Using a Mity-Vac...

[Bryan Gunn <bgunn@voicetek.com>]

Hi folks,

Here's how to use a Mity-Vac to find vacuum leaks:

1. Put a length of the clear vinly tubing onto the nozzle of the mity-vac.

2. Put one of the cone-shaped fittings on to the other end of the tubing.

3. Stick your thumb over the end of the cone fitting and pump the mity-vac
   a few times to make sure everything up to the fitting is sealed.

4. Starting at your intake manifold or plenum or wherever the vacuum lines
   SOURCE of vacuum is, take the line off your engine and plug the mity-vac's
   cone fitting in to it.

5. Pump the handle until you have pulled enough air out of the line to simulate
   engine vacuum.

6. Watch the gauge on the mity-vac. If the needle hold still or drops verrrrry
   slowly, the line is ok. If the needle drops fairly quickly or you can't 
   even get the needle to come up off its stop, the line is leaking.

7. If the line is leaking, examine where the cone fitting goes into the line.
   Make sure it isn't leaking at this junction.

8. If the junction is OK, follow the vacuum line to it's next junction.

9. Disconnect this junction, connect the mity-vac, and repeat from step 5.

10. If the line is still leaking, keep following it. You will eventually 
    find the leak.

Once you find the leak and repair it, keep testing with the mity-vac as you
reassemble. The vacuum system in question could be leaking in more than one
place.

Advantages to using the mity-vac:

The vacuum distribution block on the intake manifold places all the lines 
really close together. If you spray this area with WD40 or whatever and the
idle does fluctuate, how do you know which line it was?

Suppose the leak is in the cruise control disengage vent on the clutch pedal
or the rear differential lock. You can spray the engine with as much WD40 as
you want and you'll never detect the leak. So you'll think your car doesn't
have vacuum leaks and start chasing other things. Massive frustration follows.

I've gone over my car from stem to stern with the mity-vac and have found 
vacuum leaks in really weird places. There's no way I would have been able
to find them otherwise. Or to quote PDQSHIP: "BTDT".

Later,

-- 
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*            Bryan Gunn                  Email: bgunn@voicetek.com           * 
*            Voicetek Corporation          Tel: 508.250.7998                 *
*            19 Alpha Road                 Fax: 508.250.9378                 *
*            Chelmsford, MA  01824                                           *
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