secondary air injection ventyre 2000

[stomana]

Chevrolet Venture 2000.
When i start cold engine the secondary air injection sustem starts to inject fresh air directly into the exhaut manifolds, bat dosent stop when the engine becomes hot.I hear sound from side on the air pump left will.When i pulled a smoll pipe from the valve (front)(part#24508523)i heard vacum saund for second and air pump stopes.Wat can i do to make the system normal.