Vacuum Leak Repair – Common Causes – Common Repairs

Vacuum Leak Repair
Vacuum Leak Repair

A vacuum leak repair is more common than you would think.

Quite often a vacuum leak will disguise itself as an ignition or fuel problem that is incorrectly diagnosed.

Also, an engine vacuum leak is always bad news because it allows “unmetered” air to enter the engine and upset the air/fuel ratio.

A vacuum leak can trigger a “check engine” light because the fuel system is running too “lean,” meaning it has a greater mix of air than is ideal.

For most people a vacuum leak repair is not that hard to do.

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

Vacuum leaks can develop in many locations, including the intake manifold, throttle body, emissions system and power brake booster.

Before you make any repairs confirm you have located any leaks.

For more help read our post on Vacuum Leak Detection – The Safe Way to Find Leaks.

The Following Is A List Of The Most Common Vacuum Leak Repairs:

Vacuum Leak Repair At Hoses And Fittings ( The Most Common Causes )

Leaking Vacuum Hose
Leaking Vacuum Hose

Before removing any hoses always label them along with their respective connectors or fittings. That way you will reinstall repaired or new hoses to their corresponding fittings. If a hose is rotten or hardened, it needs to be replaced.

The hose may chaff or rub against other components, or pull loose as a result of engine vibration. Use the correct type of replacement hose (PVC or vacuum hose capable of withstanding fuel vapors and vacuum without collapsing). Also, be sure the replacement hose is the same diameter and length as the original.

Vacuum Leak Repair At Carburetor Or Throttle Body Base Gasket

Try tightening down the carburetor or throttle body mounting bolts. If that doesn’t stop the leak, replace the gasket under the carburetor or throttle body.

While the carburetor or throttle body is off, use a straightedge to check the base and the manifold for straightness. Warped surfaces can prevent a tight seal, so if you find any it may need resurfacing or component replacement.

Vacuum Leak Repair At Intake Manifold Gasket

Try retorquing the intake manifold bolts, working from the center out in the recommended tightening sequence. If that fails, the intake manifold will have to be removed and the intake gaskets replaced. Sometimes the mating surface of the intake manifold or the heads will not be flat (check both with a straightedge). If warped, the intake manifold and/or heads will have to be resurfaced.

When replacing the gasket always ask if there is an upgraded gasket available. There are many aftermarket gasket suppliers that have made what they call a problem solver gasket. Also, Confirm if you need to replace the bolts as many are torque to yield on time use bolts.

EGR Valve Leaks

Sticking EGR Valve
Sticking EGR Valve

If the valve isn’t closing all the way due to carbon deposits, cleaning may be all that is needed. A common cause is your EGR Valve so always check it. Otherwise, the engine will need a new EGR valve.

Power Brake Booster Leak

First make sure it is actually the booster and not just the hose or check valve that is leaking. If it is the booster it is best to just replace it.

Other Sources Of Vacuum Leaks Include:

  • Actuators
  • Solenoids
  • Fuel pressure regulators
  • Secondary air injection valves
  • Purge valves
  • Door locks
Fuel Pressure Regulator Hose
Fuel Pressure Regulator Hose

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Conclusion

The most common symptoms of a vacuum leak are rough/high idle, misfires and a check engine light. Although vacuum leaks can be a pain, most of them are easily repairable. Periodically check your vacuum lines as over time they will start to get hard and brittle and start leaking.

Lean mixtures can detonate, damaging pistons and bearings. Higher than normal exhaust temperatures can also lead to catalytic converter meltdown.

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