I have a 1998 Ranger ext cab. I love the truck except in the summer months I have a loud engine roar at low speeds. I check under the hood but I cant determine where the noise is coming from. Air can be on or off, I asked the dealer and they said its suction on the hoses. I flushed the radiator that didnt help. Any Ideas?

 

I had something similar to this, There was a rusted out hole in my exhaust. Just a thought to look there as well.

 

maybe its you fan. is it electric?