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    Thread: Finding vacuum leaks. Best way?

    1. Member briano1234's Avatar
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      90, 92, 93 Cabriolet They own you.
      10-06-2005 10:15 AM #26
      I refuse to let my cabby start smoking.....
      Grounds, Grounds, Grounds Replace them things.
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    2. Member nsmsam's Avatar
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      06-09-2007 05:34 PM #27
      Quote, originally posted by chef.stephen »
      A can of starter fluid.
      Spray it on any junctions or suspected leaks. If the idle speed increases you have a leak, simple.
      You probably won't see bubbles because the vacum lines are sucking air in not blowing out.

      Does starter fluid come in a spray can? or we put that into spray bottle ourself ?

    3. Member kamzcab86's Avatar
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      06-09-2007 10:54 PM #28
      Quote, originally posted by nsmsam »
      Does starter fluid come in a spray can?

      Yes.
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    4. Member Black_cabbie's Avatar
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      06-15-2007 05:46 AM #29
      wow, a 2 year thread bumped.....
      Chip Tuning for a living @ www.microchips-tuning.com

    5. 06-15-2007 03:17 PM #30
      If it is CIS - you might as well start replacing hose connections, injector seals, and idle by pass screw seal. It is likely that one of them is the culprit and if not now, they will be in the near future. I think you can get all the stuff to complete this for less that $30.
      Then put a dwell meter on the test port and adjust the idle mixture and you will be a happy camper.

    6. 08-04-2012 11:17 PM #31
      Meinit,

      You list the AC system as a possibility for a vacuum leak. The car I'm working on has normal vacuum with AC off (20" steady at idle, recovers quickly from snap test). But as soon as the AC is turned on it drops to 17" and then varies, sometimes drops as low as 13". It gets worse every time the fans come on, I believe the compressor is actuated every time the fans come on as well.

      I think I can hear the vacuum leak from near/inside the blower box but I can't figure out why there might be vacuum lines going in there since the air doors appear to be motor controlled.

      What is exactly the relation between the vacuum system and the AC system?

      PJ




      Quote Originally Posted by meinit View Post
      Quote, originally posted by Black_cabbie »
      Somebody told me to use a lighter. Just push the button and start moving it near suspected areas.... Are we looking to a cabriolet fireball here?

      How to: Fix Vacuum Leaks
      VWs are not generally cursed with the spaghetti of vacuum lines found under the hoods of many other cars. Nevertheless, vacuum lines are used in VWs and can cause trouble from time to time - creating the so-called "false" air syndrome.
      Air entering the engine that is unmeasured by the fuel injection system's air flow sensor is known as "false" air and will tend to lean out the engine's carefully controlled air-fuel ratio. Symptoms may include hesitation, bucking, poor throttle response, surging at small throttle openings and power loss. Serious vacuum leaks will play havoc with driveability as well as the operation of vacuum operated devices including power brakes, air conditioning vent flaps and power locks. A vacuum leak can occur anywhere there is a joint or fitting that connects directly to the intake air flow, along the length of any plastic or rubber vacuum hose, around a worn-out valve cover gasket or around the fuel injector seals. Especially look for hoses that may have chafed through from continually rubbing on something.
      Air Flow Sensor
      Start your hunt for vacuum leaks at the Digifant air flow sensor/air filter housing. Check the rubber duct between the air flow sensor and the throttle body for signs of splits or cracking. Cracks in the duct may only open up under acceleration when the engine torques rearward in its mounts. Remove the duct and inspect it carefully, twisting it in your hands (remember your gloves) while you look for cracks or splits. Reinstall the duct, making sure it seats correctly on the air flow sensor and the throttle body and that the hose clamps are not cocked or pinching the rubber when you snug them down. A light smear of clean oil on the metal mating surfaces can ease the installation of the duct.
      Temperature Regulator Valve
      The temperature regulator (or preheat) valve is located in the air flow sensor box above the air filter. The regulator valve's purpose is to control the operation of a flap in the air box which diverts heated air from around the exhaust manifold to the intake during starting in cold ambient temperatures. The regulator valve has two vacuum fittings which protrude through the side of the air box. A short vacuum line of white plastic runs from the lower fitting on the box to the diaphragm which controls the intake preheat valve. A longer vacuum supply hose runs from the upper fitting on the box to the throttle valve. A tee in this hose splits off to the fuel pressure regulator which is located at the right (passenger) end of the fuel rail. Check all of these lines for chafing, holes and snug connections.
      PCV Valve
      The positive crankcase ventilation valve (PCV) is another potential source of vacuum leaks. The PCV sits on the valve cover. The crankcase ventilation hose which connects to the PCV should be clean and free of cracks or splits. Follow the hose to where it connects to the throttle valve and make sure the connection is tight. The hose clamps should be in good condition and properly snugged down, but not so tight that they bite or cut into the rubber. Check the rubber grommet in the valve cover where the PCV mounts for a snug fit. The grommet should be free of cracks or other visible injury. See below for instructions on cleaning the PCV valve.
      Power Brake Booster
      With your engine off, step on the brake pedal eight or ten times to let air into the power brake vacuum booster. Now, hold down the brake pedal and start the engine. The pedal should drop slightly as vacuum builds in the brake booster. Vacuum leaks in the brake booster are exceedingly rare. Suspect other sources first.
      Other Potential Vacuum Leaks
      Evaporative Emissions Control Canister
      Air Conditioning
      Vacuum powered door locks
      Dipstick

    7. Member briano1234's Avatar
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      08-05-2012 03:25 AM #32
      Which model year are you talking about?

      As I under stand it, most of everything up to 93, are vacuum controlled there are no motors, Just Servos.

      If you hear a vacuum leak in the control area, then your vacuum distributor is faulty. Try to center the control to stop the hissssssss.
      Grounds, Grounds, Grounds Replace them things.
      Divorces, Great Coffee, and Electrics, all start with GOOD Grounds.

      Another Useless Ground Thread
      I am a Commodian. I tell really Crappy jokes.
      HAVE YOU CHECKED THE FAQ's ABOVE..PAGE 3 Thread 75?

    8. 07-09-2015 03:53 PM #33
      I've been researching on You Tube and other sights for days. I've heard a can of carborator cleaner is highly flammable and is not the safest method. If you do use this method have a fire extinguisher closer by. The best way seems to be with a propane cannister with a hose attached. You do NOT light the cannister. While the car is running and the cannister is on, you move it along the vacuum hoses, connections and seals. When you pass over a leak apparently the motor will start to run normal because the fuel/air ration returns to normal. I just changed all my plugs, wires and foots, and coil mechanism and my car still won't work. I believe its a leak and now have to go get a propane tank! I'll let you know how it goes!

    9. Member briano1234's Avatar
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      07-09-2015 09:48 PM #34
      Quote Originally Posted by kdq269 View Post
      I've been researching on You Tube and other sights for days. I've heard a can of carborator cleaner is highly flammable and is not the safest method. If you do use this method have a fire extinguisher closer by. The best way seems to be with a propane cannister with a hose attached. You do NOT light the cannister. While the car is running and the cannister is on, you move it along the vacuum hoses, connections and seals. When you pass over a leak apparently the motor will start to run normal because the fuel/air ration returns to normal. I just changed all my plugs, wires and foots, and coil mechanism and my car still won't work. I believe its a leak and now have to go get a propane tank! I'll let you know how it goes!
      Placing your year and model in your profile as well as the general area of the world that you live in goes long way in reminding us what you are working on.
      Grounds, Grounds, Grounds Replace them things.
      Divorces, Great Coffee, and Electrics, all start with GOOD Grounds.

      Another Useless Ground Thread
      I am a Commodian. I tell really Crappy jokes.
      HAVE YOU CHECKED THE FAQ's ABOVE..PAGE 3 Thread 75?

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