Vacuum Leak Test
How to Locate an Engine Vacuum Leak
An engine generates vacuum when
running, this vacuum is used to operate several accessories from the power
brake system and temperature control
systems (heater,
air conditioner) including
the cruise control. The pistons
create vacuum on their downward slide which allows air and fuel to be delivered
into the combustion chamber. Once delivered, the mixture is ignited, there is an
explosion, and the piston is forced back down creating power. For the engine to
run properly, the correct air and fuel mixture needs to be delivered to the combustion
chamber. When you have a vacuum leak, the air/fuel ratio becomes incorrect and can
cause many problems. Most common problems are,
low idle,
high idle,
poor acceleration,
cylinder misfire and
stalling at idle. There are many components
that require vacuum, however, most commonly, vacuum leaks are usually the result
of a dry rotted or disconnected rubber hose or a
failed intake gasket. Testing
a vacuum source is simple, remove the vacuum line from any giving accessory and
attach the vacuum gauge. Start engine and allow to idle, the gauge should read between
14 and 18 inches of vacuum. If a low or no vacuum exits there is blockage or breakage
of a vacuum line. Inspect all vacuum line integrity, then remove vacuum line from
the engine source and check for blockage, repair as needed and recheck the system.
If you are experiencing a problem with the air flow direction of the ventilation
system, make sure to check for vacuum leaks under the dashboard of the vehicle.
Additionally, if you are concerned about using carburetor and choke cleaner to locate
a leak, you can try pinching the different individual hoses to see if there are
changes to the engine idle speed. When checking for a vacuum leak use an aerosol
carburetor cleaner like Gumout or Berryman can be useful. When an engine burns this
additional flammable liquid it will raise the engine idle slightly. When the cleaner
is completely digested into the engine it will return to its normal, malfunctioning
condition. These cleaners are flammable so use them with caution.
Start with your car parked on level ground with the engine warm but not hot. Set the parking brake to prevent the car from rolling, also wear protective eyewear, gloves and clothing.
Tools Needed
1. Carburetor/Choke cleaner
2. Fire extinguisher 3. Replacement vacuum hose 4. Needle nose pliers 5. Screwdriver set
Directions
Step 1 - Open the hood and do a visual inspection. Check for broken or disconnect rubber vacuum hoses. Also, some vehicles actually use a small plastic hose which commonly break.
Step 2 - If the vehicle passes the visual inspection, start the engine and listen. You may hear a hissing sound generated from a vacuum leak that will help you pinpoint the malfunction.
Step 3 - If you are unable to hear any noise or locate it directly, you will now need to begin using the carburetor cleaner. WARNING: Carburetor and choke cleaner is flammable. If the product makes contact with a component, such as an exhaust manifold, that is hot enough, it can start a fire. Keep a fire extinguisher near you while you perform this test for safety.
Step 4 - Using the carburetor cleaner, spray around the intake manifold gasket and on all vacuum lines. Also, make sure to spray the PCV valve vacuum supply and all EVAP vacuum system vacuum hoses.
Step 5 - When the carburetor spray reaches the affected vacuum leak, the engine RPM’s will smooth out and change. They may increase. If that happens, pinpoint where the spray is going to identify where the leak is coming from and repair.
?
If further assistance is needed, our certified car repair technicians are ready to answer your car questions. Also, gain manufacturer specific instructions and information by clicking - Auto Repair Manual Related Car Repair Information
Start with your car parked on level ground with the engine warm but not hot. Set the parking brake to prevent the car from rolling, also wear protective eyewear, gloves and clothing.
Tools Needed
1. Carburetor/Choke cleaner
2. Fire extinguisher 3. Replacement vacuum hose 4. Needle nose pliers 5. Screwdriver set
Directions
Step 1 - Open the hood and do a visual inspection. Check for broken or disconnect rubber vacuum hoses. Also, some vehicles actually use a small plastic hose which commonly break.
Step 2 - If the vehicle passes the visual inspection, start the engine and listen. You may hear a hissing sound generated from a vacuum leak that will help you pinpoint the malfunction.
Step 3 - If you are unable to hear any noise or locate it directly, you will now need to begin using the carburetor cleaner. WARNING: Carburetor and choke cleaner is flammable. If the product makes contact with a component, such as an exhaust manifold, that is hot enough, it can start a fire. Keep a fire extinguisher near you while you perform this test for safety.
Step 4 - Using the carburetor cleaner, spray around the intake manifold gasket and on all vacuum lines. Also, make sure to spray the PCV valve vacuum supply and all EVAP vacuum system vacuum hoses.
Step 5 - When the carburetor spray reaches the affected vacuum leak, the engine RPM’s will smooth out and change. They may increase. If that happens, pinpoint where the spray is going to identify where the leak is coming from and repair.
?
If further assistance is needed, our certified car repair technicians are ready to answer your car questions. Also, gain manufacturer specific instructions and information by clicking - Auto Repair Manual Related Car Repair Information