MB 380SE 1985 100,000 miles.
When I am driving around 40 mi/hr and still slightly accelerating I can hear whistling sound sort of like a kitchen kettle while boiling water. This sound is only present during light acceleration in the range of between 40-50 mi/hr. When I release gas pedal the sound stops immediately. When I apply pressure to the gas pedal the sound comes back.
Does anyone have any suggestions what this can be? Does it require immediate attention?