How to detect an engine vacuum leak?

Every now and then i hear a hissing sound coming from engine, and im pretty sure its a vacuum leak. Plus rough idling, loss of power, fouled spark plugs and one cylinder not firing.

Im confused and most people say its a vacuum leak / head gasket ?

9 Answers

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  • 1 month ago
    Favorite Answer

    First off start the engine, open the hood, and try to pinpoint where the hissing noise is coming from. This will help you figure out where the leak is specifically. 

    Look for detached or broken hoses. If you suspect that you have a vacuum issue its a good idea to look over the engine for obvious problems. Look for hoses that are detached on one end and hoses that are shredded or clearly cracked. If you spot a problem like this than that is likely the cause of your engine problems.

    The number of hoses your engine has and their locations vary widely depending on your specific engine. Use a flashlight while you are looking at your engine so that you can see as many areas as possible. Small cracks in a hose can cause a vacuum leak. A visual inspection may not be able to find this type of small leak. What I do is use starter fluid or brake cleaner fluid. I spray a little at every vacuum connection and along the hoses with the engine running. When you hit a leak the engine will rev up slightly. It can also be a vacuum leak at the brake booster which would make the brake pedal harder to push. Remove the hose connecting the brake booster and plug the hose with your finger. If the hissing stops and engine smooths out you have a defective brake booster. 

  • 1 month ago

    One way is to use thick soapy water and spray it over anywhere you think the leak is coming from I fitted a new carburettor and found that the Phononic block was warped but looked ok the soapy water caused the engine to run faster a piece of glass and wet and Dry Fixed the Problem

    if it is a head Gasket a leak down test is the best Check

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  • 1 month ago

    Spray carb cleaner on those vacuum lines while its running. But keep a fire extinguisher with you when you do it. 

    Source(s): 79
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  • 1 month ago

    Don't start trying to guess. Find a good mechanic and have them tell you what's needed to keep your vehicle running right.

    Source(s): Mitsubishi Master Tech
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  • 1 month ago

    A vacuum leak would be constant and the check engine light would probably come on before you noticed any symptoms.

    • Anon
      Lv 6
      1 month agoReport

      May not HAVE a CE light. Some do not come on or engine will run rich to compensate.

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  • Anonymous
    1 month ago

    You can rent or buy a smoke machine at major car parts stores.  The machine can detect vacuum leaks in 5 minutes.  Scotty Kilmer even says you can use a cigar lol.

    https://www.youtube.com/watch?v=zMok2y05jNE

    Youtube thumbnail

    • STEVEN F
      Lv 7
      1 month agoReport

      A smoke machine would LOCATE, not merely detect a vacuum leak in under ONE minute.

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  • 1 month ago

    A vacuum leak will usually cause a car to idle poorly. It will not foul a sparkplug or cause a cylinder not to fire.

    • Anon
      Lv 6
      1 month agoReport

      Can cause hard starting, poor running, lean condition . Even prevent secondary from opening. 

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  • 1 month ago

    A very simple rubber tube which is allowing air into the system can cause all kinds of performance issues. What are the best tools in detecting these kind of leaks instigate yourself a smoke injector this device injects smoke into your vacuum line and you sat there and you watch to see where the smoke comes to pouring out and then you know where your vacuum leak is.

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  • 1 month ago

    get an OBD scanner

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