I'm new to mercedes. When I bought the car the expansion tank was crack. The car was heating up but not overheating. I bought it were the climate Is not too hot probably 80 degrees Fahrenheit. I live in las vegas were is on average in summer time 100 degrees Fahrenheit. When took it to the Mercedes benz especialist they replace the expansion tank, they also installed a thermostat that is supposed to make it run cooler. He noticed the fan shroud was missing he order it and installed it. The car still running hot. If im constantly going it stays righ around 100. but if i'm in stop and go traffic it climbs up to 110 - 115. They told me It could be the radiator, and that it looks that the car has a nissen radiator wich is aftermarket. Does anyone know what it could be? Should I just replace the Radiator? Any suggestions. by the way my car is the w140 body style.
Thank you.

 

check if the auxilliary fan is working well.

check if the viscous fan clutch is working well.

open the expansion tank (slowly) and see if there is bubble coming up once in a while (cylinder head leak).

feel for hot-spot on radiator (operating temp...engine off).

 

if the radiator has a cold spot in the middle of it then you must replaced the radiator. if it dosent i would look at the viscous fan clutch if its not locking up thats your problem the fan locks up at like 107 i think you can tell if its not locking up by get the car upto like 115 shut off the motor and run out and check if the fan spins freely it dosent that you got a bad fan clutch. but do check for bubbles or even sluge on your radiator cap thats classic signs of a blown head gasket. ps fix this before you fix your ac. lol

 

no bubles or slush on cap or water on oil. the fan seems to be hitting the shroud. so its not spinning freely I will get the motor mounts replaced and see if by the fan spining freely it helps it out. Thank you I will let you know what happens.

 

hi, new to benz also and I have a 1995 s420 with the same problem you have as in the same, and also I am in las vegas. Pls help me out if you were able to solve the problem. my personnal e mail is antdaban@yahoo.com Thank you very much

 

I live in SLC and have a 94 S500 that tends to run on the hot side. I've been worried about it overheating and tend to stare at the temp guage more than my speedometer. When climbing hills on hot days I would be forced to turn off the AC. Don't take this as a shameless plug but last week I purchased a new cooling harness from Jim Forgione. http://pages.prodigy.net/jforgione/MB_S500.html It took seconds to install and turns the auxilary fans on at 92 degrees. You might need to test your fans. They should come on around 100 degrees with the AC on. I climbed the same hill today with 97 degree outside temps and stayed below 100 on my temp guage. Driving around town and in slow traffic is cake-walk now. Hope that helps. It did for me.