Need Help!! Why saying non-manifold ?
 

I am going to simulate a Ford model T for my assignment. After I had drawn the CAD by using solidworks, I exported as parasolid. Then I import geometry and started using DM. When I want to create enclosure for my simulation, it keep saying "Operation would results in non-manifold bodies". I didn't use any surfaces for my drawing (00I guess, haha)

please help me and suggest any solution for this situation. Thank you very much.

Here are the project :

https://www.dropbox.com/s/6dmqjqnk7hnjzwc/CFD.rar