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.

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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/