a freeway (but not a fast one, with a bit of traffic it's like 80km/h tops), and when I coasted off of it and took a look at the first light, I was shocked to see the needle at/above 120. By then I was trying to move forward to the next area where I can stop (no shoulder), and any acceleration would result in engine pinging. It took me about another two minutes? to coast about 150m to a stop.

I shut off the engine but left it on acc. was expecting steams everywhere, but when I opened the hood, the steam was coming off the little vent tube on the auxiliary tank. The electrically motorized fan in the front was going full blast. There's also a faint metallic smell, like wires burning, or brake pads overheating. Any idea what that might be?

The aux tank still had some fluid in it while it was steaming, but as the car cooled down (it went down to a little above that unmarked bar in about 5 minutes), all the fluid in the tank disappeared. I had to add about 3 liters of tap water just to get it back to the same level in order to go to the next shop, which it did fine.

The mechanic immediately identified the fan fluid clutch as the problem and was replaced by a german made behr. The fan felt much stronger than I first saw (something an experienced owner/mech would probably have identified immediately). He also topped off coolant levels with some antifreeze. The AC refrigerant was also a bit low and that was vacuumed out and replaced.

I drove it a bit afterwards, and the temp gauge would read only a bit above 80 and rise only a bit higher in city traffic, but never above that unmarked bar. The pinging is mostly gone but still occurs in some rare circumstances under pressure (used to be able to produce it easily after warm, but not sure how to reliably get the noise now). AC is cold. Everything seems fine for now.

However, I can't help but feel worried. I know that overheating might cause some unseen issues down the road, including head gasket leaks. That and the mysterious metallic smell. Would the coolant vaporize over time when it overheats (presumably above that unmarked bar?)? After the temp gauge hit 120, should I be concerned about repercussions? What should I watch for, and maybe repair/inspect preemptively?

Any comments or suggestions are much appreciated. Thanks in advance.
 

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W124
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The smell of coolant being pushed out of the overflow tank is a sweet smell so I don't think that is what you detected. Its hard to say what could have caused that metallic smell. I don't hink the car being run at that temperature for a short period is an issue but only time will tell because you really don't know if the previous owner had experiences like that. I would look into the history of the car to see when the radiator was last changed. If you can't tell and it looks original, you need to get that out of there next and change the thermostat at the same time.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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Also, anytime your coolant temperature goes near/ past 120*C put on your heater on full blast at the highest temperature it can get and coast to a stop. Safely.
^This and DO NOT turn off the engine. The water pump needs to continue turning to draw away the heat inside the block.
 

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1995 E320
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^This and DO NOT turn off the engine. The water pump needs to continue turning to draw away the heat inside the block.
Unless, like me, you've lost your serpentine belt because of a seized whatever it was. Waterpump wasn't in effect.
So ascertain the cause immediately after stopping.

I believe there is a tiny little electric pump that circulates water through the windshield washer bottle. Doesn't pump enough to cool a running engine though.
 

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1995 E320
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Which reminds me; changed the transmission oil in my car and the shifting issues seem to have disappeared.

However, I left my car running/ idling last night, for a good 20 minutes and the coolant temp went above 100*F, but not hot enough to activate the aux fans. I was checking my transmission oil levels and the dipstick was burning hot. In the back of my mind I thought it was running a little hot, so I let it run outside (The garage at home is the only flat place to work, the street is inclined.)

I guess a radiator flush is in my future now.
 

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1993 300e 2.8
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Metallic smell could be a caliper hanging up. Inspect all four corners for free rotation. Unless she had it regularly serviced (with records) change all fluids.
 

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Discussion Starter #9 (Edited)
thanks for all the advice! i'm a bit worried now that I turned off the engine right after stop. it was intuitive as i was coasting slowly yet the car was still hot. the coolant level was low as I poured 3 liters of water into it before driving off, and afterwards the shop poured another 2L of coolant concentrate into the tank without having removed/drained anything. I am going to do another coolant flush when I get a chance, because the way it was done felt a bit weird.

Noted about the heater. Will try to keep calm and turn it on if the car overheats, though I hope it'll never happen again.

After seeing the post about transmission shifting, I failed to mention that when the car was hot, the transmission would not upshift (after 2nd? or 3rd? i wasn't sure). It did occur before, and I wonder if it's got something to do with overheated radiator, as the ATF also cools with it? Most of the time it shifts fine though, but even after coolant replacement there was once or twice where it seems to upshift a bit slowly, though not as bad as when it was overheating (where it simply refused to upshift). I'll have ATF replaced with something with MB approval. Any recommended ATF fluids?

RE: the metallic smell. The car was actually well kept with new pads and rotor. No seizing detected, and the car was driven gently and pretty much coasted most of the time including on the highway. I wish it was the brakes, though it does seem unlikely?

I cannot tell if the radiator is original (how do you tell? the fins do look really clean from the inside), though the fluid had been changed, with what looked like green/blueish coolant similar to original MB spec. All fluids looked okay, with surprisingly new differential fluid. I am going to replace atf, differential, & coolant, along with fuel filter to see if that helps with the slight pinging that sometimes occurs at very light throttle around 1500rpm (not sure why, probably fuel starvation? any ideas?)

I'm keeping my fingers crossed that the head gasket wasn't damaged due to this incident.

Thanks again for your comments. I appreciate them.
 

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Current, 90 300CE, 92 400E (Sold 95 E320,70 250C, 91 190 2.6, 91 420 SEL, 95 300D, 87 TD)
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If you don't know the condition of the radiator.... They're relatively inexpensive and super easy to replace.
 
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