* Online Repair Manuals: Sites like Haynes or Chilton offer repair manuals for many vehicles, and some may include vacuum diagrams. However, the level of detail varies. Search specifically for a "1988 Cadillac DeVille repair manual" on their websites or on Amazon.
* Factory Service Manual: This is the best option but often the most expensive. A factory service manual (FSM) is a comprehensive guide provided by the manufacturer (General Motors in this case). You might find a used one on eBay or other online marketplaces, but be prepared to pay a significant amount. These are typically the most detailed and reliable source.
* Online Forums and Communities: Dedicated Cadillac forums or classic car forums might have members who have scanned or photographed their vacuum diagrams and would be willing to share them. Search forums like Cadillac Owners, or general automotive repair forums. Be prepared to be specific in your search terms (e.g., "1988 Cadillac DeVille 4.5L vacuum diagram").
* Local Auto Parts Stores: While they may not have a printed diagram readily available, some auto parts stores have access to online databases or repair information. It's worth asking if they can look up a diagram for your specific vehicle.
* Professional Mechanic: A mechanic specializing in older Cadillacs will likely have access to the necessary diagrams, either through their own resources or subscriptions to online databases. This might be the easiest route, but you'll have to pay for their time.
Important Considerations:
* Engine Size: 1988 DeVille's came with different engine options (e.g., 4.1L, 4.5L, 4.9L). Specifying the engine size in your searches is crucial for finding the correct diagram.
* Diagram Complexity: Vacuum systems in older cars can be complex. Even with a diagram, understanding how it works might require some automotive knowledge.
Remember to always be cautious when working with vacuum lines. Incorrect routing can affect engine performance and even cause damage. If you're not comfortable working on your own vehicle's vacuum system, it's best to consult a professional mechanic.
