Vacuum Leaks Repairs – How to Know if You Need Repairs
A leaky vacuum hose is a frequent cause of poor engine performance. Before we get into the various techniques of vacuum leak repairs, let’s quickly review vacuum’s role in fuel delivery.
Engine vacuum is vital for proper fuel delivery system operation; fuel injection systems need it to collect accurate information regarding the engine’s working conditions and to thus calculate the best fuel mixture for optimal fuel economy and power. If there’s a vacuum leak, then the computer must shoot for a “fuel rich” condition to prevent running lean, which could damage the motor with pre-detonation.
Sometimes a vacuum leak will whistle or hiss and make itself obvious. But oftentimes, a vacuum leak will disguise itself as an ignition or fuel problem that defies diagnosis. Either way, an engine vacuum leak is bad news because allows “unmetered” air to enter the engine and upset the air/fuel ratio.
Here is brief list of the most common symptoms of a vacuum leak in a car.
Symptoms of a Leaky Vacuum Hose
Rough Engine Idle
The classic sign of a car with an engine vacuum leak is a rough engine idle. A vacuum leak causes a disruption of the normal vacuum that is created from a running engine. A vacuum leak alters the vacuum pressure of an engine and the car’s engine speed will fluctuate up and down as the engine’s computer struggles to find an equilibrium. Upon acceleration, the car will lack power and respond slowly to throttle input. You will also notice a decrease in fuel mileage because the engine computer will be adding extra fuel to the cycle in order to avoid lean detonation. If your car’s motor is displaying these symptoms, a bad vacuum line may be to blame.
A vehicle with a vacuum leak will often have poor acceleration and reduced engine power. This is due to the leaking engine vacuum that reduces the overall force and pressure produced by the engine during combustion. During acceleration, the leaking engine vacuum pressure is more pronounced, which presents itself as a stumbling, or hesitating, engine. Engine hesitation can also be caused by a weak or inoperative accelerator pump in a carburetor, dirty injectors, or even ignition problems such as a cracked coil, worn spark plugs or incorrectly gapped plugs. Your mechanic will be able to diagnose exactly what is the cause of the problem.
Imprecise Transmission Shifting
Engine vacuum provides a large of a transmission’s operational power, which helps to properly shift the transmission gears. An engine vacuum leak can cause weak or imprecise transmission shifting points thereby requiring vacuum leak repairs.
Hard Vehicle Starting
Depending on the size and location of a vehicle’s vacuum leak you may experience hard vehicle starting as a result of a vacuum leak. By reducing the optimal pressure and vacuum within a working engine, a vacuum leak can inhibit the action and function of a car’s carburetor and/or fuel injection system, which then directly affects vehicle starting.
What Are The Most Common Causes Of An Engine Vacuum Leak
Improperly Installed Or Loose Vacuum Fittings
A poor connection is the most frequent cause of a car vacuum leak. To combat this problem, your mechanic will examine all of the connections on your vacuum lines, moving in sequence from one connection to another, as well as visually examine and physically handle each fitting to check for correct installation.
Ruptured Or Failed Vacuum Line or Vacuum Hose
As they age, vacuum lines may become weak or brittle, causing a leak. Alternatively, friction from your engine’s vibration may wear down a vacuum line and eventually cause it rupture. Your mechanic can repair this problem by replacing the length of the leaky line with a new vacuum hose. You can be assured in knowing that your mechanic will use the correct type of replacement hose (PVC hose or vacuum hose capable of withstanding fuel vapors and vacuum without collapsing).
Failed Or Broken Connectors
Over time, the plastic connectors in your engine compartment can degrade and crack, often breaking off where the vacuum hose attaches to it. To repair such a connector, your mechanic will replace it with a matching connector and trim the adjacent hoses so that they fit. To avoid a repeat of this problem, consider asking your mechanic whether you should use metal type connectors, which are more durable under stressful conditions such as engine heat.
Failed Gasket At The Intake Manifold Or Plenum
Less common – but also problematic, a bad gasket in these locations can also cause a vacuum leak. Since the gasket seals the hard components of the intake to keep the system free of outside air, a failed gasket usually causes immediate, severe problems with the operation of your engine, and must be replaced.
Your mechanic may be able to fix the vacuum leak by tightening down the carburetor or throttle body mounting bolts. If that doesn’t stop the leak, he may replace the gasket under the carburetor or throttle body. If there is a heat insulator or adapter plate under the unit, it may also have to be replaced depending on its condition. While the carburetor or throttle body is off, your mechanic will use a straightedge to check the base for flatness (and the manifold, too). Warped surfaces can prevent a tight seal, so if your mechanic finds any he may speak to you about resurfacing or component replacement.
EGR Valve Leaks
If the valve isn’t closing all the way due to carbon deposits on the stem or valve seat, cleaning may be all that is needed to cure the problem. Otherwise, your engine may need a new EGR valve.
Leaky Power Brake Booster
If your power brake booster is leaking, your it will cause a vacuum leak and your mechanic will have to replace it.
How To Fix An Engine Vacuum Leak
Whatever the cause of your Vacuum Leak, your mechanic may use a variety of methods to find the lead, including using a smoke machine, exhaust analyzer, and / or using pressure or electronic vacuum leak detection techniques. The technique used will depend on the make and model of your car and the mechanic’s experience and instinct in identifying vacuum leaks of your specific nature.
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