Diesel Fume and ding ding noise
 

Hi again, my 1990 350 sdl has the regular diesel clunk clunk, but recently after returning from vacations (6weeks) it now throws out a ding ding noise every so often, weirding me out. Also I have noticed diesel fume smell in the cabin and thanks to this crazy winter weather have noticed fume coming from under the hood. I have replaced the O rings, so it aint that, but I`m worried that maybe somewhere along the exhaust line it might have a hole. Its always rough in the morning but after warming up it runs the same. Also keep having a thuink sound at 20, 40, and 60 or so klicks. Anyones help would be greatly appreciated.
Thanks