waterworks

Hi everyone, hope someone can answer this for me... To start with, the car is a 2004 ML270 CDI with full service history from same Indy for last 6-7 years, before I bought it recently. I'm preparing myself to change the thermostat - thanks for all the hints, tips & photo's from previous...

would anyone know what the little metal looking box behind the servo and below the windscreen is, i'm wondering if there is a chance of water getting on this unit and causing a slight missfire, it only happens after i have washed the windscreen or it is raining. thanks Rob