Cadillac Repair: what is it, brake booster, loud noise

Question
1986 cadillac eld.makes a loud noise on the passager side under the hood,i cant see what it is but when i took out a fuse on the drivers side marked vac pump it stops so i guess thats it but is it something i have to have it runs unhooked?  whats its function? and of coruse hows it fixed?  thanks so much in advance for your help     red

Answer
It is an air pump and it pumps air into the air intake, mainly to ensure a sufficient vacuum for the brake booster is always there, and in the event that your engine suddenly stops it will still pump a vacuum for just a few seconds but usually enough so that the brakes can stop the vehicle with little effort.