# DIY: Find a Vacuum Leak



## 97VWJett (May 17, 2003)

Alright so credit to momovr6, local genius!
So if you have read around you will know that a boost leak = vacuum leak. Well, the idea behind this test is to create enough pressure until you hear/find a leak.
Here is what I used:
Valve Stem from tire
2" Qwik Cap (Lowe's and Home Depot carry these in the plumbing dept.)
ABA MAF (I kept this old dead one)
Drill and drill bit (forgot what size)
Air compressor
Tire Pressure attachment
Spray bottle with soap and water
Here is what to do:
1. Acquire at least the Qwik Cap or whatever it's called
2. Acquire 1 valve stem with a good shrader valve
3. Drill a hole the same size as the tip (where the cap goes) in the center of the Qwik Cap
4. Pull the valve stem through
5. Attach the 2" Qwik Cap with valve stem to the side of the MAF with the "grid" on it
6. Remove the boot/clamp from the MAF that is installed in the car
7. Attach your "pressure tester" here and tighten the clamp/boot onto the MAF
8. Using your tire pressure attachment, send compressed air into the engine. (I blocked the TB open by using a long screw driver and putting one end on the TB and the other on the exhaust manifold.)
9. Listen for leaks. If you suspect a leak, spray the soap and water around the area and look for bubbles.
I found a leak at the TB where the intake boot clamps onto the TB. Tightened the clamp, no leaks! I started to hear the oil cap leak a little too.
*Note, don't pressurized the system too much. You will pressurize the crank case. It won't take much to find a leak. I know my OPG is already leaking so I didn't care.










_Modified by 97VWJett at 12:16 PM 2-19-2007_


_Modified by 97VWJett at 12:04 PM 3-8-2009_


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## independent77 (May 23, 2003)

*Re: DIY: Find a Vacuum Leak (97VWJett)*

my $.02
Start Engine
Use a propane torch(do not light it.)-turn valve on....
Pass the nozzle around your intake tube, vac lines, and all intake connections...
The idle will rise/smooth out when the torch passes a 'leak'


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## 97VWJett (May 17, 2003)

*Re: DIY: Find a Vacuum Leak (independent77)*


_Quote, originally posted by *independent77* »_my $.02
Start Engine
Use a propane torch(do not light it.)-turn valve on....
Pass the nozzle around your intake tube, vac lines, and all intake connections...
The idle will rise/smooth out when the torch passes a 'leak'









Yeah you can use that or throttle body cleaner but it's a little harder while the engine is running to isolate noises.


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## McNeil (Jan 18, 2006)

This will come in handy, but what exactly is Qwik Cap?


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## 97VWJett (May 17, 2003)

*Re: (McNeil)*

It's a rubber cap that is used in plumbing? I will get a pic of the setup
Here is an image of the qwik cap by fernco

















_Modified by 97VWJett at 10:45 PM 2-11-2007_

_Modified by 97VWJett at 10:46 PM 2-11-2007_


_Modified by 97VWJett at 11:00 PM 2-11-2007_


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## McNeil (Jan 18, 2006)

Please post some pictures, I would love to use this to see if I am getting any boost leaks.


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## 97VWJett (May 17, 2003)

*Re: (McNeil)*


_Quote, originally posted by *McNeil* »_Please post some pictures, I would love to use this to see if I am getting any boost leaks.

Will do


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## 97VWJett (May 17, 2003)

*Re: DIY: Find a Vacuum Leak (97VWJett)*

Picture added


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## McNeil (Jan 18, 2006)

Thank you!


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## ctuagent117 (Oct 4, 2005)

seafoam? clean your fuel system WHILE finding a leak...now thats PEAMp


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## independent77 (May 23, 2003)

*Re: (ctuagent117)*


_Quote, originally posted by *ctuagent117* »_seafoam? clean your fuel system WHILE finding a leak...now thats PEAMp

what the hell are you talking about?


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## ctuagent117 (Oct 4, 2005)

if you have a hole in a vacuum line or something, and you use seafoam, doesn't it smoke out of that hole?


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## independent77 (May 23, 2003)

*Re: (ctuagent117)*

no.


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## ctuagent117 (Oct 4, 2005)

i've heard of ppl reporting that it does. Can anyone else comment on this?


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## independent77 (May 23, 2003)

*Re: (ctuagent117)*

why would smoke come from a vacuum leak? its a VACUUM leak, its sucking(not blowing smoke)
You are thinking of the throttle body cleaner trick...
(spray t-body cleaner where there are suspected vac leaks, and the cleaner gets sucked into the leak, and changes the idle.)


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## Mussen (Jul 1, 2006)

*Re: (ctuagent117)*


_Quote, originally posted by *ctuagent117* »_i've heard of ppl reporting that it does. Can anyone else comment on this?


SeaFoam will make your exhaust smoke.Fed into a vac hose it may help you find an exhaust leak.


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## engineman98 (May 31, 2008)

*Re: (Mussen)*

you can use a lit cigarette and hold it near the vacuum lines and see if it sucks the smoke in...


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## Ryan Carver (Feb 5, 2007)

*Re: DIY: Find a Vacuum Leak (97VWJett)*

How much pressure is too much pressure. I am troubleshooting a vacuum leak this week and am preparing tools + knowledge.


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## 97VWJett (May 17, 2003)

*Re: DIY: Find a Vacuum Leak (Ryan Carver)*

Take the oil cap off to avoid over pressurization.


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## Ryan Carver (Feb 5, 2007)

*Re: DIY: Find a Vacuum Leak (97VWJett)*

For a start - 1.8T (AWW). Oil cap off, maf connected to Quik Cap... Add pressure? Do I need to open the throttle? Should I stick wife in car (with key turned to first position) to press on the accellerator? Please advise.


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## 97VWJett (May 17, 2003)

*Re: DIY: Find a Vacuum Leak (Ryan Carver)*


_Quote, originally posted by *Ryan Carver* »_For a start - 1.8T (AWW). Oil cap off, maf connected to Quik Cap... Add pressure? Do I need to open the throttle? Should I stick wife in car (with key turned to first position) to press on the accellerator? Please advise.

If you have electronic throttle, yes you will have to hold the throttle open with someone in the car with the key on.
For pressure, keep it as low as possible. I'd say for your car under 10 psi if possible. A large vacuum leak will be easy to find.
The best tool would be a smoke machine or a bottle of propane with a hose on the end coupled with a scan tool to watch the fuel trim change.


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## Ryan Carver (Feb 5, 2007)

*Re: DIY: Find a Vacuum Leak (97VWJett)*

OK...... Oil cap loose, key off (no wife in car), TRIED to pressurize to 10psi, will not hold pressure & oil cap just flutters around on top as pressure leaks out oil cap. Suggestions? Is this symptom of bad PCV?
The pressure regulating valve (034 129 101 A, not the B revision) is all gooped up with oil. The suction pump (058 133 753 ?, don't know the revision, could be D) looks to be ok but I cannot see well enough to know. There is an oil leak on the right of the engine at the valve cover.


_Modified by Ryan Carver at 1:39 PM 3-11-2009_


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## GusDahBus (Feb 26, 2009)

Hey i dont have a extra MAF laying around, should i use the working one? or can i do it without a maf and just the qwik cap?


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## 97VWJett (May 17, 2003)

*Re: (GusDahBus)*

You can use your existing MAF. The qwik cap is made of out rubber and won't go on the boot very well. You could get a bigger cap for the throttle body directly.


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## 68redbug2000jetta (Sep 14, 2007)

i bought a 2" quick cap like exactly the one pictured and i can not seem to get the sucker to slide over the maf housing.what can i do?


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## Mspeedy3 (Jun 20, 2009)

Just a dumb question - Can u actually 'pressurize' the intake system, or does much air flow through open intake/exhaust valves?

Also, should much pressure make its way back into the crankcase and out the breather? If so, is this just due to a bit of air sneaking past the compression rings and thru the piston skirts? Im asking because Im not sure if one of my problems is a stuck-open PCV valve, off the TIP...

THNX


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