ongoing buzzing sound outside of car after 20 minutes of driving.

What is your question?

I am still driving my 1998 Ford Escort and overall very pleased but the last 5 years there has been a constant buzzing sound that only appears after 20 minutes of driving. Very loud, embarrassing and annoying. I haven't had it checked twice and know ones knows what it is. Afraid to have it looked at further for the labor/costs. The car is still running but the miles are piling up....looking forward to a new car soon. I have been told it could be an overworked bering....... ??