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  #1  
Old 06-19-2005, 07:42 AM
ksing44's Avatar
1995 E320 SE
 
Join Date: May 2002
Location: Downingtown, PA
Posts: 658
Car runs hotter with new thermostst and water pump?

I have a 1995 E320. My car always ran at about 85 degrees Celsius, but now it runs at about 95 degrees Celsius after installing a new water pump and thermostat. The dealer also flushed my system and replaced the hoses when they replaced the water pump and thermostat. I don't like the fact that they "fixed" my car and now it runs HOTTER!

What can I do?

Why would it run hotter?

Is there an 83 degree Celsius thermostat for my W124? The dealer told me that only an 87 is available.

Do you think I should just try another 87 degree thermostat? Could it be that the thermostat is just a bit faulty?

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I just couldn't give up on my 1995 E320.

I think it might be like always going back to that same bad relationship with an ex girlfriend.
You feel you love them too much, or you are just too stupid to know any better.



Flickr slideshow of my 1995 E320
http://www.flickr.com/photos/24145497@N06/sets/72157616572140057/
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  #2  
Old 06-19-2005, 11:33 AM
Ali Al-Chalabi's Avatar
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Sounds like it is probably functioning normally now. It should run around 90 on the highway and 90-100 or higher in traffic. After the thermostat starts to get old, it starts to open at a lower temperature. That is why a new thermostat makes the car run warmer.

An 87C Mercedes thermostat starts to open at 87C +/- 2C. It is only fully open at and above 102C. That means it will restrict coolant flow through the radiator at any temp below 102C.

Looks to me like they did fix it properly.
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  #3  
Old 06-19-2005, 11:50 AM
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Quote:
Originally Posted by Ali Al-Chalabi
Sounds like it is probably functioning normally now. It should run around 90 on the highway and 90-100 or higher in traffic. After the thermostat starts to get old, it starts to open at a lower temperature. That is why a new thermostat makes the car run warmer.

An 87C Mercedes thermostat starts to open at 87C +/- 2C. It is only fully open at and above 102C. That means it will restrict coolant flow through the radiator at any temp below 102C.

Looks to me like they did fix it properly.

I agree.. Now back up to normal temps..
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  #4  
Old 06-19-2005, 02:04 PM
ILUVMILS's Avatar
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As a precaution you may want to check the fuse for the low speed auxiliary fan. The low speed fan runs when the high side A/C pressure reaches about 300-350 PSI. I see a lot of these fuses blown at the beginning of the A/C season. This will definitely cause the coolant temperature to rise, but it's more noticable when idling for extended periods.
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  #5  
Old 06-19-2005, 11:15 PM
Strife's Avatar
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Same thing happened to me. I was running 80 in summer and 70 in winter. Changed the water pump and thermostat, new MB fluid and went to 85-95 all the time. I played with the old thermostat in some hot water and determined that the old thermostat always stayed stuck open a little.

This is a "better" failure mode than locking shut (like my GM cars seemed to do)!!
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  #6  
Old 06-20-2005, 04:14 AM
ksing44's Avatar
1995 E320 SE
 
Join Date: May 2002
Location: Downingtown, PA
Posts: 658
You guys are HOT!

Quote:
Originally Posted by Ali Al-Chalabi
Sounds like it is probably functioning normally now. It should run around 90 on the highway and 90-100 or higher in traffic. After the thermostat starts to get old, it starts to open at a lower temperature. That is why a new thermostat makes the car run warmer.

An 87C Mercedes thermostat starts to open at 87C +/- 2C. It is only fully open at and above 102C. That means it will restrict coolant flow through the radiator at any temp below 102C.

Looks to me like they did fix it properly.
Thank you Ali Al-Chalabi and the others that echoed his view. I do feel better knowing everything is as it should be, although I still like the idea of it being a bit cooler. Maybe next time I won't change the thermostat.
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I just couldn't give up on my 1995 E320.

I think it might be like always going back to that same bad relationship with an ex girlfriend.
You feel you love them too much, or you are just too stupid to know any better.



Flickr slideshow of my 1995 E320
http://www.flickr.com/photos/24145497@N06/sets/72157616572140057/
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  #7  
Old 06-20-2005, 11:09 AM
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My thermostat failed in the closed position leading to overheating and to what I believe the final weakening resulting in head gasket failure.

The car ran on the cool side. This was my first Mercedes and I thought this was a good thing. In trying to diagnose a front end problem, when my indie was driving the car around he remarked that the car was running "a little cool".

The car used to run 80-90, now mostly 85-95.

glenmore
1991 300CE
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  #8  
Old 06-20-2005, 11:15 AM
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300e runs at 87 degrees with new coolant, Red Line Water Wetter, and thermostat

300ce runs at about 82 degrees with new coolant. I am more comfortable with it running at 82 degrees...

Both elevate a bit at red lights, warmer ambient temps and a/c running....

They never get anywhere near 95, however.
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  #9  
Old 06-20-2005, 01:19 PM
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As an added bonus: You'll likely notice an increase in your fuel economy now that your engine is running at the proper temperature.

Jeff Pierce
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  #10  
Old 06-20-2005, 01:46 PM
ksing44's Avatar
1995 E320 SE
 
Join Date: May 2002
Location: Downingtown, PA
Posts: 658
Some like it HOT!

OK, I guess I will try to learn to love my new higher operating temperature and I won’t even think about keeping an older thermostat that keeps me cool.

Thank you everyone
__________________
I just couldn't give up on my 1995 E320.

I think it might be like always going back to that same bad relationship with an ex girlfriend.
You feel you love them too much, or you are just too stupid to know any better.



Flickr slideshow of my 1995 E320
http://www.flickr.com/photos/24145497@N06/sets/72157616572140057/
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  #11  
Old 07-02-2005, 09:54 PM
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Location: Urbana, Missouri
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thermostat

A 300SD I have ran at 67 to 70 degrees. Installed new thermostat and it's been running at about 90 ever since.
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  #12  
Old 07-03-2005, 02:46 PM
Ali Al-Chalabi's Avatar
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Location: Knoxville, TN
Posts: 1,837
Cooler is not necessarily better. Mercedes designs there cars to run at a certain temperature for a reason. If they wanted the car to run at 80C and cooler, they would have put an 80C or cooler thermostat in the car.

On my car, whenever it starts running at 82C or less, I change the thermostat.
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  #13  
Old 07-03-2005, 03:08 PM
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Although what you describe is normal, you may want to check your Antifreeze/Water Ratio. If more than 40% Antifreeze than your car will run hotter. Antifreeze does not dissipate heat as well as water does.

Phil
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  #14  
Old 07-03-2005, 03:19 PM
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Most OEs (and DB is in this group) specify a 50 percent mix of antifreeze to maintain maximum corrosion protection, but usually specify no more than 70 percent. Only above 70 percent (assuming the cooling system is in good working order) should one expect to have problems due to the lower heat capacity of the coolant as the antifreeze concentration is increased.

Forty percent antifreeze is below spec.

Duke
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  #15  
Old 07-03-2005, 04:36 PM
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Quote:
Originally Posted by Ali Al-Chalabi
Sounds like it is probably functioning normally now. It should run around 90 on the highway and 90-100 or higher in traffic. After the thermostat starts to get old, it starts to open at a lower temperature. That is why a new thermostat makes the car run warmer.

An 87C Mercedes thermostat starts to open at 87C +/- 2C. It is only fully open at and above 102C. That means it will restrict coolant flow through the radiator at any temp below 102C.

Looks to me like they did fix it properly.
Do NOT agree ...Gets old and open at lower temp? what kind of talk is that?
Do you know how the termostat works? There is a gap of at least 20F betweem open and close and it shouldn't matter in this case.
Why do you people mislead ???If the radiator is good the engine should keep the 85-90 ...

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