2. Apply some saliva or soapy water to the spool. If a bubble forms, the spool should be tightened with the back of the cap.
Attention! Only metal caps are suitable for tightening the spool. Metal caps are sold at gas stations.
3. Check the spool again. If a bubble forms again or the spool no longer tightens, it must be replaced.
4. Be sure to screw the cap back on.