Just picked up my 95 300d from mercedes shop for glo plug replacement, new serpentine belt and a new disc. When taking the car above 40 mph, there is a loud siren like sound coming from the driver's side of the dashboard. No warning lights come on inside the car. When slowing down, it diminishes. Driving around town, this does not happen, only on highway. Could the mechanics have loosened one of the wires while they were in there? and, more importantly, is it dangerous to drive it?