Raining on the inside!

Not all that familiar w/Cascadias--but if you have already sealed clearence lites--anything else attached up there has to be looked at--am/fm antenna perhaps? air horn(s)--otherwise only option I know of is to remove headliner and follow water trail--'Good Luck

 

Bad Glue/Seal on the Windshield Edge?

 

Check your air horns if they're mounted up top. Although I don't drive a freightliner but my pete did the exact same thing. Some RTV around the air horn's and it's dry now. It don't have to be pretty, and you may want to tear the headliner out to check for the leak as mine appeared to be sealed at the outside as well but when we pulled the headliner and it was like the Missouri river in my cab.

 

Water can track in funny paths. The source of the leak could be quite far away from where actually see the water coming in. I may be coming from the back of the cab roof and running down the inside roof to the windshield headliner area before it drips out. Also, it make take 20 mins or more between the time the water actually gets in and to the point where it drips out.

 

It doesn't take much of a hole either! I had a trunk leak on a GM car once, couldn't find it, but was getting a lot of water in there. Finally got in trunk with a flashlight and closed the lid and had someone spray the outside with a hose, turned out to only be a pinhole in the body putty, but enough that lots of water got in, water leaks can be a pain to locate! As others have said, it is likely you will need to pull the headliner, etc. out and spray with a hose and see what you can find. Sometimes too, leaks only manifest themselves underway, when the vehicle is parked dry as can be since you don't have the wind driving the water into the place that is actually leaking.

TS

 

I drove a 2010 Cascadia that did the same thing. Told the owner of the truck...he didn't seem to care, so I stopped caring at that point as well. Was never looked into, so have no clue what it was.