View Here : How To Check For Vacuum Leaks
If the engine reacts to this in any way -- for instance, by speeding up briefly -- then the fluid is slipping in through the leaks. All of these signs are a warning that you should be paying a visit to your local auto mechanic for a definitive leak check. There's a second way in which intake manifolds can leak.
How to find and repair a vacuum cleaner leak. It is normal that, over time, vacuums will go through wear and tear, particularly in their hoses. Over time, the hoses can form tears, cracks and holes that rob the cleaner of suction power. As the leak worsens the vacuum will perform more and more poorly.