check coolant light keeps coming on on 2001 Mercedes-Benz E430 4MATIC

my e430 check coolant light keeps coming on in the vehichle i have put a new radiator in it a new thermostat new hoses new resevore tank and today the check coolant sill came on. no leaks check yo see if oil tank and dipstick had a gray milky color none of that was visible what do i check now

Asked by for the 2001 Mercedes-Benz E430 4MATIC
It could have just been all of the air in the coolant system finally worked it's way out of the engine, radiator, etc. and in to the coolant expansion tank. Although, I have done many water pumps on those vehicles. Look behind the water pump pulley for white stains or signs of leakage. It is the large pulley, in the center of the engine. You will be able to see behind it with an inspection mirror(you may need a flash light). Also, check around the pump/engine block sealing area for signs of leakage with the mirror. If you are having difficulty locating the water pump, follow the lower radiator hose from the radiator to the water pump. In addition, while you're looking around, check that the hose clamps are tight.