Why would my temperature run hotter after a new water pump was installed?

I just had my water pump replaced by my local Mercedes dealer. They also changed the hoses and the serpentine belt. While they were at it, they flushed the entire system and of course they refilled it with all Mercedes liquids.

On the way home, I noticed that my car is running 5 or 10 degrees warmer. I’m sure you guys know that the actual temperature is only indicated at 80 and 120 and that there is just a mark in between that I think is 100 degrees. My car always ran just above 80. I would say it was 85 degrees, except on very hot days or when sitting in traffic after running long and hard, when the temperature would creep up toward 100 and the fans would kick in to bring it down. Now my car runs closer to the 100 mark than to the 80 mark. I would say it is running at 95 and sometimes a little lower in the middle of the marks at about 90.

Why would my temperature run hotter after a new water pump was installed?

I am sure that more heat cannot be a good thing. For example, my oil pressure usually was lower when my car ran hotter on hot days in the past and sure enough, my pressure was slightly lower yesterday. They also changed the oil and filter and I suppose they may use slightly different weight oil for the summer, although I did not make any such request. My car is always maintained at the dealer and I have been faithful about changing the oil in between every scheduled 7500-mile check-up. My oil is always a nice golden color. It has never been black.

__________________
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/

Did they intall a new thermostat?

The high speed fans come on at 105-107 C. The thermostat start opening around 87-90 C. The new thermostat maybe opening a little bit later than the previous one.

The temperature in my 94 E320 started to stay a little below 80 C on cold mornings, replaced the thermostat and now it is always above 80 C and gets close to 100 C in city traffic.

You maybe able to lower the temperature by turning on the AC, as the pressure on the system turns on the fans at low speed regardless of coolant temperature.

According to MB, temperature approaching 120 C are normal in certain load conditons.




"Air Conditioning - During periods of extreme engine load (climbing hills or towing) along with high temperatures, use of the A/C may exceed the capacity of the cooling system.

Cooling - High Coolant Temperatures

MD-NET ADMINISTRATIVE MESSAGE

DATE: JULY 22, 1994

MESSAGE #: 322

TO: ALL DEALER SERVICE MANAGERS / ALL DEALER PARTS MANAGERS

SUBJECT: GROUP 20 - ALL MODELS, COOLANT TEMPERATURES


The coolant temperature of MB vehicles may rise substantially above 100°C/212°F at high ambient temperatures while the vehicle is:

a) stopped
b) in city traffic ("stop and go")
c) when driving uphill
d) when driving at very high speed, i.e. with high engine load


Engine coolant temperature returns to "normal" upon returning to regular driving conditions. In individual cases, the temperature reading may approach the red field of the temperature gauge.

Provided the cooling system is well maintained and in good working order, such temperature levels do not create any danger for the engine and, therefore, give no cause for concern. The boiling point of the recommended coolant mixture (Refer to Service Information 20/9 and Service Microfiche group 20), is much higher than 1OO°C."

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Zafar
94 E320 58000 Miles

I did get a new thermostat and it sounds like my car is doing the same thing your car did. I guess my old thermostat was just not working very well, but I think I like the idea of running a little cooler. My car has not reached 100, so I guess I am in the safe operating temperature range. I just liked it better when it was a little cooler.

Thank you for your information. It makes me feel a little better knowing that it is probably normal, although I still wish it were 5 degrees cooler.

Thanks again for your reply

__________________
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/

I think the temperatures referenced here are Celsius, not Farenheit.

This happened to me. I used to be at dead 80 most of the time, a little higher for a bit after coming off a highway. Changed water pump, hoses, belts (belts tightened exactly with a Krickit); was green antifreeze now correct mix of MB antifreeze. Now I see 85-87. I'm quite certain that I don't have an air pocket.

Two things:

1. I don't know the tolerances that thermostats are built to; my first one was a Behr, this one is a Wahler (sp?). My readings would fall into 5-10% tolerance. And who knows if the dash gauge is exact in the first place?

2. I also got a new pressure cap for the overflow tank. It was very tight, and in the process of changing it the neck weakened and now bubbles and leaks (new one arrives Tuesday). This amounts to a pressure leak (not a lot, but it is something), and this will cause temps to go up. I'm not driving on any significant trip until this is replaced, and I'm watching temps like a hawk.

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86 560SL
With homebrew first gear start!
85 380SL
Daily Driver Project

http://juliepalooza.8m.com/sl/mercedes.htm

Don't forget, these thermostats can be had in 79C Degrees or 87C Degrees varieties.

__________________
2012 E350
2006 Callaway SC560

I thought the thermostat temperature rating had more to do with the holding the water in the block during the initial heat-up of the motor and how soon the heater would work on a very cold day. I didn’t think the thermostat had all that much to do with normal operating temperatures. It is hard to believe that the thermostat would be closed all of the time during normal operation.

Would a lower temperature thermostat really maintain a continuously lower operating temperature? If it would, then why would anyone want a hotter motor? My way of thinking is that more heat must be a bad thing for things like my gaskets, wiring harness, oil life, and overall engine life.

I am definitely going to ask about getting a lower temperature thermostat, if it would reduce the normal operating temperature of my car.

__________________
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/

Yes, the temperature are in Celsius, not Farenheit.

ksing44,

You can do some modifications to turn on the high speed fans at a lower temperature. If you do a search under "cool harness", you will find many threads. You can make one or JimF sells them on his webiste item#18.
http://pages.prodigy.net/jforgione/MB_S500.html

__________________
Zafar
94 E320 58000 Miles

There's probably a difference in the thermostat. The come in different degree ranges as mentioned above. It's stamped on the old and new one. Another possibility is that there's a bubble in the system that was not bled out and this will yield higher temps 8-10 degrees C. To get rid of the bubbles, park the car front up a hill or curb while warm and open the bleeder screws a little. If there are bubbles that come out, you will have fixed the problem.
Steve

Why do a lot of mercedes owners confuse the 2 different heat scales? I have farenheit readings n my ol 450 sl 1977. Running temp is from 180 to 200 degrees FARENHEIT !! Running at 100 CENTIGRADE is fine!! (what does this equal in farenheit>), When mentioning temps state either or! Abe G

My car is a US version and it reads Fahrenheit for the outside temperature readings, but the engine temperature is Celsius. I am not confused about the two different temperatures. As a frame of reference, I always think about the boiling point for water, which is 100 degrees Celsius and 212 degrees Fahrenheit.


Here are some formulas for making conversions and a link to a converter.

http://www.csgnetwork.com/tempconvjava.html

Tc = temperature in degrees Celsius, Tf = temperature in degrees Fahrenheit

/ represents division, * represents multiplication, - subtraction, + addition and = is equal.

Tc = (5/9)*(Tf-32)

Tf = (9/5)*Tc+32

__________________
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/

maybe too simple..

Take it back and ask them to bleed the air out of the coolant system again. Tell them it's running hotter than before...


Michael

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Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E

I would run the car with the heat on high while driving and watch the temp gauge drop.

Then I would idle the car from cold for five or ten minutes with the pressure cap off to bleed the system.

Also remember that a car running too cool is inefficient.
Always cool to compare gas mileage with the higher operating temperature then compare to previous running temp.

Running the car with the cap off won't bleed the system. You need to use the bleed screws.