Q&A

 Master

Outside temperatures of 47 C is 116 F that puts pressure on the cooling system but they are designed to run at these temperatures. The cooling system has a thermostat that regulates the engine running temperature I would replace the thermostat (if a lower temperature thermostat is available use that one). Engine running at 120 C ( 248 F) is too high. I will send you an article I wrote about cooling systems perhaps it may help. You must get this checked out and repaired or serious and expensive repairs may occur.

 Rookie

If the water pump is ok, check your radiator for clogs and put 50/50 mixture of coolant(MB COOLANT) and distilled water, i havent experience reaching 120C on my s320 although im presently residing here is KSA where outside temp is around 35-55C. if the problems persist check your cylinder head.

* when the engine is cold it is normal that the RPM goes over 10 but when it reach its normal temp it will drop below 10, when your moving your steering wheel while on park and see's the RPM fluctuate that means your power steering pump is working. give a 1-2 minute delay before turning your A/C on.

or the best thing to do is bring your car to MB workshop for check-up.