* Brake Booster: A large vacuum line connects to this, usually near the firewall.
* Intake Manifold: Lines often branch off from the intake manifold to supply vacuum to different systems.
* Transmission (if applicable): Some transmissions use vacuum for shifting.
* Various Emission Control Components: EGR valve, purge solenoid, etc.
* HVAC System: For climate control actuators.
To find them, you'll need:
1. A Repair Manual: A Haynes or Chilton manual for your specific year and model Avalanche will have diagrams showing the vacuum lines and their routing. This is the best resource.
2. A Close Inspection: Carefully examine the engine bay. Vacuum lines are typically thin, often black or colored plastic tubing. Look for lines running to the components listed above.
3. Trace the Lines: If you find one end of a line, follow it to see where it connects.
Caution: Be careful when working with vacuum lines. They are often brittle and can easily break. If you need to replace any, use vacuum-rated tubing of the correct diameter. Incorrect routing can lead to serious drivability issues or malfunctioning systems.
