The reservoir level drops below min and the warning like comes on but after I add coolant, it goes out. I moved the car, jacked it up and crawled under to look. The device in question is to the lower front of the engine. It was still vibrating 10 minutes after shutting off the engine but then stopped. There was evidence of leakage on the screw heads and attaching hose. Does someone know what this device is and how difficult it is to replace? Thanks!!

Cars & Trucks - Volkswagen - GTI - 2003 Volkswagen GTI