Vacuum leaks on automotive engines and related systems can play havoc with all sorts of things, including engine performance and fuel mileage. Once you determine you have a vacuum leak, pinpointing it can be a long, frustrating process unless you know few simple tricks that will help narrow it down quickly. Once you detect where the leak is, make sure to repair it immediately. Anyone with basic automotive repair skills can perform this troubleshooting procedure.
Start the engine and open the hood.
Put your safety glasses on and spray the carburetor cleaner in a quick, short burst at the vacuum lines. Move along the lines, inch by inch, spraying in quick short bursts. Once you hit the leak, the engine idle will change momentarily in response to the carburetor cleaner drawing into the leak.
Spray along the intake manifold gaskets, where the intake manifold seals to the engine and heads. You will need the inspection mirror and flashlight to work your way around the intake, especially along the back side. Once again, you are listening for any change in engine idle.
Shut the engine off once it reaches operating temperature. If you have not found the leak by this time, wait several hours and try again once the engine cools down. Vacuum leaks often self-seal when the engine reaches operating temperature and components swell slightly from the heat.
