Mercedes W124 noise from engine compartment
 

Start the car up and i get this noise .I thought it was from inside the glove box.The car is a right habd drive ,but on investigation i find its in the engine compartment, on the left by the suspension top .Its a square metal box with two small rubber conrctors and small bore vacuum hoses going in the top .. Any idea what the part is ? to me it looks like a switchover valve ..Any help would be fine ,,,,thank you for looking in .

A child or an adult; a stray cat or a gerbil; a wolverine or a hedgehog?