I have a 99 Freightliner truck with a 24v ISB. The crankcase vent is just a 3/4 steel draft pipe that ends in the airstream from the fan, this way there is still some draft when the engine is idling and the vehicle is not moving. There is no bottle to catch oil. If I add a bottle will it interfere with the draft? Right now the underside of the engine and the transmission is coated with oil, I would like to keep it cleaner.

 

This is the standard exit location for the crankcase vent on an ISB. I don't think it's location behind the fan is designed to provide "draft" but rather to disperse the fumes. The bottle was added to keep whiners from complaining about drips on their driveway and does little to prevent the messy film on the front of the engine. If you've never seen the bottle before, it's merely a plastic bottle with holes punched in its side. The vapor can readily escape and deposit on the front cover as if it weren't there at all. The solution is to extend the hose below the engine. Get some clear plastic tubing (it won't get gummy like heatrer hose will) and extend it down towards the road. This is what mostly everybody with a Ram does. Clamp it to the existing pipe and extend it far as possible. The advice I'd give you is to keeps the bends to a minuimum, and route it so there are no "traps" for water to deposit and freeze creating a plug.