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!

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.

__________________
Regards . . . . JimF
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'94 S500 Cpe

Visit my Mercedes Web Page

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.

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

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

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