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97 E320 normal running temp???

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Hello. I am new to Mercedes and have a question about what the normal running temp should be. I have had the car a couple weeks now and have been attempting to fix some small surface rust spots before I set it loose. Today while working on it I let it run awhile and I noticed it was consistently just under 100 C (maybe 97-98 C) in 70F weather. This is also the temp that it was at the whole way bringing it home from Chicago with no issues. Is this normal? Also there was a slight antifreeze smell today while it was running, but everything looked normal...temp was steady at just under 100 C and there was no AF leaking out anywhere. Thank you for your help...

Indydad
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'96 E320 sedan
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77 Posts
Mine runs at about 85 deg C in normal running. A little higher in warmer ambient temps and a little lower if it is cool and raining.

I suspect your thermostat is not opening all the way and limiting flow through the radiator. That or fans are not running as/when they should or you might just be due for a coolant flush.

As witness the above, you probably have some research to do. I'd start with a coolant flush and go from there.
 

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2002 E430 4-Matic
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1,339 Posts
About 85c for me as well with the E430. Neither of our w210s ever got near 100c unless stuck in heavy hot summer traffic. I doubt the trouble is with the electric fans as they shouldn't be running in the winter anyway. Plus, you run at the same temperature whether on the road or just idling.
My first guess would be thermostat too.
 

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97' E320
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24 Posts
Discussion Starter · #4 ·
Thanks Figuero...Should I do this right away or can it wait a couple of weeks since it is not getting any hotter than 97C? I am kind of running into many maint. things(oil change, ATF change, brakes, spark plugs) at once on it right now and don't have much free time. Do you know how much a Indy or MB shop would charge to do this?
 

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2002 E430 4-Matic
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1,339 Posts
Kajtek1 - Why do you suspect the fan switch? He is running 97c in a midwest winter on the highway?

I've never done a MB diy thermostat, can the old fashion test of suspending it in a sauce pan with a good instant read thermometer work?
 

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1997 E320, 1997 S320
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2,951 Posts
m104 runs a little hotter than m112 in my opinion, so i think the running temperature of your car is ok. mine always runs above 90, and it has passed the 100 mark a couple times when i have been stuck in really heavy traffic for a long time, i just open the windows and turn the heat on high for a few seconds and it comes down. the electric fans don't kick in until it reaches 107 i think, so you probably won't hear them since yours hasn't passed 100. there is a way to test the electric fans from the ac controls, but can't remember it.
you car is probably fine to drive, i would worry about this after you have finished what you had planned to do. then in a couple of weeks or a month, i would change the thermostat since it is so cheap and easy, and also i would drain all the old coolant out and replace it. mb recomends replacing it every 3 years i think. coolant is really cheap. but get the mb coolant or zerex g05 which states in the back that is mb compatible. use 50/50 mixture.
 

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03 E320 4M Wagon & 97 E320
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Figuero and tirona offered some sound advice.

If the thermostat has been there for a while, that is the cheapest place to start. The M104 thermostat is cheaper than the rest of the W210 engines and it takes only a few minutes to change and you won't lose much coolant because it is on the top.

The electric fan should not be a factor now because it is mainly for the AC condenser.

However, the temp sensor/sendor could be an issue so Kajtek1's advice to check with thermometer is a good one.

I would just replace the thermostat first.
 

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1922 Ford T no OBD, no ECU, no SCN
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37,920 Posts
Is it cheaper and easier to replace the thermostat, than buy the $9 thermometer and do 20 second testing?
Engine getting hot on parking, while operating OK at the highway is indication of fan not working. All our MB open thermostats at about 75C and when fully warm operate at around 85C. I had my E320 parked on 110F desert with AC at full blast and it never even got close to 100C.
 

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03 E320 4M Wagon & 97 E320
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The T-stat for his car is only $14. The electric fan should not come on at that temperature. If it is the electric fan related, the more common problem is that thin belt connecting the two fans but they should not matter at such a low temperature.

The viscous fan clutch is another possibility but it does a partial coupling around 92 to 100 deg C and a full coupling above 115 deg C.

Another possibility could be the recovery tank cap. It might not seal perfectly since you mentioned you smell some coolant.

These T-stats do wear (spring gets less elastic) so it is a cheap thing to replace. Normally, the signs of a "tired" T-stat is at both ends, i.e., not be able to close 100% and not be able to open 100%. So how fast does the temp go to 100 deg C? If it takes a while, then it is another sign of a T-stat problem.
 

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97' E320
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Discussion Starter · #13 ·
It warms up fairly quickly and it is setting in the garage now, I haven't started driving it everyday yet but I can go out and let it run to see how it does. I ordered the thermostat last night and should have it a few days. If this doesn't do anything I will flush the coolant. So from what most of you are saying, you don't think it is a fan issue? thanks.
 
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