It depends on the border crossing. Usually you can import on Canadian side 24/7, but you must also export the car on the US side. Some US offices operate business hrs only - some 24/7 (only a few).
- Make sure you make and model can be imported
- Get a recall clearance letter from the dealer
- Fax the original title to the US border office 72hrs prior to export
- Get export documents/stamp for US border office
- bring title, and registration to the Canadian office
- Contact RIV to get the instructions on how to register your car in Canada. You may have to make certain modifications (km/miles, etc)
It's really straight forward