Hi Tim:

Oh...sounds so familiar. I struggled for a year, finally fixed the problem. I should have listened to Hatty and Brian and would have saved a year of stress!

Anyways, first thing I did when I had the problem was check for coolant levels. If it was dropping, I understand it indicated a possible leak and therefore, a potential water pump problem. My coolant level only dropped when it BOILED!

So, I changed the thermostat. You can tell how well the thermostat is working by watching the engine temperature. You'll see it rise above 80 degrees, spike and then drop. If it doesn't spike fast, I think that it could be the thermostat as it has a problem opening and allowing the coolant to freely flow.

This didn't help me.

Next, I was worried as I didn't think the Aux. fan, (in front of the engine) was kicking in when it got too hot and there wasn't enough air flowing past the radiator. So, I changed the Aux. fan switch. (this was easily a DIY project.)

This didn't help me.

Finally, we examined the radiator. It was changed by MB a few years ago, so I assumed that it was ok. Well, when we examined it found that at operating temperature, only 1/4 of the rad was warm the rest was "ice cold." This indicated a flow problem so I changed the rad.

Problem solved. It was hot today and yesterday and the temp didn't rise much past 80 degrees.

In your case, check to see if the Aux. Fan is kicking in when the engine temp rises above 100. My understanding is that the switch recognizes that the coolant is too hot and the fan kicks in. If the Aux Fan doesn't kick in, try replacing the switch. (Easy and relatively inexpensive.)

I look forward to seeing how you make out.

Good luck, and listen to these guys...they know their stuff....

Brad.

__________________
Dr. Brad

2003 C320 4Matic Station Wagon
2002 C240 Elegance
1982 380 SEL Star Certified