Sorry, this article is currently incomplete. We'll have this finished up soon. In the meantime, check out some other articles on Cars Simplified!Vacuum leaks usually cause a high pitched (but not very loud) hiss or whistle sound. A vacuum leak lets more air in than the engine expects. You can find them by covering up suspected leak points around the intake after the throttle body. Intake leaks can come from bad gaskets, cracks in the intake manifold, or parts within the vacuum portion of the system not being connected properly.
How to Find a Vacuum Leak by EricTheCarGuy
Vacuum Leak Tools & Supplies
Carb/Throttle Body Cleaner
This combustible fluid has the danger of being ignited if used around a hot engine or improperly, but the combustible nature is important to hearing the engine RPM change when it is sprayed on/near the leak.
Fire Extinguisher
Because you are working with flammable chemicals, this safetly item is critical! Do NOT attempt this job without one.
Propane Torch
An alternative to carb cleaner, it is still dangerous but it can be used to do the same job.
Step 1: Listen For a Leak
Vacuum leaks often make a high pitched hissing sound, and if you can figure out at least a general area where that sound is louder, you'll have a better idea of where to conduct further testing in the next steps.
Step 2: Touch Test
As long as the engine isn't hot, you can run the engine and touch flexible hoses to see if any of them affect engine speed. Moving a hose or other vacuum item will potentially make the vacuum leak opening larger or smaller, changing the RPM of the engine thanks to there being more or less unmetered air coming into the engine.
Step 3: Identify The Leak Point
Using carb cleaner or carb cleaner, spray some flammable gas near the leak to narrow down the exact location of the leak.
Step 4: Determine Your Repair Method
Once you know what is leaking, figure out how you want to repair it. If it's easy enough to replace, you may be able to buy the part and do it yourself. Sometimes all it takes is a small length of the right size vacuum line, while other times it may require the modification or replacement of an expensive, hard-to-get-to part. If you're not comfortable doing the repair yourself, have a professional do it.