Vacuum Leak Detection – The Safe Way To Find Vacuum Leaks

Vacuum Leak Detection - The Safe Way to Find Vacuum Leaks
Vacuum Leak Detection - The Safe Way to Find Vacuum Leaks

A Vacuum leak can trick you, and your car computer, into believing a particular sensor or system needs fixing.

Then you start replacing components, hoping you’ll fix the problem, unsuccessfully.

Often, a vacuum leak makes an audible hissing sound, which makes it easy to find; other times, though, you won’t hear anything.

Therefore, many shops use special, costly equipment to detect a hard to find vacuum leak.

Vacuum Leak Detection Using A Smoke Machine

So, these machines feed artificial smoke into the intake manifold. You then look for smoke; seeping out of hoses, gaskets or cracks in the manifold, to find the vacuum leak.

Automotive Smoke Machine
Automotive Smoke Machine

Consequently, this type of equipment is often needed to find; small air leaks in the (EVAP) (evaporative emissions) control system. But, smoke machines can cost $600 to $2000 or more, depending on the model and features. So, they are primarily for use, by professional technicians.

But, before you head to the shop, you can apply simple techniques used; to track the most common vacuum leaks.

Intake Manifold Vacuum, Where Does It Come From

Vacuum exists in the intake manifold as a result of, the pumping action of the engine’s pistons. As well as, the restriction created by, the throttle valve. Consequently, were it not for the throttle choking off flow of air into the engine; there would be little, if any vacuum in the intake manifold.

Common Symptoms:

  • Backfiring
  • Hesitation
  • Hard starting
  • Low engine power
  • Engine Misfiring
  • Poor fuel economy
  • Poor acceleration
  • Rough idle
  • High idle
  • Stalling
  • Stumbling
  • Check engine light (CEL) on
  • Poor brake performance (on vacuum-type power brakes)

Keep in mind that these symptoms are not exclusive of a vacuum leak, since:

For example, may cause one or more of these symptoms as well.

To Find A Vacuum Leak, Always Start Off With A Visual Inspection

Okay, now that we have covered what vacuum leaks do; how do you find components that leak vacuum? One way is to visually inspect all the vacuum hoses and connections. Look for disconnected, loose or cracked hoses, broken fittings, etc.

Leaking Vacuum Hose
Leaking Vacuum Hose

Vacuum leaks are often the elusive needle in a haystack. If it is not a hose leaking vacuum; but something else such as a gasket, worn throttle shaft, injector O-rings, etc.; you may never find it using this technique.

Find Leaks By Applying Air Pressure – The Soapy Water Test. (The same way we used to find leaks in tires)

The safe way to find an elusive vacuum leak; is to pressurize the intake manifold with about three lbs. of regulated air. This can be done by attaching a regulator to your shop air hose; then attaching the hose to a vacuum fitting or the (PCV) valve fitting on the intake manifold; carburetor or throttle body.

Above all, Do not apply too much pressure or you may create new leaks!

With the engine off and air flowing into the manifold, spray soapy water on suspected leaks.

Spray Soapy Water On Suspected Leaks
Spray Soapy Water On Suspected Leaks

Consequently, If you see bubbles, you have found the leak.

The Common P2282 Engine Code:

How serious is the P2282 code?

Code P2282 is an indication that the (ECM)/(PCM) detects a vacuum leak and unmetered air; is getting into the engine. As a result, causing a lean idle condition. Hence, this could cause, stalling and emission test failures.

What repairs can fix the P2282 code?

  • Replacing the (PCV) valve.
  • Replacing the evap purge control valve.
  • Repairing vacuum leaks, in the intake manifold or throttle body.
  • Replacing or repairing vacuum lines that are, cracked or broken and leaking.


So, code P2282 is a code that indicates, there is unmetered air getting into the intake system. If no leak is found externally, then you may have an internal leak. You could have a intake valve that is not sealing in one of the cylinders. This is not very common, but one should be aware of this possibility.

Finally, doing a cylinder leak down test or compression test may be needed, to diagnose it correctly.

Thank You !