Ford 2003 Mustang Workshop Manual page 2967

4. Separate the fittings.
Clean and inspect the fittings for damage.
Connect
1. NOTE: Lubricate the tube end with clean engine oil to ease assembly.
Connect the fitting.
Align the tube to the fitting and push until you hear a click.
2. Pull on the fitting to make sure it is fully engaged, then install the safety clip.