w140 overheating
 

W140 s500 coupe, has begun to overheat. Normally it temps at approx 80-90 but now goes into 110+. I believe the thermostat operates at approx 80 c, vicous fan at approx 100 c and aux fans beyond that. Both aux fans are operating. I have replaced rad cap as it looked worn but problem is still there. Considering the car previously never reached 100 i'm suspecting the thermostat. Advice required before i cook the engine!

the Tstat sounds. . .
 

like it's a good place to start. Sounds like it's stuck partially open.

Also check your af/w ratio: I firmly believe in a 40/60% ratio (af/w) and use Mercedes AF and distilled water. If it's 'dirty' this might be a good time to thoroughly flush it and refill with fresh AF and distilled water.

One of my Cool Harness will help also after the above is done.

Thanks for the reply Jim.
Do you know if the thermostat is located below the top housing held on by 3-off allen headed bolts or to the side of the housing held on by 3-off hex headed bolts. Thanks.

The Tstat is located
 

in the worst position: on the side next to the little hose! It comes off easily but is a knuckle buster to put back.

Thanks Jim, replaced the thermostat today and the car runs normal again.
Not much skin left on my knuckles though!