My hollowbody bass has a bowing neck and because attached to the body truss rod fix it so what can i do?

1. Check the neck relief. Use a straightedge or feeler gauge to check the gap between the bottom of the strings and the frets at the 7th fret. There should be a slight relief of about 0.010 inches or so.

2. Tighten the truss rod. If the neck is bowed in the direction of the strings, you need to tighten the truss rod. Turn the truss rod nut clockwise in small increments, checking the relief after each turn. Be careful not to overtighten the truss rod, as this can damage the neck.

3. Loosen the strings. If the neck is bowed in the opposite direction of the strings, you need to loosen the strings. Loosen the string tension evenly, checking the relief after each adjustment.

4. Heat the neck. If the neck is still bowed after adjusting the truss rod and string tension, you can try heating the neck. This can help to relax the wood and make it more pliable. Use a heat gun or hair dryer to apply heat to the neck, being careful not to overheat it.

5. Consult a professional. If you are unable to fix the bowing neck yourself, you should consult a professional guitar repairman. They will be able to diagnose the problem and make the necessary repairs.