Could any specialist of M Class gives me answers to my below questions:

I had the Radiator water light kept on suddenly and when i checked the water level and the coolant then both were 100% ok. i was told that this could be a sensor problem so i went on and bought a new water tank since the sensor comes attached to it. any how, when i changed it then the following happens:

1 - The radiator water light kept on and did not go out, is a way i could get rid of it, i bought a new original water tank that comes with the sensor but still the light is on.

2 - after fixing this water tank i had suddnely a new light came in (Check Engine) - i took the care of a car's computer specialist who tried to fix the problem and told me that this is because you changed the water tank so when i was at his shop and after he did the reset, the Check engine light went off although the water radiator light kept on. anyhow, he told me that there is a possibility that the sensor on my new water tank is not working proberly. after i left his shop the Check Engine light came on again.

The car is normal and nothing is wrong with it. How could i fix the above issues.

 

make sure you purge all the air out of the cooling system. run the defrost for a while until normal operating temp is reached and the thermostat opens up. and then check the coolant level again. i didnt think the MLs had a temp sensor in the tank but maybe something was left unplugged during the fix.