1. Find Your Vacuum Diagram:
* Owner's Manual: Your best bet is the original owner's manual. It *should* have a vacuum diagram.
* Shop Manual: A factory service manual (often available online or from specialty shops) is an even better resource. It will have detailed diagrams and explanations.
* Under the Hood: Sometimes (though rarely on older cars) a sticker with a simplified vacuum diagram is located under the hood.
2. Identify Components:
Before you start, identify all the vacuum-operated components:
* Power Brake Booster: Usually a large canister near the firewall.
* Distributor Advance (if vacuum-controlled): Located on the distributor itself.
* HVAC System (if vacuum-operated): Controls airflow and heat/AC.
* Transmission (if vacuum-controlled): Some transmissions use vacuum for shifting.
* Other Accessories: Some cars had vacuum-operated things like wipers or locks.
3. Trace the Lines:
Carefully examine the existing vacuum lines. See where they go and which components they connect to. Take pictures or make notes. Even small differences in routing can cause issues. Look for labels or markings on the lines themselves or nearby components.
4. Color-Coding (if applicable):
Some vacuum lines might have different color codes indicating their function. Refer to your diagram to understand the meaning of each color.
5. The General Approach (Use with Caution!):
If you can't find a diagram, you'll have to use careful observation and deduction. This is risky, as incorrect connections can lead to poor performance or damage.
* Power Brake Booster: This is usually the primary vacuum source, receiving vacuum from the intake manifold.
* Prioritize Essential Systems: Connect the power brake booster first, as this is crucial for safe braking.
* Follow the Lines: Try to trace the lines from the booster to other components. Look for T-connectors which split the vacuum to multiple parts.
* Use the Correct Size Tubing: Vacuum lines come in different diameters. Replace lines with tubing of the same size to maintain proper vacuum pressure.
6. Testing:
Once you've connected the lines, start the engine and listen for any unusual sounds (hissing). Test the vacuum-operated components (brakes, transmission, etc.) to make sure they are working correctly. A vacuum gauge can be helpful for measuring vacuum pressure.
Important Warnings:
* Incorrect connections can severely impact your vehicle's safety and performance. Do not attempt this without a diagram if possible.
* Vacuum leaks can cause poor engine performance and even damage. Make sure all connections are tight and the tubing is in good condition.
* If you are unsure about anything, consult a qualified mechanic. This is more than just "connecting lines"—a misunderstanding can cause problems.
Finding that diagram is the key. Do your research before you start messing with the vacuum lines on your 1971 Coronet.
